“rurfh

 

 

AND THE: [A FORTE, 1N DEAN " ; RAIN

sm'rwmvzas 4

meme».

V:
.;2

r'- w~pgv

 

 

 

   

 

 

     

   

   

 

   

 

     

‘ 2 ‘
" ‘ 2 » - .. ~ . \ 4 _
. ’ \- , . H
2
.\ ~ .. ‘ ‘ h \ ‘ ‘ ‘
, V » ‘ - . ‘ -- .
« w. .. \ : .

     

 
 

     

 

   
 
 

 
 

     

‘ 2 ;

 

 

 

 

     

 

 

.’.r.;,,
"fr r}. r.- ’ ’
u}

2.52.- rr1-fifl,’ "' " r; ,' ,‘fi::;;rfi_;l
.n 1-! m. : pry-2'12, 1. .
" '2'

7-5:” .2 )-.,,
_r'.« Jvfit‘30

, -..,-
" .- , "owl—Cari." 1"
r
* I . . rrfr we.” 3.4-»- -r.-yo ,- 2-.
'-*?.;so~“'::" 232'», . fl". ‘ w. ' r ;
Mfr—n; ' W
{C 79'

”I;
(/Mjéé‘fkf (if
firwrr 7'}?
’21:. {15; If??? v unified, '
3'5?” {r

".2223." 753
r .. mrrr'v-‘rg
2-2129?)-

 

 

 

 

 

 

 

 

 

 

 

  
   
   

  

I. [BRA R. Y *
IVii-si‘ngan State
University

This is to certify that the

thesis entitled

FOREST AND LABLE BhEEZE PATTEJHNS
AND THE LA FORTE, ITJDIANA, BAII‘TFALL ANCI‘CALY

presented by

Wallace M. Elton

has been accepted towards fulfillment
of the requirements for

PhoD. degree in GeOFzI‘aDhy

 
    

jor professor

 

0-169

 

ABSTRACT

FOREST AND LAKE BREEZE PATTERNS AND THE
LA FORTE, INDIANA, RAINFALL ANOMALY

By

Wallace M. Elton

A thirty-year pattern of anomalously high warm—season
precipitation centered on La Porte, Indiana, has recently
been attributed to atmospheric pollution by the industrial
complex in the vicinity of Gary, Indiana. The purpose of
the present study is to attempt to evaluate possible phyto—
geographic evidence that the La Porte anomaly pre-dates
the development of the industrial complex and to make a pre-
liminary test of an alternative hypothesis regarding the
cause of the anomaly. It is postulated that a lake breeze
front frequently lies near La Porte during summer days when
the regional surface flow has a westerly component. Con—
vergence associated with the front may lead to isolated
or augmented precipitation and produce greater seasonal
rainfall totals near the mean frontal position.

A forest composition survey was conducted during
August and September, 1969, along the Valparaiso morainic

system which trends northeast-southwest through La Porte,

Wallace M. Elton

Porter, and Lake Counties, Indiana, and passes through the
described rainfall anomaly. Mesophytic species, particu-

larly Fagus grandifolia (beech) and Acer saccharum (sugar

 

maple) were found to predominate in forest stands in La
Porte and eastern Porter Counties, the area subject to the
greater precipitation. In western Porter and Lake Counties,
more xerophytic species, including Quercus velutina (black
oak), g. albg (white oak), g. macrocarpa (bur oak) and
QEEXQ glabra (pignut hickory) dominated. Previous studies
compiled from historical records have verified the existence
of this pattern in the presettlement vegetation. These
findings suggest the presence of a long—term environmental
gradient.

A pilot survey of soil texture along the moraine was
also conducted. Samples collected from the B horizon and
from a depth of four feet indicated an increase in clay
content from east to west with a corresponding decrease
in the percentage of sand. It is believed that the greater
clay content to the west could reduce readily available
water capacity sufficiently to account for the absence of
mesophytic tree species. Therefore, it is concluded that
the forest contrast cannot be cited as strong evidence for
the presence of a long—term climatic gradient.

Wind data were collected from June 11 through
August 3l, 1969, at six stations in northwestern Indiana

and northeastern Illinois in order to test the hypothesis.

Wallace M. Elton

Analysis of wind direction records revealed twenty—two
days on which lake breezes apparently developed along the
southeastern shore of Lake Michigan under regional winds
from westerly azimuths, in spite of the general subnormal
temperatures of the 1969 summer season. During these days,
the lake breeze frequently penetrated to the vicinity of
La Porte, particularly when the regional flow was westerly
or northwesterly. Neither the number of observation sta—
tions nor the length of the study period was sufficient to
define precisely the mean position of the lake breeze front.
These findings tentatively suggest that the lake breeze
may be a factor in the regional precipitation pattern, par—
ticularly during periods of positive temperature departure.
Determination of whether the La Porte anomaly is in
fact related to lake breeze convergence would require de—
tailed examination of wind patterns on days of excess pre—
cipitation at La Porte over a longer period. It is doubtful
whether such an examination can be carried out through
examination of past records because these exist for only

three of the six stations available for the present study.

FOREST AND LAKE BREEZE PATTERNS AND THE

LA PORTE, INDIANA, RAINFALL ANOMALY

By

Wallace M. Elton

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Geography

1970

G:- 4,552.32
/<$O«7/

ACKNOWLEDGEMENTS

The author would like to thank the many individuals
who assisted in the completion of this research project.
Special appreciation is expressed to Professor J. R.
Harman, who provided valuable advice and encouragement
during all stages of the dissertation. Professors D. H.
Brunnschweiler and H. A. Winters offered helpful sugges—
tions and Professor E. P. Whiteside, Department of CrOp
and Soil Sciences, provided guidance with regard to the
soil survey and analysis.

Among the people who aided in various phases of this
project are: Mr. Robert A. Ward of the U. S. Weather
Bureau, Purdue University; Mr. H. Moses of Argonne National
Laboratory; Mr. D. L. Brubeck of Purdue University's
North Central Campus, Westville, Indiana; officials of the
Michigan City station of the Northern Indiana Public Service
Company; Dr. R. I. Dideriksen and Mr. F. W. Sanders of the
U. S. Soil Conservation Service, Indianapolis; and Mr. B.
Schrand, Service Forester, Indiana Department of Natural
Resources. Final drafting of the maps and diagrams was
done by Mr. J. D. Root. Many other individuals, too numer-
ous to mention, gave assistance which is gratefully acknow-

ledged.

ii

Financial support during completion of this project
was provided by a graduate fellowship from the National

Science Foundation.

TABLE OF CONTENTS

Page
ACKNOWLEDGEMENTS . . . . . . . . . . . . 11
LIST OF TABLES . . . . . . . . . . . . . v
LIST OF FIGURES. . . . . . . . . . . . . vi
CHAPTER
I. INTRODUCTION . . . . . . . . . . . 1
II. METHODOLOGY. . . . . . . . . . . . 111
III. THE PLANT GEOGRAPHY . . . . . . . . . 28
Physical Setting . . . . . . . 28
Review of the Literature . . . . . . 31
Forest Composition . . . . . . . . 36
Soil Patterns . . . . . . . . . . A7
IV. THE LAKE BREEZE . . . . . . . . . . 66
Review of the Literature . . . . . . 66
The Climatic Hypothesis. . . . . . . 7A
Results of the Survey . . . . . . . 79
V. DISCUSSION . . . . . . . . . . . . 105
VI. SUMMARY AND CONCLUSIONS. . . . . . . . 119
LIST OF REFERENCES. . . . . . . . . . . . 127
APPENDICES . . . . . . . . . . . . . . 139
I. Locations of Surveyed Forest Stands. . . 1A0
II. Total Number of Arboreal Stems Surveyed in
Each Stand . 1A1
III. Per Cent Sand, Silt, and Clay for Individual
Soil Samples . . 142
IV. Values of pH for Individual Soil Samples . . 1AA
V. Lake Breeze and Non— Lake Breeze Days at
Michigan City and Ogden Dunes, Indiana,
Examined in Chapter IV . . . . . 1A6

iv

LIST OF TABLES

Table
1. Per Cent Contributions of A11 Tree Species
to Stand Canopies. . . . . . . . . .
2. Occurrence of Shrub Species in Surveyed Stands
3. Mean Coefficients of Similarity Between Beech—
maple, Oak—hickory, and Contrasting Stands
A. Two Measures of Comparison Between Forest
Types.
5. Average Percentages of Sand, Silt, and Clay
in Soil Samples From Surveyed Forest
Stands . . . . . . . . . . . .
6. Correlations Between Tree Species and Soil
Characteristics . . . . . . . . . .
7. Number of Occurrences of Wind From Sixteen
Directions During Twenty-two Lake Breeze
Days: 1000 EST . . . . . . . . .
8. Number of Occurrences of Wind from Sixteen
Directions During Twenty-two Lake Breeze
Days: 1300 EST
9. Number of Occurrences of Wind from Sixteen
Directions During Twenty—two Lake Breeze
Days: 1600 EST
10. Summer Precipitation and Temperature Data for

La Porte and Valparaiso, 191A—1969

Page

38
39

42

AA

“9

52

83

8A

85

108

Figure
l.

J:

O\

10.

11.

12.

13.
1A.

15.

16.

LIST OF FIGURES

Mean June—August Precipitation in North—
western Indiana, 1956—1960 . . . . . .

Location of the Study Area . . . . . .
Location Map of Study Area . . . . .
Location of Surveyed Forest Stands . . .
Location of Instrument Sites

General Forest Distribution of North-
western Indiana. . . . . . . . . .

Per Cent Contribution of Two Species Groups
to Stand Canopies . . . . . .

Contribution of Two Species Groups to Forest
Stands. . . . . .

Per Cent Sand, Silt, and Clay in Composite
Samples from the B Horizon . . .

Per Cent Sand, Silt, and Clay in Composite
Samples from a Depth of Four Feet. .

Position of Individual Soil Samples from the
B Horizon on Textural Triangle. . . .

Position of Individual Soil Samples from the
Four Foot Depth on Textural Triangle.

Surface Weather Map — August 29, 1969

Hypothesized Position of Lake Breeze Front
with Southwesterly Regional Wind . . . .

Directional Frequencies of Wind During 22 Lake
Breeze Days: 1000 EST . . . .

Directional Frequencies of Wind During 22 Lake
Breeze Days: 1300 EST . . . . .

vi

Page

18
21

32

43

A5

50

51

55

56
76

77

8O

81

Figure Page

17. Directional Frequencies of Wind During 22 Lake
Breeze Days: 1600 EST . . . . . . . 82

18. Per Cent of Michigan City Lake Breezes
Detected at Other Stations . . . . . . 87

19. Per Cent of Michigan City Lake Breezes
Detected at Other Stations on Days of
Southwesterly Regional Surface Flow . . . 89

20. Per Cent of Michigan City Lake Breezes
Detected at Other Stations on Days of
Westerly-Northwesterly Regional Surface
Flow. . . . . . . . . . . . . . 9O

21. Lake Breeze and Non—Lake Breeze Days at
Michigan City Plotted by Land—Water Tem—
perature Contrast and Mean Wind Speed:
Regional Flow from 180—3600 Inclusive . . 93

22. Lake Breeze and Non—Lake Breeze Days at
Michigan City Plotted by Land—Water Tem-
perature Contrast and Mean Wind Speed:
Regional Flow from 180—2690 Inclusive . . 9A

23. Lake Breeze and Non—Lake Breeze Days at
Michigan City Plotted by Land-Water Tem-
perature Contrast and Mean Wind Speed:
Regional Flow from 270—3600 Inclusive . . 95

2A. Lake Breeze and Non—Lake Breeze Days at
Ogden Dunes Plotted by Land—Water Tem-
perature Contrast and Mean Wind Speed:
Regional Flow from 180—3600 Inclusive . . 97

vii

CHAPTER I

INTRODUCTION

Recently an anomalous pattern in the spatial distri-
bution of average warm-season precipitation in northwestern
Indiana has been described by Changnon (1). This pattern,
the La Porte rainfall anomaly, consists of an island of
relatively high precipitation centered on the city of
La Porte, Indiana (Figure 1). During the period 1956-1960
the average summer (June — August) rainfall at La Porte
exceeded 17 inches; over the same period precipitation at
South Bend, twenty—five miles to the northeast, averaged
10 inches, while at Valparaiso, twenty miles to the south—
west, mean rainfall was approximately 13 inches. Similar
patterns of average annual number of thunderstorms and
hail days were also described. Changnon attributed these
patterns, which his data indicated have developed since
1925, to the addition of atmospheric pollutants by the
industrial complex near Gary, Indiana. There has been con-
siderable discussion as to whether the apparent precipita-
tion anomaly is real or is the result of measurement error
(2,3,4). For the purposes of the present study, the
greater rainfall at La Porte is assumed to be a real phe-

nomenon .

p 0-30.;

 

 

 

         

 
            
     

  

 

 

_ 200 30.30.2055 ”353

LI

Sunni-jinn... W.“

1
_
z .
_
L _
_
” 22.32;. _
__
_
.2 _
023...... 0 _
.2... £2; :5. _
. _
2.6.5.: _

(259%! 3::
[240.522

32-32 .<z<_oz_ 5.3331502

2. 20:52.35. S:o:<..mz:.. 23:2

 

 

 

 

 

Contrasting forest types along the Valparaiso moraine
in the vicinity Of the described rainfall anomaly, however,
suggest the long-term presence of an environmental gradient
predating heavy industrial air pollution. This moraine,
which approximately parallels the shore Of Lake Michigan,
extends almost through the center of the La Porte rainfall
anomaly as mapped by Changnon (Figure 2). The forests at
the eastern end of the Indiana portion of the moraine are
composed Of mesophytic species, predominantly beech (Eaggg

grandifolia) and sugar maple (Acer saccharum); those at the

 

 

western extremity are primarily black oak (Quercus velutina),

 

white oak (g. QARE): and hickory (gegye spp.). In the vici-
nity of Valparaiso, a sharp transition from one type to the
other occurs. Because beech in Indiana is an excellent in-
dicator of mesic conditions while the black oak normally
indicates a drier site (5,6), the forest contrast suggests
the possible presence of a moisture gradient due to either
climatic or edaphic factors. Analysis of the records from
the original U. S. land surveys has indicated that this
forest contrast existed at the time of European settlement
Of the area (7,8).

This study has three principal aims. The first of
these is to present the results of a forest survey designed
to describe the distribution of tree species within the
area of the Valparaiso moraine and hence confirm the exis-

tence of the contrasting forest types.

 

 

    

 

 

 
    

LOCATION OF THE
STUDY AREA
l
I
E
.fl'Fi‘PE'jl'i. _______
ILLINOIS . -
. lAKE
I MICHIGAN
I
o I
Argonne I l
. NM. Lab. i I \“ 1
. o | \“ .
A I Gary" I ‘ la Porte |
5 i me no. : !
: I Whom”! laI'III-Ie to. r’
I . o , I
I : ..._4
“unfit" mm on
i i
I l

   

ILLINOIS
INDIANA

[)0qu Hunt. scunnou

0

S

     

_____- __-_I

MICHIGAN ‘

I—._._l—O-I_I-I_O-l—I—\

INDIANA

0
South
Bend

VALPARAISO MORAINE
(Boundaries Approximate)

I0. ,,
Miles

_20

JO

I I
I»)
I

I

% JOE-5'74

 

FIGURE 2

 

Second, the results of a pilot survey of selected
subsoil characteristics along the moraine will be presented.
The purpose of this part of the investigation is to deter—
mine whether variations in the chosen parameters correlate
(spatially with the forest composition differences and there—
fore might be causally related to them. The absence of any
apparent soil—forest correlations would strengthen the sug-
gestion that some kind of climatic gradient is present.

The third aim is to develop a climatic hypothesis
which could help explain the long-term environmental gra—
dient suggested by the observed forest contrast and might
shed new light on the La Porte rainfall anomaly, and to
assess a research method designed to offer a preliminary
test of that hypothesis. The hypothesis is that the La
Porte anomaly results in part from spatial variation in the
degree of influence exerted upon the local climatology by
lake breeze flow from Lake Michigan. Specifically, it is
suggested that when the regional wind has a westerly com—
ponent, a situation which appears to be common in the area
during the summer months (9), interaction between the lake
breeze and the regional air flow produces a zone of con—
vergence which frequently coincides spatially with both
that portion of the Valparaiso moraine supporting a meso-
phytic forest and the La Porte anomaly. It is believed
that augmented vertical air motion within this convergence
zone can result in locally increased cloud formation and

precipitation.

A preliminary attempt will be made to evaluate the
hypothesis using data for wind direction and speed collected
at six sites in northwestern Indiana and northeastern
Illinois. It is believed that such data will permit detec—
tion of the presence of a lake breeze at each station. The
data were gathered during the months of June, July, and
August, 1969.

The influence of Lake Michigan and the other Great
Lakes upon regional and local climatology has long been a
subject of investigation. Most early studies focused on
the more obvious and easily detectable aspects of lake
modification and were primarily descriptive in nature. In
particular, lake—induced snowfall and moderation of tem—
peratures received considerable attention.

Brooks (10), in perhaps the earliest study of the
snowfall climatology of the region, discussed at length
the zones of higher snowfall in the Vicinity of the lakes.
Dole (11) described the regional pressure gradients which
seemed to favor lake snows. More recently, Thomas (12)
has reviewed the lake snow literature and the synoptic con-
ditions which are conducive to them, while Changnon (13)
has attempted to analyze and map the influence of southern
Lake Michigan upon snowfall.

The control exerted by the Lakes on local temperature
regimes has received considerable attention because of its
economic importance with regard to the location of fruit-

growing districts. Odell (1A) stated that higher winter

minimum temperatures on the lee side of Lake Michigan,
which reduce the likelihood of damage to fruit trees, are
a major reason for the success of orchards in the area.
Olmstead (15) reached a similar conclusion and noted that
the lake delays warming of the region in the spring, thus
apparently retarding blossoming until the danger of a se—
vere frost is lessened. Leighly (16) described and mapped
the impact of the Great Lakes on the annual march of tem—
peratures.

Lake modification of other climatic elements, in-
cluding cloudiness, frequency of fog, and humidity, has
been observed by Odell (1A) and Visher (17).

In recent years investigators have become increas-
ingly concerned with the dynamic interaction between the
Great Lakes and atmospheric processes that influence the
climate over adjacent areas. Particular attention has been
given to the warm—season lake breeze circulation.

Studies have shown that the arrival of a lake breeze
over an area usually brings a reduction in air temperature,
an increase in relative humidity, and supression of con—
vective activity and cumulus formation (18,19). The pro—
cesses which occur near the inland margin of a lake breeze
are quite different, however. Observational and theoreti-
cal studies Of sea breeze situations have revealed the pre—
sence of large vertical velocities resulting from conver—
gence with non-sea breeze air just ahead of these fronts

(20,21). Olsson (22) found similar strong upward motion in

convergence zones associated with lake breezes in western
Michigan. Under certain conditions, such lake breeze con—
vergence zones can produce bands of cumulus clouds and local
thunderstorms in the vicinity of southern Lake Michigan.
Lyons (23) Observed that towering cumuli can form parallel
to the Lake's southwestern shore during northwesterly geo—
strophic winds. Estoque (21), using a mathematical model

Of sea breeze conditions, found that vertical air movement
near a sea breeze front may be especially strong when the
geostrophic flow is parallel to the coast with low pressure
over the water. Since summer prevailing winds in northern
Indiana are southwesterly (9), it appears that the above
situation would be relatively common along Lake Michigan's
southeastern shore. Thus there is evidence that lake breeze
convergence can increase local precipitation and thunder—
storm activity and that such convergence could be an impor—
tant process in the Vicinity Of the La Porte rainfall
anomaly.

Relatively few vegetation studies concerned with
northwestern Indiana have been conducted and no known in—
vestigations of the forest contrast along the Valparaiso
moraine have been made. Shelford (2A) considered the area
to be ecotonal between beech—maple, maple—basswood, oak—
hickory forest types. Braun (25) described the area as a
tension zone between the beech—maple and oak—hickory forest

regions to the east and west of the study area, respectively,

and noted the absence of beech from extreme northwestern
Indiana. Cowles (26) concluded that the oak—hickory forests
on morainic uplands near Chicago would ultimately be re-
placed by the beech—maple association which he observed to
the north and east near Lake Michigan. However, Diller (27)
believed that soil moisture deficiencies in June, resulting
from higher temperatures and lower precipitation, restrict
the westward extension of beech and sugar maple in northern
Indiana. Potzger and Keller (7), using records of the ori-
ginal U. S. land surveys, mapped the occurrence of beech in
the presettlement forest cover of northwestern Indiana.
Their map indicates that the percentage of beech declined
abruptly from east to west in central Porter County within
the area of the Valparaiso moraine. Lindsey (28), also
working from land survey records, found a tongue of beech—
maple forest projecting into La Porte County from south—
western Michigan surrounded by oak-hickory and prairie
vegetation.

Few attempts have been made to relate vegetation pat—
terns to climatic modification by Lake Michigan. Quick (29)
and Kenoyer (30) observed that certain northern species
extend their ranges farther south in Michigan along the
Lake Michigan shore than they do farther inland. Potzger
and Keller (7) noted that the line of prevailing winds
crossing southern Lake Michigan seemed to correspond to

the occurrence of beech and other mesophytic species in

10

northwestern Indiana. Finally, Harman (31) examined forest
and climatic gradients resulting from lake modification
within the zone of sand dunes in southern Michigan and
Indiana.

The present study is an initial attempt at evaluation
of a possible spatial association between lake breeze flow,
the La Porte rainfall anomaly, and forest contrasts along
the Valparaiso moraine. It is hoped that it will contri—
bute to further understanding Of the climatology and plant

geography of the southern Lake Michigan region.

10.

11.

12.

CHAPTER I--REFERENCES

Changnon, S. A. 1968. The La Porte weather anomaly——
gact of fiction? Bull. Amer. Meteor. Soc. A9:
—11.

 

Ogden, T. L. 1969. The effect on rainfall of a large
steelworks. J. Appl. Meteor. 8: 585—91.

 

Holzman, B. G., and Thom, H. C. S. 1970. The La Porte
precipitation anomaly. Bull. Amer. Meteor. Soc.
51: 335-37.

Changnon, S. A. 1970. Reply (to Holzman and Thom,
1970). Bull. Amer. Meteor. Soc. 51: 337-A2.

 

 

Potzger, J. E. 1935. Topography and forest types in
a central Indiana region. Amer. Midl. Nat. 16:
212-29.

 

Potzger, J. E., and Friesner, R. C. 19A0. What is
climax in central Indiana? A five-mile quadrat
study. Butler Univ. Bot. Stud. A: 181—95.

 

Potzger, J. E., and Keller, C. 0. 1952. The beech line
in northwestern Indiana. Butler Univ. Bot. Stud.
10: 108—13.

 

Potzger, J. E., Potzger, M. E., and McCormick, J. 1957.
The forest primeval of Indiana as recorded in
the original U. S. land surveys and an evaluation
of previous interpretations of Indiana vegetation.
Butler Univ. Bot. Stud. 13: 95—111.

 

Visher, S. S. 19AA. Climate of Indiana. Bloomington:
Ind. Univ. Pubs., Science Series No. 13.

 

Brooks, C. F. 1915. The snowfall of the eastern United
States. Mon. Wea. Rev. A3: 2-11.

 

Dole, R. M. 1928. Snow squalls in the Lake Region.
Mon. Wea. Rev. 56: 512—13.

 

Thomas, M. K. 196A. A survey of Great Lakes snowfall.
Great Lakes Res. Div. Pub. 11: 29A-310.

 

11

13.

1A.

15.

16.

17.

18.

19.

20.

21.

22.

23.

2A.

25.

l2

Changnon, S. A. 1968. Precipitation from thunder—
storms and snowfall around southern Lake Michigan.
Proc. 11th Conf. Great Lakes Res. 285-97.

 

Odell, C. B. 1931. Influence of Lake Michigan on
east and west shore climates. Mon. Wea. Rev.
59: ADS—10.

 

Olmstead, C. W. 1956. American orchard and vineyard
regions. Econ. Geog, 32: 189-236.

 

Leighly, J. 19A1. Effects of the Great Lakes on the
annual march of air temperature in their vicinity.
Peps. Mich. Acad. Sci. Arts Letters 27: 377-A1A.

 

Visher, S. S. 19A3. Some climatic influences of the
Great Lakes, latitude, and mountains: an analy—
sis of climatic charts in "Climate and Man," 19A1.
Bull. Amer. Meteor. Soc. 2A: 205-10.

 

Munn, R. E., and Richards, T. L. 196A. The lake—
breeze: a survey of the literature and some
applications to the Great Lakes. Great Lakes
Res. Div. Pub. 11: 253—66.

 

 

Lyons, W. A., and Wilson, J. W. 1968. The Control of
Summertime Cumuli and Thunderstorms by Lake
Michigan during Non—Lake Breeze Conditions.
Satellite and Mesometeorology Research Project
Res. Pap. 7A. Chicago: Univ. of Chicago Press.

 

 

 

Wexler, R. 19A6. Theory and Observations of land and
sea breezes. Bull. Amer. Meteor. Soc. 27:
272—87.

Estoque, M. A. 1962. The sea breeze as a function of
the prevailing synoptic situation. J. Atmos. Sci.
19: 2AA-50.

 

Olsson, L. E. 1969. Lake Effects on Air Pollution
Dispersion. Ann Arbor: Univ. of Michigan, Dept.
Of Meteor. and Oceanography, Tech. Rept.

 

 

Lyons, W. A. 1966. Some effects of Lake Michigan upon
squall lines and summertime convection. Great
Lakes Res. Div. Pub. 15: 259—73.

 

Shelford, V. E. 1963. The Ecology of North America.
Urbana: Univ. of 111. Press.

 

Braun, E. L. 1950. Deciduous Forests of Eastern North
America. New York: Hafner.

 

26.

27.

28.

29.

30.

31.

13

Cowles, H. C. 1901. The physiographic ecology of
Chicago and vicinity; a study of the origin,
development, and classification of plant societies.
Bot. Gaz. 31: 73-108, 1A5-82.

Diller, O. D. 1935. The relation of temperature and
precipitation to the growth of beech in northern
Indiana. Ecology 16: 72-81.

Lindsey, A. A. 1961. Vegetation Of the drainage—
aeration classes of northern Indiana soils in

1830. Ecology A2: A32—36.

Quick, B. E. 1923. A comparative study of the distri—
bution of the climax association in southern
Michigan. Paps. Mich. Acad. Sci. Arts Letters
3: 211—AA.

 

Kenoyer, L. A. 1933. Forest distribution in southwest
Michigan as interpreted from the original survey.
Paps. Mich. Acad. Sci. Arts Letters 19: 107-11.

Harman, J. R. 1970. Forest types and climatic modifi—
cation along the southeast shoreline of Lake
Michigan. Annals Assoc. Amer. Geog. 60: In press.

CHAPTER II

METHODOLOGY

The study area for this project can be generally
identified as Lake, Porter, and La Porte Counties, the
three Indiana counties which border on Lake Michigan. It
is for these counties that the climatic hypothesis was
developed and evaluated. With regard to the forest and
soil surveys, however, the study area can be more narrowly
defined as that portion of the above counties which lies
within the Valparaiso morainic system (Figure 3). In the
field, published county soil survey maps were used to de—
limit the morainic area (1,2,3). These maps were completed
between 1918 and 19AA and therefore are highly generalized.
It was believed, however, that they would be adequate for
outlining the area of soils developed from glacial till.

In order to document the forest gradient, a field
' survey of forested tracts within the Valparaiso morainic
area was conducted during August and September of 1969.
Since the objective of the survey was to provide data on
forest composition and species distribution over a large
area rather than to permit complete phytosociological analy—

sis, the detailed sampling techniques commonly used in

1A

l5

 

n .532.

 

can

 

‘——z_4

toEocsum E2;
“3:50.; 3.3.2309
2:032 3.0.03.5

T
0:32.. 1
IIcmdiyltL. .

I I'I.|.n|.|.|.l

 

 

sIouIIII '

 

._
_
1
_.
1
1.
1
_
L
._
_

      

    

_ 2:: \ at»...
so.oc°>>o_ \\ o
w \\\I A...
1 \Il..-) ........... _
\\\u \\ _ .
. \
\\ . m \\\ _. _
:2: z \\ votiwxx\ . :3 n
‘ . c w »o
33...: O \ \\ v" “36‘“_ cacao notoOO _ 0 O _
\\ \\ u _
\ \ .
\\ \\ _
\\ _
\\\ Z<0_IU_E _
\ mx<4

<m¢< >n3hm uO m<2 ZO_._.<UO._

_ ..i .IIIMMEJ

 

 

 

 

16

ecological research were not followed. Instead, a simpler
design similar to that employed by Braun (A) and Whittaker
(5) was selected.

Within each stand selected for study two square one—
half acre plots were marked out. It was found that plots
of this size could be established and examined by the in—
vestigator without great difficulty. Plots were placed on
the most level portions of their respective woodlots at
least ten yards from any margin of the stand. Within each
plot all living woody stems three inches or more in diameter
were counted and recorded by species in order to obtain data
on present canopy composition. Cruising of several stands
revealed that analysis of two plots, giving a total sample
area of one acre, yielded a good estimate of stand composi—
tion. In addition, shrub species observed throughout the
stand were recorded, as were tree species noted in the stand
which did not occur within the study plots. Emphasis was
placed on tree species because they are less likely to be
influenced by minor degrees Of human disturbance than are
understory species (6). This method admittedly yields less
information than the more frequently used techniques, but
it allowed the investigator to survey a large number of
woodlots so that the distribution of certain taxa in the
study area could be mapped. Taxonomic nomenclature in this

investigation follows Gleason (7).

 

l7

Twenty—six stands were studied within the morainic
area (Figure A). This number was sufficient to allow an
analysis of the distribution of selected taxa. Stands
were selected for inclusion in the survey on the basis of
three criteria. The first of these was stand size; only
stands large enough to allow placing the plots ten yards
or more from all margins, thus avoiding "edge effect," were
included. The smallest woodlot studied was approximately
five acres in size. Second, only upland stands on generally
level sites were chosen; sites favoring excessive moisture
accumulation or depletion were avoided in an attempt to
eliminate topography as a variable factor. Locations of
stands surveyed are given in Appendix I.

The third criterion, degree of disturbance, was more
difficult to assess. All wooded tracts in the study area
have been disturbed by human activity to some extent.
Stands being considered for inclusion in the survey were
evaluated by inspection and in some cases through conver—
sation with the owners. Stands in which Old-growth trees
were few, or which had clearly been subjected to excessive
grazing or cutting, were not used in this study. The prob-
lem of disturbance in surveyed stands was anticipated, but
it was believed that the forest contrast being examined
would stand above any "noise" introduced by this factor.

From the data collected in the forest survey, absolute
and relative frequencies of species in the canopy were cal—

culated for each stand. For shrub species, presence lists

18

 

 

. =3:

 

 

 

2.0.... 30.0: tonesLam I

    

7.33;.«75301 2352.5 _ _ \ \\
.o faucaon 0.0....uoaa4III _ \ I \
I\
. FI\\\I
_ F . .
_ _
_ .
_ I
_ _
..I. I .l. \ ..
_ _ EX , .
. \ a
— _ \\\Io..°...t._l) _
A , \ an u\\\II_III/ IIIIIIIIIII
a L \ . xv _
. \ I \
. \\ a _ \\ _
\
. \ I_ \\ H
_ \ I .\ _
. \ \\ .00.
_ 0...t°4 . \ \ — _
H \\ n \
\ \
_ xx \x
\V -\
_\ \ 2.8.12.2
I \
PIIIKIII.II w¥<4

moz<hm hmmmOm ou>m>¢3m “.O ZOZ.<UO._

 

          

Ono—

 

 

 

19

were compiled. In addition, coefficients of similarity
as used by Morgan (8) and based on the number of tree
species in common were computed for all pairs of stands.

In addition to forest composition data, soil samples
were also collected at two locations in each forest stand.
All collection sites were on level upland areas within the
stands. At each site two samples were taken, one at the
depth of apparent maximum clay accumulation in the B hori—
zon and one immediately below a depth of four feet. Sam—
ples were gathered with a bucket—type soil auger and placed
in plastic bags for return to Michigan State University.
Samples taken at the four-foot depth were tested in the
field with dilute hydrocholoric acid for the presence of
carbonates.

At the University, all samples were analyzed to de—
termine their particle size distributions using the Bouyoucos
hydrometer method as described by Day (9), with the following
modifications. First, the sand fraction was determined by
weighing the material separated out by a sieve with a 7A
micron mesh. Second, the silt fraction was determined by
subtracting the combined percentages Of sand and clay from
100 per cent. Finally, the hydometer readings normally
taken at 270 minutes and 720 minutes were replaced by one
reading at A80 minutes. The Bouyoucos method has been
Shown to be sufficiently accurate and detailed for most

analyses of forest soils (10). Replication was carried out

20

for approximately one—tenth of the samples; since corre-
sponding results were in close agreement in these cases, no
further replication was performed. Soil texture was se—
lected for study because evidence indicates that it is an
important property in controlling the available moisture
within a soil, possibly the single most important such
property (11,12). In addition, pH was determined for each
sample using a Beckman meter.

Because the two soil samples at corresponding depths
in each stand were found in most cases to be similar in
their measured characteristics, they were combined to yield
an average stand value for each parameter. Simple correla—
tion coefficients were then calculated between each of these
parameters and the percentages of selected species or
groups of species in the stand canopy.

In order to evaluate the climatic hypothesis proposed
in this study, data regarding wind direction and speed for
the period June 11 through August 31, 1969, were collected
by a network Of six instrument stations in northwestern
Indiana and northeastern Illinois (Figure 5). The arrival
Of a lake breeze at a station is usually marked by a shift
in wind direction, a temperature decrease, and an increase
in relative humidity (13). Therefore measurements of these
parameters could be employed in an attempt to determine the
presence or absence of a lake breeze. Previous studies

(1A,15), however, have indicated that intense heating at

21

m ucaui

 

 

Ina

 

 

 

_

_

oz: :52 —
Q .

0.; 2.2.5.2... 4

 

 

I<p<2(;‘

3.0.03.0).

3:232; _
too
O

2.0%.... wwzao ZwOOO‘ ”

      
      

— — — —
u—‘---—p-—-._o—-—uHu—u—u-n_o—-—.—.—..

2<O_zu.£
wx(.

:5 23:32:.

mwtm thSDuhmz_ “.O ZO_._.<UO._

 

wzzoo: 4

 

 

22

the ground may modify the temperature and relative humidity
characteristics of lake air as it moves inland, making these
parameters less reliable as indicators of lake breeze flow.
For these reasons, data regarding wind direction and speed
were selected for analysis of lake breeze penetration in

the present project.

The instrument site at Westville, Indiana (Figure 5),
was established on a temporary basis by the Department of
Geography, Michigan State University. A Meteorological
Research, Incorporated, automatic weather station, with
sensors and recorders for wind direction, wind speed, and
temperature, was placed on the roof of the main building
at Purdue University's North Central Campus, approximately
forty feet above the ground. It was capable of operating
for thirty-one days without servicing and was in Operation
from June 11 to September 10, 1969.

The other five instrument sites (one in Illinois,
four in Indiana) are Operated by various institutions or
individuals as follows: Argonne, Illinois, by Argonne
National Laboratory; Ogden Dunes, by Mr. Robert A. Ward,

U. S. Weather Bureau cooperating observer; Michigan City,
by the Northern Indiana Public Service Company; Wanatah,
by the Pinney-Purdue Farm of Purdue University; and South
Bend, by the U. S. Weather Bureau. Instruments at these
sites are between twenty and forty feet above the ground.
Records from these stations were made available to the

investigator by the persons or agencies responsible for them.

 

23

In addition to differences in the heights of the in-
struments above the ground, there also was some variation
in the type of site. At Ogden Dunes the instrument tower
is located on a dune crest among trees only slightly shorter
than the tower, while the instrument at Westville was sub—
ject to updrafts and eddies caused by the building on which
it was situated. The other sites are in generally open
areas. This lack of uniformity in instrument situation is
recognized; because the study was concerned with the approx—
imate mean position of a boundary between contrasting wind
fields, however, it was believed that these differences
would not be important.

In keeping with the hypothesis stated in Chapter I,
wind analysis was limited to those days on which the
regional (non-lake breeze) air flow possessed a westerly
component. Those days were identified by examination of
data from the Argonne and South Bend stations. All days
during the period June 11 through August 31 on which the
wind direction at 0700 Eastern Standard Time was from 1800
to 360°, inclusive, were accepted initially. The U. S.
Weather Bureau's Daily Weather Maps (16) for the study
period were examined and days on which fronts passed through
northwestern Indiana or the immediate vicinity were elimi-
nated. This was done to avoid confusing wind shifts due

to frontal conditions with those due to lake breezes.

2A

Wind direction and speed data were then extracted
from the records of all stations for the remaining days.
Data were extracted for three times during each day: 1000,
1300, and 1600 EST. These times were selected on the basis
of earlier studies. Field investigations on the south-
western (lA) and eastern (17) shores of Lake Michigan first
detected lake breeze flow between 0930 and 1030. Thus
data for 1000 should represent the early stages Of lake
breeze development. Moroz and Hewson (17), working on the
Lake's eastern shore, reported that maximum lake breeze
penetration was attained sometime after 1500; Olsson (18),
in the same area, found that this stage was reached about
1830. Therefore data for 1600 should describe the lake
breeze near its maximum development. Data were also ex—
tracted for the intermediate time of 1300.

In the process of extracting these data, days for
which there was evidence of lake breeze development at the
Michigan City station were recorded. A shift of the wind
during the day which resulted in an increased northerly
component, followed later by a shift back to approximately
the early morning direction, was accepted as evidence of
lake breeze influence. These days were cross—checked
against data from Argonne to ensure that the shift was not
a regional event. Twenty—two such days were identified.
Collectively, these lake breeze days constituted the inten—

sive study period.

25

In order to graphically portray the frequency of lake
breezes throughout the study area, wind roses were pre—
pared. A wind rose indicates, for some locality, the pro-
portion of winds blowing from each major compass direction
over a specified period of time (19). Wind roses were
selected over the resultant wind technique because they
reveal the variability of the wind during the study period
and are perhaps more easily interpreted as well. They do
not incorporate the relative strengths of winds from various
directions; however, variations in wind speed with direction
were not expected to be marked in this study.

Tables were prepared indicating the number of days
on which the wind was blowing from each of sixteen compass
directions at 1000, at 1300, and at 1600 for each of the
six stations. Finally, a sixteen point wind rose was drawn
for each station and each hour (except for Ogden Dunes,
where wind direction was recorded using only eight points).
Placed on a map, the roses illustrate the spatial variation
of wind direction in northwestern Indiana on the identified

lake breeze days.

10.

11.

12.

CHAPTER II--REFERENCES

Bushnell, T. M. 1921. Soil Survey of Lake County,
Indiana. Washington: Gov. Printing Office.

 

Bushnell, T. M. 1918. Soil Survey Of Porter County,
Indiana. Washington: Gov. Printing Office.

 

Ulrich, H. P. and others. 19AA. Soil Survey: La
Porte County, Indiana. Washington: Gov. Printing
Office.

 

 

Braun, E. L. 1950. Deciduous Forests of Eastern
North America. New York: Hafner.

 

 

Whittaker, R. H. 1956. Vegetation of the Great Smoky
Mountains. Ecol. Monogr. 26: 1—80.

 

Spurr, S. H. 196A. Forest Ecology. New York: Ronald
Press.

 

Gleason, H. A. 1968. The New Britton and Brown Illus-
trated Flora of the Northeastern United States
and Adjacent Canada. New York: Hafner.

 

 

 

Morgan, M. D. 1969. Ecology of aspen in Gunnison
County, Colorado. Amer. Midl. Nat. 82: 2OA—28.

 

Day, P. R. 1965. Particle fractionation and
particle size analysis. In Black, C. A. (ed.),
Methods Of Soil Analysis (Madison, Wis.: Amer.
Soc. of Agronomy), Part I: 5A5—67.

 

Gessel, S. P., and Cole, C. W. 1958. Physical analy—
sis of forest soils. First North American Forest
Soils Conference, East Lansing, Michigan: A2—A8.

 

 

Lund, Z. F. 1959. Available water—holding capacity
of alluvial soils in Louisiana. Soil Sci. Soc.
Amer. Proc. 23: 1—3.

 

 

Petersen, G. W., Cunningham, R. L., and Matelski, R. P.
1968. Moisture characteristics of Pennsylvania
soils: I. Moisture retention as related to tex—
ture. Soil Sci. Soc. Amer. Proc. 32: 271—75.

 

26

1A.

15.

16.

17.

18.

19.

27

Munn, R. E., and Richards, T. L. 196A. The lake—
breeze: a survey of the literature and some appli-
cations to the Great Lakes. Great Lakes Res. Div.
Pep. 11: 253—66.

 

Lyons, W. A. 1966. Some effects of Lake Michigan upon
squall lines and summertime convection. Great
Lakes Res. Div. Pub. 15: 259—73.

 

Moroz, W. J. 1967. A lake breeze on the eastern shore
of Lake Michigan: observations and model.
J. Atmos. Sci. 2A: 337-55.

 

U. S. Weather Bureau. 1969. Daily Weather Map. All
dates from June 11 through August 31.

 

Moroz, W. J., and Hewson, E. W. 1966. The mesoscale
interaction Of a lake breeze and low level out—
flow from a thunderstorm. J. Appl. Meteor. 5:
1A8—55.

 

Olsson, L. E. 1969. Lake Effects on Air Pollution
Dispersion. Univ. of Michigan, Dept. of Meteor.
and Oceanography, Tech. Rept. Ann Arbor.

 

Conrad, V., and Pollak, L. W. 1950. Methods in
Climatology. Cambridge, Mass.: Harvard Univ.
Press.

 

 

CHAPTER III

THE PLANT GEOGRAPHY

Physical Setting

 

The study area for this project lies within the three
northwestern counties of Indiana which border on Lake Michi—
gan: Lake, Porter, and La Porte Counties (Figure 3). The
region is located between A1 degrees and A2 degrees north
latitude and between 86°30' and 87°30' west longitude.

The topographic features of northwestern Indiana are
the product of Pleistocene glaciation and associated fluvial
and lacustrine processes. The region was glaciated during
the Wisconsin glacial stage and consists of three physio—
graphic units (l). The Valparaiso Morainal Area, which is
the study area for the forest survey, extends through the
three counties from northeast to southwest approximately
five to ten miles inland from Lake Michigan. To the north,
.between the moraine and the Lake, lies the Calumet Lacustrine
Plain, and to the south the Kankakee Outwash and Lacustrine
Plain. In La Porte County, the morainic area consists of a
single belt averaging approximately eight miles in width;
westward from there it widens to twelve or thirteen miles

and loses its single—ridge character (2). In Lake County

28

 

29

and western Porter County, the northernmost portion of the
Valparaiso Morainal Area may actually represent the super—
imposed Tinley moraine (3) which is recognized as a dis—
tinct morainic unit in Illinois (A). According to Schneider
(3), however, there are no demonstrable textural or litho-
logical differences between Tinley and Valparaiso till in
Indiana. Drift thicknesses within the morainic area range
from less than 150 feet to more than 250 feet (2), with
perhaps 65 feet belonging to the Valparaiso moraine proper
(5).

Elevations in the morainic area range from approxi—
mately 650 feet to over 950 feet above sea level (6), thus
rising to a maximum of about 370 feet above the level of
Lake Michigan. Maximum elevations decline from northeast
to southwest. The Valparaiso moraine forms the divide be—
tween the Great Lakes and Mississippi River drainage systems.

Soils in the morainic area vary widely in texture
with the most prevalent types being the medium to moderately
fine textured members Of the Galena and Morley catenas (7,8,
9,10). In the western one—third of the area dark—colored
SOils developed under grassland vegetation occur inter—
SDGrsed with the lighter forest soils.

Northwestern Indiana has a temperate continental cli—
matxg designated Dfa according to the Koppen classification
(ll-). Summers are warm with a mean July temperature of

aPproximately 73oF; winters are cold, January having a mean

3O

temperature of about 25°F. The mean annual temperature is
approximately A9°F. Annual precipitation in the western
half of the study area averages 3A to 35 inches with about
20 inches falling during the warm season (April through
September) (12), while the 1931-1960 average at La Porte
was about 50 inches with 29 inches falling in the warm
season (13). Snowfall ranges from less than A0 inches in
Lake County to over 60 inches in northeastern La Porte
County (1A). The prevailing wind is from the southwest
during the summer and the northwest in the winter (12).
Local climate is the result of several interacting
controls. For the region which includes the study area,
two of these controls deserve particular attention (15).
Largely because of the barrier effect of the Rocky Mountain
system, westerly air flow at middle and upper tropospheric
levels over North America often assumes a wave pattern
which may remain nearly stationary for long periods of
time. The typical spacing of these waves results in a
mean upper level trough overlying the eastern United States;
this condition favors surface cyclogenesis and the advection
of air masses into the region. In addition, the absence
of major east—west topographic barriers in eastern North
America permits air masses advected from the Gulf of Mexico
and the Artic area to arrive in relatively unmodified con—
dition, thus further augmenting cyclogenesis. These factors

result in the highly variable climate of the eastern

31

United States. For further discussion of the climate of

the region see Trewartha (15) and Visher (12).

Review of the Literature

 

Northwestern Indiana is a region of transition be—
tween several vegetation types. Braun (16) described the
area as a tension zone between the beech—maple forest
region, which occupies most Of central and eastern Indiana
as well as southwestern Michigan, and the oak—hickory
region of Illinois and western Indiana. Shelford (17)
characterized the area as ecotonal between the beech—maple,
maple—basswood, and oak-hickory forest types. In addition,
prairie vegetation occurred in northern Indiana, notably
on the sandy soils of the Kankakee Outwash and Lacustrine
Plain (16,18). For a complete review of the literature
concerning the vegetation of the entire state of Indiana
see Petty and Jackson (19).

The most conspicuous feature of the plant geography
Of northwestern Indiana is a peninsula of mesophytic species,

particularly Fagus grandifolia (beech) and Acer saccharum

 

 

(sugar maple), which extends southwestward from Michigan
along the Valparaiso moraine. This projection is surrounded

on three sides by forests in which Quercus velutina (black

 

oak), Q. alba (white oak), and Q.nwcrocarpa (bur oak) pre—

 

dominate (Figure 6).
No known studies which specifically discuss the forest

contrast along the Valparaiso moraine have been made.

 

32

0

5.30:

 

 

 

 

 

On 0— n o

.uwozzzut
m2_(-O<§ On_(-<ma(>
50 >-(OZDO- u—(1_KO-t( I I I

‘—z_J

    

 
  

     

     

_ _ Ix
_ ” \\I\\I
H FI\\
_ \ U
H \ r
._ mm>hxthw_ On >¢O¥U_II¥<O
_ \ n
n A _
_I. I I. _ \ H
n . \ _
_ _ III\ I
. . \ o
. _ \ 13.33:...) .
..lh \\...71... \\ U IIIII
a _. \ _
. \ . _ \\ H
_ \ u \\ _
. \ . n
h .\ . . . H to
_ it: \ \ . \ \ _ _ e o
H . .\ ., \ .,
r. x 7 w , x _
4 xx, ms: snug . A
_ \ \ «243903. ... _
...Ix \ - z<o__..u:z
AIIRIIII :3

. <Z<.o2_ szhmmglhmOZ
“_O ZO_._.Dm_¢.—m_o hmm¢Om ._<~_me0

 

 

   

.053! 90:01 .25 Lemma; ”350m

 

Oh.—

 

 

 

 

 

33

Several investigations covering larger regions which in—
clude the morainic area have been conducted, however.
Cowles (20,21) observed that morainic hills in the vicinity

of Chicago supported forests of Quercus alba, Q. borealis

 

(red oak), Q. macrocarpa, and species of Carya (hickory),

 

while those both north and east of Chicago were occupied by
beech—maple forests. He believed that the beech-maple type
ultimately would develop in the Chicago area as well.
Shreve (22) placed northwestern Indiana in a grassland-
deciduous forest transition zone and stated that Quercus

macrocarpa, Q. velutina, and Q. alba were the most common

 

tree species. The change in forest composition on morainic
uplands between Indiana and Illinois was also noted by
Fuller (23); like Cowles, he considered the beech-maple
forest to the east to be the true regional climax on such
sites. Gordon (2A), having mapped Indiana vegetation by
reconnaissance survey, found a peninsula of beech—maple
forest projecting from northwestern La Porte County to the
Porter County boundary through an area otherwise supporting
oak—hickory forest. Braun (l6) mapped the boundary between
the beech—maple and oak—hickory forest regions as cutting
across the Valparaiso moraine near the midpoint of its
Indiana segment but indicated that the transitional nature
of the area made the placement of a boundary line quite
arbitrary. Kuchler's map (25) of potential natural vegeta—

tion indicated a peninsula of beech-maple forest projecting

3A

into La Porte County from Michigan and giving way on the
southwest to oak—hickory forest.

Studies by Potzger and others (26,27), based on analy-
ses of original land survey records, have suggested that the
peninsula of mesophytic species in northwestern Indiana
existed prior to major European settlement of the region.
Their investigation indicated an abrupt transition, near
the present location of Valparaiso, from forests dominated

by Fagus grandifolia and Acer saccharum on the east to those

 

 

in which Quercus velutina and Q. alba predominate. Rohr

 

and Potzger (28) found that the presettlement vegetation of
Lake County consisted of open oak—hickory forest inter-
mingled with areas of prairie. Lindsey and others (29,30),
working with the original survey notes and county soil maps,
attempted to correlate pre~settlement vegetation types with
major well drained soil types. Their results also indicated
a peninsula of beech—maple forest projecting southwestward
from Michigan along the Valparaiso moraine; however, they
concluded that this forest type extended only into north-
eastern La Porte County before being replaced by oak—hickory
forests. Meyer (31) also used survey records to map broad
categories of vegetation; the Valparaiso morainic area was
classified as supporting broadleaved forest.

Potzger and others (26,32) have found that EEEEE

ggandifolia is normally a sensitive indicator of mesic

 

conditions in Indiana while Quercus velutina is an excellent

 

35

indicator of dry site conditions. Rohr and Potzger (28)
have suggested that the westward replacement of Fagus

grandifolia and Acer saccharum by oaks and hickories in

 

 

northwestern Indiana indicates that some climatic or edaphic
factor is operating to produce drier site conditions toward
the west. They also reported, as did Finley and Potzger
(33), that microclimatic variations allow beech and sugar
maple to exist in only isolated stands west of the main
meSOphytic association and suggested that this further
implies a progressive habitat change from east to west.

The sequence of postglacial migration of forest
species into northern Indiana is not entirely clear. There
is general agreement that spruce-fir forests occupied the
newly deglaciated areas early and persisted until approxi-
mately 8000 years ago (3A,35,36). Working in southwestern
Michigan, Zumberge and Potzger (37) concluded that a pine
stage followed the spruce—fir period and lasted until 6000
years before the present. Then followed a period in which
oaks increased in importance, with an oak-hemlock—broadleaved
forest stage about A000 years ago and an oak—hickory maximum
(the xerothermic period) about 3500 years before the present.
This general scheme is supported by the findings of Guennel
(38) and Just (36). Potzger (39) reported that pollen
studies indicated beech invaded northern Indiana later than
it did Michigan, a difference Benninghoff (A0) attributed

to the blocking of migration from the south by an early

36

postglacial prairie peninsula. He concluded that beech
arrived in Michigan from the east and pointed out that this
species first appeared or attained a strong position in the
prairie peninsula region during the oak—hickory stage, a
fact which is not consistent with the interpretation of
that period as a dry xerothermic interval. Thus the beech
forests of northern Indiana are in places no more than 3000
years old, according to Benninghoff. Potzger and Freisner
(Al), on the other hand, believed that the area occupied
by beech has recently been decreasing.

Although agreement on details has not yet been at—
tained, it is clear that climate and vegetation patterns
in the north central states have undergone fluctuations
since deglaciation of the area. The possibility that
existing species distributions are not completely adjusted
to the present climatic conditions must therefore be con—

sidered.

Forest Composition

 

Twenty-six forest stands were examined in the study
area during August and September, 1969, to determine the
local distribution of forest types in the study area.
Twenty-five overstory species were identified in the sur-
veyed stands. No attempt was made to distinguish Age:

nigrum from A. saccharum because of the difficulty of

 

classifying intermediate forms. This procedure is not

Without precedent in ecological studies (A2) since the two

37

species have similar site requirements (A3). Also, Qggyg
ovalis was not separated from Qggyg'glabra. Harlow and
Harrar (AA) have indicated that such separation is generally
not made except by taxonomists because of similar morpho—
logical and ecological characteristics. In addition to

the canopy species, twenty shrub species were recorded.

For three of these, individuals large enough to be included
in the tree survey were encountered; therefore they were
recorded as both canopy and shrub species.

Table 1 indicates the per cent contribution of all
species to the canopy of each stand (values to the nearest
1%). The stands are numbered consecutively from northeast
to sOuthwest through the morainic area; therefore the table
also indicates the geographic distribution of the species
within that area. The first four species in the table,

Fagus grandifolia, Acer saccharum, Tilia americana (bass—

 

 

wood), and Liriodendron Tulipifera (tulip—tree), are im—

 

portant mesophytic species. These are followed by five
species which generally occur on drier sites: Qggyg gyggg
(shagbark hickory), Q. glabra (pignut hickory), Quercus
2192: Q. velutina, and Q. macrocarpa. The remaining species
are listed alphabetically. Table 2 indicates the occur—
rence of shrub species in the surveyed stands.

Examination of the first nine species presented in
Table 1 reveals an abrupt change in forest composition be—

tween stands 13 and 1A. East of that location (stands 1

 

j38

 

mm

OH

mm

OH

HH m

N

\0
Ln

wH w H
m: so me HH mm

NH 3 m Hm Hm

ON

OH
:m

NH

mm
Hm
MH

Hm
om

OH

OH

O

mm
OH
H:

OH
Hm

mm

.mm

Om

mm
mm

Hm

mH

m

OH
HH

LflONr-INr—Im

(\ILJWLON
:TN

HH

OH
mH
mm

HO
mm

O:
OH

HH

mH

Ln:

OH

mm

(\I

r—IMI—Im

OH

mm
Hm
m

Q'Nr-Ir-Ir-Im

[\

:H
O:
3

:H
OH
Hm

OH

 

when; mseHO

 

H OCNOHpoEm mSEHO

 

O EspHnHw mmnmmmmwm

 

mHHoonon msoposa

(\I

 

NCHPOHOm WSCSLL

m
H

 

H mcchHwnH> «Hupmo

 

mLch mcmezw

 

monocHo mcwszh

 

mCNOHLoEm w::menm
.QQm mswompmno

m mUHLoHH wzcnoo

 

 

mHHmscceHooo mHDHmc

H mHELOOHoLoo wzpmo

 

 

occhHHonmo mschan

m anoHHAc acfiefima
3 ESCHDDL L®O<

 

 

 

mmumoonome msoposa

 

Hm ochzHo> moonosa

 

OH mon msonosa

 

magmHm mmnmo

 

mpm>o mHawO

 

H whouHQHHJB coppcoooHLHH
O m

m :m mo

mm m: em

 

«CNOHLOEN mHHHB

 

Esnwcoomm Loo<

 

mHHomecmnm mommm

 

mm

mm 2N mm mm HN

ON

OH

OH

NH

OH

mH

:H

mH

NH

HH

OH

 

909832 ocmpm

mOHooom

 

.moHromO ocmpm Op *wOHooom cone

HHd Mo mCOHuanhucoo pcmo hmmII.H mdm<e

.aouoEmHU :H monocH m can» mmoH mEOpm Hwooz mcH>Hq*

 

39

>4

.qam chH>

 

x x x ommucoa EscpspH>

 

x x EzHHOOHLOom Escpan>

x EHHocHAs mmHmzmmsm

x mHHouHUCSDOL waHEm

x mHmcmvmcwo msospEmm

x x x x x x x x .oaw mmmmm
x x HomeOCHO moon

x mumme maze
x mcchHmnH> macsnm

x x x x x x x x x x x x x .Qam.m:mmHoocozppmm
x mcumwp mHHonosz

x x x x x x x x x x x x x :Honcoo «LOOCHH

x x mcchprH> mHHOEmEme

 

 

 

 

 

 

 

 

 

 

x x X x x x x x N x x x .Qam wsmmmwmho

 

x x x mCNOHnoEm msHHpoo

 

x x x x x mmoEoomn mchoo

 

x x x mUHLOHO mchoo
x x x mHHomHCLOOHm mscnoo

x x x x x x x x mQOHHLp MCHEHw<

 

 

 

ON OH OH NH OH OH :H OH NH HH OH O O N O m z m N H

 

amassz ccmpm mOHomam

 

.mUCMpm cozo>nsm CH *moHooqm nongm Ho ooconhzooOII.N mqm<e

A0

through 13), the four selected mesophytic species accounted
for A5% or more of the canopy in all but three stands. To
the west (stands 1A through 26) these species were infre-
quently encountered, with the five oaks and hickories con—
tributing A9% or more of the canopy in each stand.

These data suggest the presence of two distinct forest
types represented by stands 1 through 13 and 1A through 26,
respectively. The remaining sixteen species in Table 1
offer further evidence to support this suggestion. Asimina

triloba (papaw), Carpinus caroliniana (blue beech), Ostrya

 

virginiana (ironwood), and the two elms, Ulmus americana

 

 

and Q. rubra, were essentially restricted to the mesic

eastern part of the study area; the hawthorns, Crataegus

 

spp., were found primarily in the western stands dominated

by oak and hickory. Prunus serotina (black cherry) and

 

Quercus borealis (red oak), on the other hand, were more

 

nearly ubiquitous.

Fagus grandifolia appears to be the best indicator

 

species for the mesic forest type, since it occurred in
all thirteen eastern stands and was restricted to them.

Quercus velutina is perhaps the best indicator of the more

 

xeric oak and hickory stands; it was found in all thirteen
western stands and was absent from all but two of those
containing beech. These findings are in agreement with
the conclusions reached by Potzger and others (26,32)

regarding the best arboreal indicators of mesic and drier

Al

site conditions in Indiana. Because Acer saccharum was

 

associated with beech in all but one of the mesophytic
stands, the forest cover of the eastern part of the study
area is considered to be a beech—maple type. The forest
type represented by the thirteen western stands is desig—
nated oak—hickory.

From Table 2 it is evident that the distributions of
a number of shrub species reflect the change in canopy com-

position. Asimina triloba, Cornus alternifolia, Lindera

 

benzoin, and other less common species were found almost

exclusively in beech-maple stands, while Cornus racemosa,

 

Corylus americana, Prunus virginiana, and Vibernum Lentagp

 

were nearly restricted to oak-hickory stands.

In order to further indicate the degree Of composi—
tional contrast between the two forest types, coefficients
of similarity (A5) were computed for all pairs of stands.
The coefficient is based on the number Of canopy species
two stands have in common and ranges in value from 0 (no
common species) to 100 (species composition identical).

The coefficients for all pairs involving only the thirteen
beech—maple stands were averaged to yield a mean coeffi-
<fl_ent for that forest type. The same procedure was followed
for the oak—hickory stands. Finally, the coefficients for
all pairs of stands of contrasting forest type were averaged.
Table 3 presents the results. This coefficient probably

underestimates compositional differences because it gives

A2

no weight to the importance of each species in terms of

its relative density or its contribution to the total basal
area of the stand. Nevertheless the mean coefficient of
similarity between differing stand types is markedly less
than the means between stands of the same type.

TABLE 3.——Mean Coefficients of Similarity Between Beech—
maple, Oak—hickory, and Contrasting Stands.

 

 

Stands Mean Coefficient
Beech—maple stands 63.0
Oak—hickory stands 63.5
Contrasting stands 29.5

 

In Figure 7 the contributions (in per cent) to each
stand of two groups of species have been graphed against
approximate stand location along a northeast—southwest
transect within the Valparaiso morainic area from the
Michigan state line to the Illinois border. The two groups
of species are (l) the four mesophytic species presented

first in Table l (Fagus grandifolia, Acer saccharum, Tilia

 

 

americana, Liriodendron Tulipifera) and (2) the hickories

 

 

and oaks which followed the above species in that table

(Carya ovata, Q. glabra, Quercus alba, Q. velutina, Q.

 

 

macrocarpa). The graph illustrates the basic segregation

 

of the two species groups and the abrupt shifting of pre-

dominance from one to the other.

A3

4 MESOPHYTIC SPECIES

------ 5 OAKS AND HICKORIES
(SEE TEXT FOR ACTUAL SPECIES)

 

 

 

 

loo-AI»
x I
II III
II \I II
I \ /A\1 {I
I I f I I I
I I / I , I
I \ / I I
3°" A I \ / I I I
/ \ I I
f" \ I I/ I I I
I \ I I I I
«r I \ I \ f I
l \' I I I
,’ ‘1' I I II
I
J I [I I
60" I l I
I I |
I I I
II I
.. y I I
I I
I {I
404} l I “
I I
I II
I I
I I I
4- I I
I I I
, I
I I
20.». I I‘
I
I l I
I I
I. I / I
I I I
I A I I
l/ \\ I |
A A 1 n 1 1 4 A V L J\:\L 1/’I‘1.L_L. J l 1 I L
25 20 IS IO 5 I
STAND NUMBER
sw.¢__-._-_--_,_- .. .1.-- .——— H >NE

FIGURE 7
PER CENT CONTRIBUTION OF TWO SPECIES GROUPS TO

STAND CANOPIES

 

MU

Figure 8 indicates the spatial distribution of the
forest types. Stands have been classified into three groups,
each represented by a different symbol: (1) those in which
the four mesophytic species contributed 60% or more of the
canOpy stems; (2) those in which the five oak and hickory
species accounted for 60% or more of the stems; and (3)
those in which neither group predominated. It is apparent
that the transition from one forest type to the other lay
in the vicinity of the city of Valparaiso.

Table H presents two additional measures of compari-
son between the beech—maple and the oak—hickory stands. The
average number of trees per acre was greater in the thirteen
meSOphytic stands of the eastern part of the study area. In
addition, the total number of species observed (including
both tree and shrub species) was greater for the beech—
maple stands than for those dominated by oaks and hickories.
Similar contrasts in density and compositional diversity
were observed by Harman (U6) between dune forests in southern

Michigan and in Indiana.

 

 

TABLE U.--Two Measures of Comparison Between Forest Types.
Forest Type Trees/acre Number of species
Beech—maple 14M 38

Oak-hickory 96 28

 

 

45

 

 

$00 ‘30u0 .2332 3:3 “02(pn 0
«2.080.: 02¢ u8<O n #0. «62¢: D
“20-;u 0.;850nui v *0. 2.21..“ O

_luozzvfivn. .2.(-OI Ou.<-<La<>
‘0 >u<°230¢ uu(5.xO-ts( III

   
        

  

_
\\—
\
H I\\I\ .
VIIII _
n unn- —
van— o~O .
Zn 2 n _
_
I. I I _ .
n \O D_ _
_ _ III\: .. a. _
U \\ o to _ .
_ — \ o—Aw..m.ot.l> _
u H \ n. u Dn.\\uII_III/ IIIIIII .
.... \\fi __om:2c.\ III.—
_I \\ .o. \\ _ _
_ \ so _ \\\ _ .
O. \ _
_ \\ .o L\\ _ _
\ \. b. .
_ ...:3 o \ \ \ \ _ _ no. _
\\ no \\ m
_- I. \ O\\ .
\ v\
\ \ _
\ .
_ \\fi n0\\ _
_\ \ z<o_:u_2 _

m¥<4

may—(hm ...mmflOm Oh mmaOaO mum—Una; Os?— mO 203395.200

 

on.—

 

 

U6

Since studies by Potzger and others (26,27) have sug—
gested that the distribution of forest types at the time of
the U. S. land surveys (about 1800—1830) was similar to
that described here, it appears that the forest contrast is
the result of an environmental gradient and has not been
produced by varying land—use practices.

The possible ecological importance of fire in the
study area should also be considered. Fires apparently
were frequent in the prairie areas of the central United
States prior to EurOpean settlement (18). Ward (U7),
working in Wisconsin, concluded that fires were important
in controlling the western limits of several meSOphytic

tree species, including Acer saccharum. He suggested that

 

the abrupt rather than gradual elimination of these species

to the west and their replacement by Quercus macrocarpa

 

was the result of more frequent burning. Thus the possible
role of fires from nearby prairie areas in influencing
species distribution within the study area should not be
overlooked. A critical evaluation of the probable impor—
tance of fires is beyond the scope of this project. It

can be pointed out, however, that no evidence has been
found suggesting invasion of one forest type by the other
since the original surveys. It seems likely that regional
differences in the frequency of fires have been eliminated
since EurOpean settlement. No evidence of recent burning

was observed in the stands surveyed. These considerations

H7

seem to suggest that fires did not play a major role in

establishing the forest gradient.

Soil Patterns

 

The predominant forest soil of Lake County is the
Morley silt loam (7,“8). This soil has developed on a
silty clay loam parent material and is leached to a depth
of less than 40 inches. In La Porte County Galena silt
loam is the most extensive upland soil (9); it is generally
similar to Morley in texture but is more deeply leached.
This soil is most widespread northeast of the city of La
Porte; in the western part of the county, coarser soils,
including the Hillsdale and Chelsea series, are inter—
spersed with it. Soils of the moraine in Porter County
appear to be primarily of the Morley and Galena series
(8,10), although there is some uncertainty due to the lack

of a modern soils map. According to Soils of the North

 

Central Region of the United States (U9), the portion of

 

the moraine west of Valparaiso is characterized by rela—
tively fine textured soils. From Valparaiso east to La
Porte medium textured soils occur, while northeast of La
Porte coarser soils predominate. At the northeastern end
.of the Indiana portion of the moraine a small area of finer
textured soils similar to those in Lake County projects
southward from Michigan. This general pattern is supported
by the findings of Krumbein (5): he observed that the
Valparaiso till is clayey west of Valparaiso and northeast

of La Porte, but is considerably more sandy between.

A8

Textural analyses were made of soil samples from each
stand in order to identify any pattern of soil texture
which might agree with the distribution of forest types.
Two samples were taken in each stand and their analysis
results averaged. Table 5 presents the average percentages
of sand, silt, and clay for each stand. The values for
individual samples are given in Appendix III.

In Figure 9 average percentages of sand, silt, and
clay in the B horizon are graphed according to stand loca—
tion, and Figure 10 is similar but represents the texture
at a depth of four feet. In both diagrams, a general de—
crease in the sand percentage from east to west is apparent.
There is also a trend toward higher clay percentages in
the same direction, although this is less conspicuous at
the four—foot depth than in the B horizon. The silt frac—
tion of the B horizon displays no clear trend along the
transect; there appears to be a slight tendency toward
higher silt content to the west at a depth of four feet,
however. Thus a gradient of soil texture within the
Valparaiso morainic area is suggested.

Table 6 presents simple correlation coefficients be—
tween five species or groups of species and the percentages
of sand, silt, and clay at the two depths graphed in
Figures 9 and 10 (in the horizon of maximum clay enrichment
and at four feet). The four mesophytic species and the

oak—hickory group are the same as used in Figure 7. For

“9

TABLE 5.-—Average Percentages of Sand, Silt, and Clay in
Soil Samples from Surveyed Forest Stands.

 

B Horizon

 

Four-Foot Depth

 

 

Stand NO' Sand Silt Clay Sand Silt Clay
1 22.6 43.4 34.0 41.9 34.8 23.2
2 51.8 32.2 16.0 43.6 36.4 20.0
3 79.2 17.8 3.1 94.2 3.0 2.8
4 43.7 30.6 25.6 47.2 23.9 28.9
5 40.2 40.8 18.7 42.4 31.4 26.2
6 11.2 52.8 36.0 20.7 49.8 29.5
7 23.4 45.2 31.3 1 .5 48.5 33.0
8 26.4 47.2 26.4 51.3 25.2 23.6

. 9 20.5 49.0 30.5 17.3 46.4 36.2
10 27.2 39.2 33.6 35.0 37.8 27.1
11 51.3 25.2 23.5 26.5 43.9 29.6
12 28.3 44.0 27.7 22.6 42.0 35.3
13 34.7 38.2 27.1 35.8 39.6 24.6
14 20.8 48.0 31.2 26.0 47.0 27.0
15 16.2 50.4 33.3 14.4 52.7 33.0
16 17.8 47.8 34.4 20.6 53.4 26.0
17 25.4 41.4 33.2 29.8 41.0 29.2
18 16.6 41.4 41.9 26.2 46.2 27.6
19 39.0 36.6 24.4 57.6 24.6 17.8
20 11.2 48.5 40.4 14.6 57.7 27.8
21 21.0 38.8 40.2 16.0 51.0 33.0
22 15.2 41.2 43.6 38.0 35.7 26.3
23 2.2 47.4 50.4 4.0 61.8 34.2
24 13.0 36.9 50.1 13.6 46.0 40.5
25 4.0 34.6 61.4 13.2 46.4 40.4
26 24.5 35.9 39.6 22.9 44.0 33.2

 

 

5()

 

 

 

IOOII
—'-—-—SAND
————— .-su1
' CLAY
80*-
I
/\
I
I- I I
I I
I I
’ I
60" A II I
I I
I
I- K '/'R-\ I I
i'\ . '\ / \ I‘ ./ \vw’I ‘ I I
I‘ \. .’ \ -’ \ A I ‘ I ' ‘ I
AOP / \ / _./ \ /' \.’ I '
\ V I/ . I
J I II I. I \. I/
o—J/ \ [\ I I \ /I
I \ II A\ I I I I J I
\ .
~ I / I, J I/‘\ I I /
\I J/ l J \ \ /'
I I I r’ \’ /\ ’ \ I' ‘
I /‘I I I / '1 \ ’ \I I \/ I
70" I I I I/ \ I V
I I I I v I I
\ I I I \I
I I I K I \
I I I ’\ I
- I I I I \ l
/ \ /
\I I/ \v/
I I .
25 1 1 l 210 1 L 1 1 I15 4 1 L J ‘10 L 1 1 1 g 1 1 1 ‘1
STAND NUMBER
SW? ¢NE
FIGURE 9

PER CENT SAND, SILT, AND CLAY IN
COMPOSITE SAMPLES FROM THE B HORIZION

5].

—--——— SAND

CLAY

.
'0’
.
l.
l..-
l'.’.
'u'o'
u'.

 

 

low/T

800

'9'-
\n“.
n, .‘u
/ I
/ \
,I‘.\.
‘u\.\. III
1.‘ I)
I. /
«I. IV
,nI.I. III III‘I‘III-‘I
‘|II|I‘“"‘.’-I
l’!’ a‘
-\.‘|\n """I
A.‘ \x
. \\
I.., \\
.V A“
\ l
I\ /
A I)
I /
/ \\
. \
\
V .A
\. //
.\. I/
\ /
/,
.\ I,
x V
\
. \
r \
.I \
I.’. \
\.V A
.\. .Y
xi IIIIII
II‘I‘I'Ir.’
IIIE.‘ .’
III“ .l.’
t!’ .‘
I’ll o‘n‘o
"' u‘ ‘
‘.|‘4'E‘r"
‘.‘o "
.lI.‘uI‘ """
/. \\\
I I \\
.l. \\\
.Ԥo "
.‘I‘.‘\.\ ' It'll,"
.‘.I\ I'll
\.I I.\ Iluo
l.’.,. \\
,.I.I.I \
r I»
I \\\
I ‘\
¢ 0 I
o O o
.0 4 2

10

IS

20

25

STAND NUMBER

#NE

 

SW—s

FIGURE 10

PER CENT SAND, SILT, AND CLAY IN COMPOSITE

SAMPLES FROM A DEPTH OF FOUR FEET

52

.3m>m3 mo. pm p23033flcmflm @333>*

 

 

 

 

 

 

 

 

*Nmm. 30m. *333. *m33.n wm3.u *om3. mod. *mmm.u mmfiomgm mwpmo
Gem m30pmza m>fim
Hom.u owe. woo.u mmo. 3303. $333. moo.u m3o.u mcfipsam> agopmsa
*Hmm.a m3m.u *mmm.u *3mm. m3o. *3m3.- mm3.: *mwm. Apxmp mmmv wmflomgm
OHpmflmommE Lzom
3mm.n o3m.: *om3.u *om3. mma.u *mwm.u mm3.- *3m3. ssmmgoomm pmo3 I
Ucm mHH0%HUcme .m
*NH©.- 3mm.- *mm©.- *w3w. mmm. m33.- mmm.- 30mm. «330%anmam msmmm
mg 3330 333m wcmm mg 3m30 333m UQQm
gummm poomlhsom QONHhom m mmfiomam

 

.moflpmflmmpowpmgo aflom ucw mmflomam mmhe cmmSpmm mQOflpmHmppooll.o mqm<9

\

53

these correlations, two modifications were made in the
original data. First, stand 3 was omitted because it was
located on extremely sandy soil which occurs in a narrow
belt along the northern margin of the moraine. Second, one
of the two soil samples in stand 19 was excluded because
examination of the Porter County soil map suggested that it
represented an isolated sandy pocket. Soil fraction values
for the other sample were used instead of the two—sample
average for that stand. Correlation coefficients were
tested for significance using the F test described by
Blalock (50)~

In general, the mesophytic species and groupings had
positive correlations with the percentage of sand in the
soil and negative correlations with per cent silt and per
cent clay. The correlations with sand at both depths, with
silt at four feet, and with clay in the B horizon (except

for Fagus grandifolia alone) were significant at the .05

 

level. The more xeric oak and hickory species, on the
other hand, correlated negatively with sand and positively

with silt and clay. Quercus velutina alone did not follow

 

the trend of the larger group exactly, but did show posi—
tive correlations with per cent clay at both depths.

It appears that the soils of the western part of the
Valparaiso morainic area, which support an oak—hickory
forest type, tend to be higher in clay and silt content
and lower in sand than those to the east on which beech—

maple forest occurs. This relationship is further

54

illustrated by Figures ll and 12. In these figures, all
individual soil samples were plotted on textural triangles
using different symbols for those samples taken in beech—
maple stands (stands l—l3) and those from oak—hickory
stands (stands lU—26). Figure ll displays the B horizon
samples; Figure 12 represents the samples from a depth of
four feet. Both diagrams indicate a tendency for higher
clay content under the oak-hickory stands, particularly

in the B horizon. Clay and silty clay textures were common

 

at that depth in the western oak—hickory stands, while loams
and clay loams were abundant in the beech-maple stands.

The trend toward decreasing sand content westward is pro—
nounced at both depths. Little variation in the amount of
silt can be detected in the B horizon; however, larger silt
percentages to the west do seem indicated at the four-foot
depth.

Hydrochloric acid was used to check for the presence
of carbonates at the four-foot depth. In eleven of the
thirteen beech-maple stands carbonates were absent in both
soil samples. Carbonates were detected in one of the two
samples from each of the two remaining stands. On the
other hand, carbonates were present in both samples from
eight of the thirteen oak—hickory stands and were detected
in one sample from each of the other five stands. Thus the
depth of leaching appears to decrease from east to west

along the moraine.

 

 

55

   

 

CLAY \
‘ 40 ’0
‘ / 6%
//
- o
\- m
/ ¢
A
/ A\ A
/ \ m
- r
0; sum \\ "
/ ‘ A CLAY \
_________‘___L_L‘A.__‘_ _____ v50 \
A . ‘ \
\ ° .: \
A ‘ ‘ \
CLAY LOAM . . . 0‘ sum .\
..0 . CLAY ‘{
. .0 . LOAM \\
>——L———‘v ————————————————
. // O
A \
° / ‘\ so
/ f
LGAM o / \
/ \\
/ SILT [DAM ,__.____\
/ /
/ /
\______// /
/
/ / SILT
/
._ -- _ ,,_.__-__... -\*--~- T_ \ { 3 100
80 60 40 20
<— PER CENT SAND +—-
O BEECH-MAPLE STANDS ‘ OAK-HICKORY STANDS
FIGURE 1]

POSITION 0F INDIVIDUAL SOIL SAMPLES FROM THE B HORIZION 0N
TEXTURAL TRIANGLE

56

 

 

 

 

IOO
\
\
<\
\
20
so
\\
.\
(W‘ \
CLAY \
~ 40 .36
,X a»
/ Q.
. 7;
01"
I
smv G-
CLAY
_______________ _A_.‘__.____. 60 \
A
CLAY LOAM A.‘snnv ~
_._°;__:___‘_‘.___ $955.1-“
0 A
o /
/
lOAM /
/
/ sun LOAM
/
L 4/
/ /
/ /
/ /
j ‘ V V
40 20
‘— PER CENT SAND 3__
O BEECH-MAPLE STANDS A OAK-HICKORY STANDS
HOURS}?

POSITION OF INDIVIDUAL SOIL SAMPLES FROM THE
FOUR-FOOT DEPTH ON TEXTURAI. TRIANGLE

 

57

Table 6 (p. 52) also indicates the degree of correla—
tion between species groups and soil pH values. Several
significant correlations were obtained at the four—foot
depth, however, these probably reflect the variation in
leaching depth between stands of the two forest types. All
correlations with B horizon pH values are small and only

one, that for Quercus velutina, is significant at the .05

 

level. Values of pH for all samples are given in Appendix IV.
Evaluating the significance of the forest type—soil
texture relationship suggested in this study is difficult.
The available water capacity (AWC) of a soil is most fre—
quently defined as the amount of moisture held in the soil
at tensions between .33 and 15 atmospheres. Several studies,
assuming these limits, have found significant positive cor—
relations between the silt content of a soil and its AWC
(51,52,53). Based on these reports, it might be expected
that the soils of the western part of the study area, being
higher in silt content, would have greater AWC than those
to the east. It has also often been reported that higher
AWC is attained in clay loams and clays than in loams or
sandy loams (5M,55), a fact which would again suggest that
more favorable soil moisture characteristics would be found
in the western portion of the study area. Franzmeier and
others (56), however, have concluded that .06 and 6.0 at—
mospheres more adequately delimit the range of tensions at

which soil water is readily available to plants. Using

58

these limits, they found that loamy sands, sandy loams, and
loams generally exceed clay loams and clays in readily
available water capacity (RAWC). Franzmeier's study sug—
gests that the coarser soils east of Valparaiso may have
higher RAWC's than those to the west.

Northwestern Indiana is a tension zone between the
beech—maple and oak-hickory forest regions (16). In such
transitional areas, variations in site characteristics
determine which vegetation type prevails in a given loca—
tion. It seems very possible that, under these conditions,
the higher clay content of the soils in the western part
of the study area could reduce the readily available water
capacity sufficiently to affect the vegetation type.

Beech, in particular, has been found to be sensitive to
reduced soil moisture conditions (57). The location of
the boundary between medium textured and finer textured

soils, as mapped in Soils of the North Central Region of

 

the United States (U9), corresponds closely to the transi—

 

tion between the two important forest types in the study
area. On the basis of the results of the soil texture sur—
vey, it is tentatively concluded that the forest contrast
cannot be cited as strong evidence for a long—term La Porte
rainfall anomaly which might be associated with lake breeze
convergence.

The forest contrast may be the result of a complex

of interacting factors. Winter snowfall is considerably

59

heavier in La Porte County than in the western part of the
study area (1U,58) and this could affect soil moisture con—
ditions during the early part of the growing season. In
addition, the study area lies near the margin of the "prairie
peninsula" (18) within which precipitation—evaporation
ratios decrease, precipitation becomes more variable from
year to year, and summer drought is a frequent occurrence
(59,60). It is possible that these climatic characteristics
become more pronounced westward in northern Indiana. These
factors, as well as soil textural differences and a long—
term warm—season precipitation gradient associated with

lake breeze convergence, could collectively be responsible
for the forest contrast.

The differences in depth of leaching between the
eastern and western parts of the morainic area could result
from one or more of at least three possible causes: (I)
textural variations; (2) differences in the amount of limey
material originally present in the till; or (3) variations
in the amount of precipitation. The soils of the western
part of the study area are fine textured; subsoils occa—
sionally fall into the clay textural class and percolation
through them is often severely limited (7). These factors
could have resulted in less leaching than in the coarser
soils to the east. Krumbein (5) found that the average
contribution of limestone to the gravel fraction of three

samples taken west of Valparaiso was 10.2%, while for three

 

60

samples taken east of that city the mean was 3.3%. This
suggests that the lime content of the western parent mate-
rials may have been greater than in those to the east.
Finally, if the La Porte rainfall anomaly has been a long—
term phenomenon, the higher precipitation could have pro—
duced greater leaching in that Vicinity. Assessing the
relative importance of each of these factors is beyond the

scope of this study.

10.

11.

CHAPTER III——REFERENCES

Wayne, W. J., and Zumberge, J. H. 1965. Pleistocene
geology of Indiana and Michigan. In Wright, H. E.,
and Frey, D. G. (eds.), The Quaternary of the
United States (Princeton, N. J.: Princeton Univ.
Press): 63—83.

 

 

Wayne, W. J. 1956. Thickness of Drift and Bedrock
Physiography of Indiana North of the Wisconsin

 

 

 

Glacial Boundary. Bloomington, Ind.: Ind. Dept.
of Conservation, Geol. Survey, Rept. of Progress
No. 7.

Schneider, A. F. 1967. The Tinley moraine in Indiana.
Proc. Ind. Acad. Sci. 77: 271—78.

 

Bretz, J. H. 1955. Geology of the Chicago region.
Part II——the Pleistocene. Ill. St. Geol. Survey
Bull. 65, Part II.

 

Krumbein, W. C. 1933. Textural and lithological vari—
ations in glacial till. Jour. Geol. 41: 382-408.

 

Schneider, A. F. 1966. Physiography. In Lindsey, A. A.
(ed.), Natural Features of Indiana (Indianapolis:
Ind. Acad. Sci.): U0—56.

 

Wenner, K., and Persinger, I. 1967. Lake County
Interim Soil Survey Report. Unpublished.

 

 

Bushnell, T. M. 1918. Soil Survey of Porter County,
Indiana. Washington: Gov. Printing Office.

 

Ulrich, H. P., and others. 19““. Soil Survey: La
Porte County, Indiana. Washington: Gov. Printing
Office.

 

 

Correlation Legends for Porter and La Porte County Soil
Survey Reports. Personal communication from Mr.
Frank W. Sander, Soil Conservation Service,
Indianapolis. November 18, 1969.

Trewartha, G. T. 1968. An Introduction to Climate.
New York: McGraw—Hill.

 

61

12.

13.

l“.

15.

16.

l7.

l8.

19.

20.

21.

22.

23.

2A.

26.

62

Visher, S. S. 194“. Climate of Indiana. Bloomington,
Ind.: Ind. Univ. Pubs., Science Series No. 13.

 

U. S. Weather Bureau. 1968. Climatological Data-
Annual Summary, Vol. 7H.

 

 

Schaal, L. A. 1966. Climate. In Lindsey, A. A. (ed.),
Natural Features of Indiana (Indianapolis, Ind.:
Ind. Acad. Sci.): 156370.

 

Trewartha, G. T. 1961. The Earth's Problem Climates.
Madison, Wis.: Univ. of Wis. Press.

 

Braun, E. L. 1950. Deciduous Forests of Eastern North
America. New York: Hafner.

 

Shelford, V. E. 1963. The Ecology of North America.
Urbana: Univ. of 111. Press.

 

Transeau, E. N. 1935. The prairie peninsula. Ecology
16: A23-37.

Petty, R. 0., and Jackson, M. T. 1966. Plant communi-
ties. In Lindsey, A. A. (ed.), Natural Features

of Indiana (Indianapolis: Ind. Acad. Sci.):
26A—96.

 

 

Cowles, H. C. 1901. The Plant Societies of Chicagg
and Vicinity. Geogr. Soc. of Chicago Bull. No. 2.
Chicago: Univ. of Chicago Press.

 

 

Cowles, H. C. 1901. The physiographic ecology of
Chicago and vicinity; a study of the origin,
development, and classification of plant societies.
Bot. Gag. 31: 73—108, 1U5—82.

Shreve, F. 1917. A map of the vegetation of the United
States. Geog. Rev. 3: 119—25.

 

Fuller, G. D. 1925. The Vegetation of the Chicago
Region. Chicago: Univ. of Chicago Press.

 

Gordon, R. B. 1936. A preliminary vegetation map of
Indiana. Amer. Midl. Nat. 17: 866—77.

 

Kuchler, A. W. 196“. Potential Natural Vegetation of
the Conterminous United States. New York:
Amer. Geog. Soc. Spec. Pub. No. 36.

 

Potzger, J. E., and Keller, C. O. 1952. The beech
line in northwestern Indiana. Butler Univ. Bot.
Stud. 10: 108—13.

 

27.

28.

29.

30.

31.

32.

33.

3M.

35.

36.

37-

38.

63

Potzger, J. E., Potzger, M. E., and McCormick, J.
1957. The forest primeval of Indiana as recorded
in the original U. S. land surveys and an evalu-
ation of previous interpretations of Indiana
vegetation. Butler Univ. Bot. Stud. 13: 95—111.

 

Rohr, F. W., and Potzger, J. E. 1950. Forest and
prairie in three northwestern Indiana counties.
Butler Univ. Bot. Stud. 10: 61-70.

 

Lindsey, A. A. 1961. Vegetation of the drainage—
aeration classes of northern Indiana soils in

1830. Ecology A2: M32-36.

Lindsey, A. A., Crankshaw, W. B., and Quadir, S. A.
1965. Soil relations and distribution map of
the vegetation of presettlement Indiana. Bat.
Gag} 126: 155-63.

Meyer, A. H. 1950. Fundament vegetation of the Calu—
met Region, northwest Indiana-northeast Illinois.
Paps. Mich. Acad. Sci. Arts Letters 36: 177-82.

 

Potzger, J. E., and Friesner, R. D. 19U0. What is
climax in central Indiana? A five—mile quadrat
study. Butler Univ. Bot. Stud. A: 181—95.

 

Finley, D., and Potzger, J. E. 1952. Characteristics
of the original vegetation in some prairie coun—
ties of Indiana. Butler Univ. Bot. Stud. 10:

 

11A—18.

Fuller, G. D. 1935. Postglacial vegetation of the Lake
Michigan region. Ecology 16: “73-87.

Sears, P. B. 1948. Forest sequence and climatic change

in northeastern North America since early Wiscon—

sin time. Ecology 29: 326—33.

Just, T. 1957. Postglacial vegetation of the north
central United States (Abst.). Geol. Soc. Amer.
Bull. 68: 1895.

 

Zumberge, J. H., and Potzger, J. E. 1956. Late Wis—
consin chronology of the Lake Michigan basin cor—
related with pollen studies. Geol. Soc. Amer.
Bull. 67: 271—88.

 

Guennel, G. K. 1950. History of forests in the glacial
Lake Chicago area. Butler Univ. Bot. Stud. 9:
1A0—58.

 

39.

U0.

Al.

U2.

A3.

H7.

A8.

“9.

50.

51.

6A

Potzger, J. E. 19A6. Phytosociology of the primeval
forest in central-northern Wisconsin and Upper
Michigan, and a brief post—glacial history of the
lake forest formation. Ecol. Monogr. 16: 211-50.

 

Benninghoff, W. S. 1963. The prairie peninsula as a
filter barrier. Proc. Ind. Acad. Sci. 73:
116-2“.

 

Potzger, J. E., and Friesner, R. C. 1939. Plant mi—
grations in the southern limits of Wisconsin
glaciation in Indiana. Amer. Midl. Nat. 22:
351—68.

 

McQueeney, C. R. 1950. An ecological study of the re—
lationship between direction of slope, elevation,
and forest cover in Brown County, Indiana. Butler
Univ. Bot. Stud. 9: 239—69.

 

Gleason, H. A. 1968. The New Britton and Brown Illus-
trated Flora of the Northeastern United States
and Adjacent Canada. New York: Hafner.

 

 

 

Harlow, W. M., and Harrar, E. S. 1958. Textbook of
Dendrology. New York: McGraw—Hill.

 

 

Morgan, M. D. 1969. EcolOgy of aspen in Gunnison
County, Colorado. Amer. Midl. Nat. 82: 20A—28.

 

Harman, J. R. 1970. Forest types and climatic modi—
fication along the southeast shoreline of Lake
Michigan. Annals Assoc. Amer. Gegg. 60: In press.

 

Ward, R. T. 1956. The beech forests of Wisconsin——
changes in forest composition and the nature of
the beech border. Ecology 37: 407—19.

U. S. Soil Conservation Service. 1967. Lake County
Soil—Survey Maps. Unpublished.

 

 

Soils of the North Central Region of the United States.
North Central Region Pub. No. 76} Madison: Univ.
of Wis. Agric. Exp. Station.

 

Blalock, H. M. 1960. Social Statistics. New York:
McGraw—Hill.

 

Bartelli, L. J., and Peters, D. B. 1959. Integrating
soil moisture characteristics with classification
units of Illinois soils. Soil Sci. Soc. Amer.
Proc. 23: 1&9—51.

 

52.

53.

5A.
55-
56.
57.
58.
59.

60.

65

Jamison, V. C., and Kroth, E. M. 1958. Available
moisture storage capacity in relation to textural
composition and organic matter content of several
Missouri soils. Soil Sci. Soc. Amer. Proc. 22:

189-92.

 

Lund, Z. F. 1959. Available water-holding capacity
of alluvial soils in Louisiana. Soil Sci. Soc.
Amer. Proc. 23: 1—3.

 

 

Gaiser, R. N. 1952. Readily available water in forest
soils. Soil Sci. Soc. Amer. Proc. 16: 334—38.

 

Buckman, H. C., and Brady, N. C. 1960. The Nature and
Properties of Soils. New York: MacMillan.

 

 

Franzmeier, D. P., and others. 1960. Relationship of
texture classes of fine earth to readily available
water. Trans. 7th Internat. Congr. Soil Sci.

1: 35u—63.

 

Friesner, R. C. 1942. Dendrometer studies of five
species of broadleaf trees in Indiana. Butler
Univ. Bot. Stud. 5: 160-72.

 

Changnon, S. A. 1968. Precipitation Climatology of
Lake Michigan Basin. Urbana: Ill. St. Water
Survey Bull. 52.

 

 

Borchert, J. R. 1950. The climate of the central
North American grassland. Annals Assoc. Amer.
Geog. U0: 1—39.

 

Transeau, E. N. 1905. Forest centers of eastern
America. Amer. Naturalist 39: 875—89.

 

CHAPTER IV

THE LAKE BREEZE

Review of the Literature

 

The problem of climatic modification by the Great
Lakes has received considerable attention. Studies have
been primarily devoted to describing the influence exerted
by the lakes upon climatic elements, such as temperature
and amount of snowfall, in their vicinity. A selective
review of literature relating to various aspects of lake
modification is presented in Chapter 1. Interest in the
dynamic interaction between the lakes and atmospheric
processes over them and over adjacent land is more recent
and has been the subject of fewer investigations. One as—
pect of this interaction which has been the focus of an
increasing number of studies concerns the development and
climatic impact of lake breezes.

Lake breezes, which are equivalent to sea breezes,
illustrate on a small scale the principles involved in the
conversion of radiant solar energy to kinetic energy of
atmospheric motion (1). Due to several factors, of which
the turbulent mixing of water may be the most important (2),

water warms up much more slowly in response to incoming

66

 

67

solar radiation than does land. On clear summer days, near
the shoreline of a large water body, expansion of air over
the heated land surface results in a rising of isobaric sur-
faces and thus produces a horizontal pressure gradient aloft
with higher pressure over land. In response to this gra-
dient, air movement aloft occurs from the land toward the
water. This action increases surface pressures over the
water while decreasing those over the land, thus setting

up a second pressure gradient, opposite in direction to the

first one, across the shoreline at the surface. Lake or

 

sea breeze flow is a response to this pressure gradient.
The offshore current aloft is referred to as the return
flow, although it must actually begin before the lake
breeze can be established (3).

Perhaps the earliest reference to the occurrence of
lake breezes in the vicinity of the Great Lakes appeared in
1799 (A); the diurnal alternation of onshore and offshore
winds near Lake Erie were discussed. Another early discus—
sion of lake breezes, including their causes and influence
on the climate of the Chicago region, was presented by
Hazen (5).

The basic characteristics of lake breeze dynamics
are now quite well understood. The most important factors
controlling lake breeze development are the magnitude of
the land—water temperature contrast and the strength and

direction of the regional wind (6,7). As would be expected,

 

68

lake breezes are normally most frequent during late spring
and early summer when land heating is intense but lake
waters are still cold (3). Excessive cloudiness can de—
crease heating of the land and therefore prevent lake breeze
formation. Hall (8), working in the Chicago area, found
that offshore winds in excess of 10 to 12 miles per hour
prevented the development of a lake breeze; with onshore
winds, a lake breeze circulation was able to exist at

slightly higher wind speeds (15 mph). Olsson (3) reached

 

similar conclusions in the same region. In addition, local

 

factors such as topography and the shape of the coastline
influence the characteristics of lake or sea breezes (9,10).

In the absence of superimposed regional flow, lake
breezes first develop at the shoreline where the horizontal
temperature gradient is strongest (11,12). With an off—
shore wind, however, warm land air is advected over the
water and the steepest temperature gradient may occur off
shore; in such cases, a lake or sea breeze would form ini—
tially over the water (1). During the day, the lake breeze
advances inland and is usually deflected by the earth's
rotation in a clockwise direction so as to become more
nearly parallel to the shoreline (9,13).

Two distinct types of sea (lake) breezes have been
recognized (2,1M). The first of these is identified as the
frontal type and generally occurs when the sea breeze is

opposed by the gradient flow. A breeze of this type has a

 

69

well defined front, may not begin to advance inland until
afternoon, and usually advances quite suddenly; passage of
the front often brings a sharp temperature drop and a rise
in relative humidity. A non—frontal sea breeze, on the
other hand, begins early in the day and brings gradual
rather than abrupt changes in temperature and relative
humidity. This type occurs most frequently on days when
onshore regional winds reinforce the lake breeze. Estoque
(15) believed that development of frontal characteristics
does not occur in such cases because initial onshore flow
prevents excessive heating of the land. It seems likely
that many sea and lake breezes are intermediate between
these two types.

Moroz (16) investigated one lake breeze occurrence
on a day of weak gradient flow on the eastern shore of
southern Lake Michigan. At 0900 local time surface winds
were offshore, probably representing a land breeze. The
lake breeze crossed the shoreline at 1000, three hours
after inland air temperature became equal to the lake sur—
face temperature. Passage of the lake breeze front pro-
duced a temperature drop and a rise in relative humidity;
these changes were marked near the shoreline but became
indistinct farther inland, indicating modification of air
properties by heating from below. The front apparently
progressed inland in surges rather than at a steady rate;

maximum inland penetration of over 10 miles was reached

 

 

70

about 1800 when the lake—inland air temperature difference
began to decrease. Maximum depth of the lake breeze was
approximately 2M00 feet. The maximum onshore velocity was
15 miles per hour and occurred over the lakeshore about the
time of maximum temperature contrast between water and non—
1ake breeze air. Studies by Munn and Richards (9), Moroz
and Hewson (l7), and OlssOn and others (3,18) have sup-
ported these observations. Olsson (3) also reported that
the lake breeze front had a slope of approximately 1:20;
this can be compared with the average value for cold fronts
of 1:50 to 1:150 (19). Estimates for sea breezes range
from 1:20 to 1:100 (1U,20).

On days with very weak gradient conditions, lake
breezes may develop symmetrically around Lake Michigan (3).
Because the regional prevailing wind is southwesterly,
however, lake breezes on the average extend farther inland
on the southeastern shore of Lake Michigan than they do on
the southwestern shore (21). The frequency with which lake
breezes occur in the vicinity of the Great Lakes has not
been studied extensively. Biggs and Graves (6), working on
the western shore of Lake Erie, observed an average of 23
lake breeze days per June—August period over three years;
they eliminated all days with onshore gradient winds from
their study. Hall (8) stated that lake breezes are almost
daily occurrences at the shore near Chicago, but noted that

over a three year period an average of only 11 breezes per

 

 

71

year penetrated as far as eight miles inland. Long—term
figures for the eastern shore of Lake Michigan are not
available.

The apparent suppression of summertime convection
and precipitation by Lake Michigan and the other Great
Lakes has received considerable attention. Hazen (5)
noted that Chicago received less precipitation on days
with onshore winds than surrounding inland stations did,
and Eshleman (22) observed that stations on the Wisconsin

side of Lake Michigan received more summer rainfall than

 

those on the eastern side. More recent investigations by
Changnon (23), Blust and DeCooke (2H), and Stout and Wilk
(25) have suggested that summer precipitation is reduced
at stations along or on Lake Michigan. Weiss and Kresge
(26) and Williams (27), however, did not find any signifi—
cant reduction of offshore precipitation. Lansing (28)
observed the apparent suppression during the summer of
cumulus cloud formation over or near the lee shore of Lake
Ontario. Other studies present evidence for the suppres-
sion or dissipation of cumuli (29), squall lines and air
mass showers (25,30), and thunderstorms (31) by Lake Michi-
gan. Sometimes, for reasons not yet well understood, squall
lines and air mass showers pass over the Lake with little
apparent modification (29,32).

On summer days a mesoscale ”lake high" often develops

over Lake Michigan (8,32). This dome of cool and very

 

72

stable air, resulting from a net downward flux of heat and
subsidence over the Lake, is probably responsible for the
suppression of cloud formation over the Lake (29,32).
Olsson (3) found that the "lake high" reached a maximum
intensity of A millibars by early evening. Satellite and
aerial photography have shown that the lake—induced cloud-
free zone often extends inland on the Michigan shore as
much as 20 miles.

A form of climatic modification associated with lake
breezes which has received less attention is related to
low-level convergence near the lake breeze front. Several
sea breeze studies have indicated that strong vertical air
movement occurs near the front and can induce cloud forma—
tion (2,20,33). Leopold (34) reported local rainfall
"islands" in Hawaii which corresponded with the mean posi-
tions of sea breeze fronts. Byers and Rodebush (35) at—
tributed the high frequency of summer thundershowers over
central Florida to convergence of two sea breezes from oppo—
site sides of the peninsula. Estoque (l2) theoretically
demonstrated the existence of convergence and upward air
movement at the sea breeze front.

Moroz (l6) and Olsson (3) have reported strong hori—
zontal convergence and large vertical velocities near lake
breeze fronts on the eastern shore of Lake Michigan. Other
studies have found that bands of cumulus clouds frequently

develop along the lake breeze front around Lake Michigan

 

 

 

 

73

and that shower activity can occur there (32,36). Shenfield
and Thompson (37) and Moroz and Hewson (17) have presented
evidence suggesting that under certain conditions the pres—
ence of a lake breeze can be an important factor in trig—
gering or intensifying localized thunderstorms.

Several investigations have indicated that lake breeze
convergence may be particularly important adjacent to the
southeastern shore of Lake Michigan near the area of the
present investigation. Estoque (15) found from theoretical
considerations that vertical motion near a sea breeze front
might be especially strong when the geostrophic wind is
parallel to the shore with low pressure over the water;
this situation appears to be analogous to that along the
southeastern shore of the Lake during southwesterly flow.
Lyons (32) observed that a band of towering cumuli can
develop parallel to the southwestern shore of the Lake
during northwesterly flow. Similar activity might be ex—
pected along the southeastern shore during the more frequent
southwesterly winds. Schaefer (38) stated that a street of
cumulus clouds is commonly observed extending along the con-
vergence zone south and southeast of Lake Michigan. A pat—
tern of higher thunderstorm precipitation extending from
northwestern Indiana into Michigan has been described by
Changnon (39). Finally, Lyons and Wilson (29) have sug—
gested that convergence and cloud formation may occur along

the southeastern shore of the Lake even in the absence of

7U

a lake breeze when winds are southwesterly. This would re—
sult from veering of the wind as it passes over the low-
friction lake surface, producing convergence with the un—
affected flow inland.

Reviews of the literature on sea and lake breezes
have been presented by Schroeder (U0), Munn and Richards

(9), Olsson (3), and Baralt and Brown (U1).

The Climatic Hypothesis

 

Changnon (U2) has described an "island" of high warm—
season precipitation centered on La Porte, Indiana, and has
attributed it to the effects of atmospheric pollution from
the Gary—Chicago industrial complex. Evidence of this pat—
tern has appeared in other studies as well (21,U3,UU).

Ogden (U5), on the basis of rainfall studies near an Austra-
lian steelworks, however, has expressed doubt that the La
Porte anomaly can be attributed to industrial causes. He
believed that increased cloud droplet concentration as a
result of nucleii addition could reduce mean droplet size
and therefore reduce the likelihood of coalescence suffi—
cient to produce rainfall. He observed variations in five—
year precipitation means of individual stations similar to
those which have taken place at La Porte since 1925. These
variations appeared to be unrelated to changes in neigh—
boring stations or to industrial activity.

Hodgins (U6) found that for the five year period 1953—

1957 the most frequent July circulation pattern over the

75

eastern United States resembled that depicted in Figure 13.
The dominant feature of this pattern is an anticyclonic sys-
tem situated over the southeastern states resulting in south-
westerly flow over the Midwest. Such a synoptic situation,
probably associated with a mid-continent tropospheric ridge,
would bring higher than normal temperatures to the Great
Lakes region.

Under these conditions, with high daytime tempera—
tures, the dome of cold air over Lake Michigan probably
would be strongly developed and the front of its associated
lake breeze sharply defined. Along the southwestern shore
of the Lake, where the regional flow is more normal to the
front, the lake breeze would be prevented from advancing
inland and might even be displaced over the water (Figure 1U).
On the southeastern and eastern shorelines, however, the
lake breeze would advance inland. Satellite photographs
have indicated that this pattern does occur (32). Varia-
tions of this pattern would develop under westerly or north—
westerly winds.

Since the degree of lake breeze penetration is a func—
tion of several factors, including wind direction, wind
speed, and land—water temperature contrasts, there would
be day—to—day fluctuations in maximum inland advance.
Nevertheless, a mean frontal position could be identified.
The hypothesis of this study is that on days of regional

flow with a westerly component, the mean location of the

76

D24

-4

’2 I-
0""

'quv
S

‘0’.’€,

‘80

   

I0|6

SOURCE: U.S. WEATHER BUREAU

0 I00 100 300 400
Miles

 

noun l3
SURFACE WEATHER MAP
August 29, I969

 

 

Q— m-30.u

 

77

 

10‘

 

 

ONO—

   

   

 

     

 

\

_
_
_
_
_
_
m 23......)
_
L
_
_
_
.

      

_
“I ..... II- ‘ —
_ .
_ . _
L n
1
l _ i
C _ >30 "
_ atom-... IIIIII ‘ u 0 _
”— o\flumm\II Ewan-MI! .
\\ \ P M
‘ ..J \\ \ / _
\\..\\ w*VW// l
_ 252:2: / .
_ 3:3 / 4

02:5 ._<ZO_0m~_ >d¢uhmm31h30m 1:3
...ZOzm uNumam m¥<._ “—0 202.30.. nmN_mthO.—>I

F_____._____

 

 

 

 

78

lake breeze front, and its associated convergence zone, lies
in the vicinity of La Porte and might be causally related
to the La Porte rainfall anomaly (Figure 12).

It is beyond the scope of the present study to demon-
strate whether increased precipitation does in fact fall in
the vicinity of La Porte when the lake breeze convergence
zone is situated near that city. However, some comments
regarding the processes which might bring about such a
precipitation pattern under those conditions are perhaps
desirable. Convectional activity, as a result of conver-
gence, presumably would occur along the length of the lake
breeze front as it extends inland toward La Porte and
beyond. Under suitable atmospheric conditions, this con—
vection could initiate cloud formation which might lead to
precipitation. Rainfall would naturally not begin at once,
however, as time would be required for the clouds to or-
ganize and grow. During this time they would be moved
down-wind along the convergence zone by the regional flow;
Lyons and Wilson (29) have reported such movement by cumuli.
At some point along the front, precipitation might begin;
the location of this point would vary from day to day de—
pending on the degree of lake breeze development and a com-
plex of other factors, but presumably a mean precipitation
Zone would be established. If so, that region might receive
Ineasurably more rainfall than surrounding areas when lake

breeze development is favored.

79

Results of the Survey

 

Twenty—two lake breeze days were identified which met
the criteria outlined in Chapter 11 (see Appendix V).
Tables 7—9 indicate, for 1000, 1300, and 1600 EST, the num—
ber of occurrences during those days of winds from 16
compass directions at the six instrument stations (at the
Ogden Dunes station, only eight compass points were used in
recording wind direction). Figures 15—17 present the in—
formation from Tables 7—9 in a spatial context. The six
instrument sites have been abbreviated in this discussion
as follows: Argonne (ARG), Ogden Dunes (OGD), Westville
(WSV), Wanatah (WAH), Michigan City (MCY), and South Bend
(SBD).

Several patterns can be detected in Figures 15—17.
For the hour 1000 EST, there is considerable similarity
between the wind roses for all stations, although that for
Michigan City appears to show some lake breeze influence.
By 1300 the MCY rose clearly indicates the influence of
lake breezes, while it appears that Ogden Dunes, Westville,
and South Bend occasionally experienced lake breeze flow.
The pattern for 1600 suggests slightly increased lake
breeze influence at OGD, WSV, and possibly as far inland
as Wanatah, about 18 miles from the lakeshore. South Bend,
on the other hand, appears to have experienced less lake
breeze flow at 1600 than at 1300. At both MCY and OGD,

winds off the lake shifted from northwesterly at 1300 to

8O

.mocsm copmo

pa ems: chHpompHe pgmHm*

 

 

 

m H m m H m m m H H m gapacm3

H m m m m m H H m scam cpsom

H m m m m o H mHHH>pmm3

m H m m m H H H H H spHo camH20H2

H 3 M NH H H *mmcsm cmemo

m 0H H 3 m H H H accomsa

eHao 322 32 323 3 3m3 3m 3mm m mmm mm 3mm 2 222 32 222 2 cOHQMpm
. .emm OOOH
”mth. mNmmch mxmd OSPINAUCOBE wCflcHSQ mCOHpomkflm CmmeHm EOLQ UCHB rHO mmoflmfiflzooo ,HO .HmflESZII. N. Mdmxfiw

81

.mocsa copwo pm pom: mcoHpoosHo pszm*

 

 

H m m q H m m H m H prmcm3
m 3 m m m m m pcom Epsom
m m m m m m H m oHHH>umo3
m m m H H m m 38 2332on
m m m m m H m *mocsa copwo
H m H m 3 m occows<
EHmo 3ZZ 3Z 3Z3 3 3W3 3m 3mm m mmm mm mmm m mzm m2 mZZ Z COprpm

 

”whoa mmompm oxmq ozplzpcoze

.Bmm OQMH
mcHHSQ mcoHpomHHm cooprm Eopm UQHZ go moocopHSooo

we LoQESZII.w mqm<B

82

.22232 Cosmo 22 wow: wCOHpooHHp panm*

 

 

m m m m m 3 H H H H 2232223
H m 3 m 3 m m H H H 2222 22:02
N m H m 3 m m m oHHH>pmoZ
3 H m m H 2 m H spHo camHnon
m m m m 2 m m *mmcso 22220
H m m m 3 m m H occomp<
sHmo 322 32 323 3 323 32 322 m 222 22 222 2 222 22 222 2 30H2222

 

.Bmm oomH
”mzma omoomm oxmq ozpl3ucose wCHpsp mQOHpooHHQ comprm E033 22H: mo moososhzooo

go HOQSSZII.m mqm<9

83

n— m-DOI

 

 

10w

 

 

 

 

 

 

 

 

         

    

j

_ .1

_ L

omflofll Hm IUJuI—mflo _ u _
J 23 2.2-522:4 _ _
z I .
L H .

_ _ _

..... .. H u _ _L

“HI 21> _ . __

_ u _

__ _ _ 1

a. _ _ _

_ . _

_ _ i
. _

a: —..JH _ M

_ 23.222 _ if.

_ ............. I 3:: m

l

52 coo.

m><0 uwazm w¥<._ NN 02_¢DD 02.; "___O mm.UZmDOm~—m ._<ZO_.—.Uu¢_o _

 

 

8U

op unaua

 

 

, ---..3——- ...... ___._ --

 

   

 

 

I II -- . IEIIIIIIII illlj

 

 

  

2<0_:U_2
_ mx<..

0¢(

  

5m. oom— .
“>35 2N3: 32.. «a 02:2. 92.3 “.0 3522203: 220.5223 1

 

 

 

85

k— manor.

 

 

.Oq

 

 

         

    

L
_
«3.3 _
0% . _
J 23 ...-£33... 4 _ _
z . .
L _ _
_ _
3 ..... .. _ _
_ n _
_ _ _
.... u .
“a _ _
_ n _
_ _
_
LA r _
on» u .
_ 23.22: _
_ mx<._

...mm 002
m><n meuan m¥<._ «N 02.540 n2_>> “_O mwGZmDOmuu ..(ZOZUqu

 

 

__. ——-———~——~-——- —H‘-3_

_ ..-.---...__.—_—.._ _

.I____._-_._.___

 

 

86

northeasterly at 1600, probably as a result of deflection
by the earth's rotation (9).

In an effort to obtain a clearer picture of mean lake
breeze penetration, the number of days on which lake breeze
flow apparently reached each station was recorded. Some
subjectivity was involved in determining lake breeze pres—
ence or absence. Essentially, any day during which the
northerly component of the wind increased markedly at a
station, and on which a similar shift at Argonne was not
recorded, was counted as a lake breeze day. Figure 18
presents the results in per cent of MCY lake breeze occur—
rences. A line approximately delineating the extent to
which lake breezes penetrate during about one half of
Michigan City's lake breeze days was drawn; this line could
be considered as estimate of the mean position of the lake
breeze front. It appears that this zone crossed the shore—
line near Ogden Dunes and may have passed near the city of
La Porte. With the limited number of stations presently
available in the study area, however, such conclusions are
only tentative.

In order to further visualize lake breeze penetra—
tion, the Michigan City lake breeze days were divided into
tWO groups according to the prevailing direction of the
I’EEgional surface wind at the Argonne station. One group
COnsisted of days on which the wind was from 1800 to 2690

(thE? southwest quadrant), the other of days with winds from

 

87

up w-:°_u

 

ET

 

 

 
    

  

. Z<0_:U_E
_ ux<._

mZO_h<._.m «5.3.0 ._.< auhUm—hn
muNmmcn ux<.. >20 Z<0.:U_S "_O ...2uU «mm

ONO.

o5;

 

 

 

_

_

L.
IIL

 

88

270° to 3590 (the northwest quadrant). Each group contained
eleven days. Again the number of those days on which lake
breeze flow reached each station was determined. Figures

19 and 20 present the results as per cent of MCY lake breeze
days.

It is evident that days with westerly to northwesterly
regional air flow were more favorable for inland penetra—
tion of the lake breeze in northwestern Indiana than those
with winds from the southwest quadrant. When the former
situation prevailed it appears that over 60% of the lake
breezes recorded at Michigan City penetrated at least as
far inland as La Porte and nearly 20% reached Wanatah, about
18 miles from the Lake. Under regional flow from south of
west, however, perhaps less than U0% of the lake breezes
reached La Porte and none were detected at Wanatah.

Figures 18—20 also indicate a sharp decrease in lake
breeze frequency westward through Indiana along the lake—
shore. During the days examined in this study, lake
breezes occurred approximately one—half as often at Ogden
Dunes as at Michigan City, 18 miles to the northeast. Most
of this reduction occurred when the regional flow was from
the southwest quadrant; lake breeze frequency at Ogden Dunes
was only one-fourth that at Michigan City when that situation
existed.

It appears from Figures 18-20 that, for the 22 days

analyzed, the lake breeze front may have had a mean position

89

2 mun-0: z

 

a?

 

 

 

     

“3.1

on °~ w. n o

:3 23:522.. 4

u.
I

“I: 13:4

_
lfilib
_ ._

33‘ 2 _
— otb‘Dd . 090‘
KN Il‘ III III \Iafihml llllll
can. _:J \ ”3:90.90 #3 a

. 2(0_:U=¢
_ mx<d

   

    

o
0.24

30..“— mu<mu3m d<ZO_Om¢ >._¢m._.mu>>1._.DOm “_O m><n 20 mZO_.—<._.m

~3th ._.< curvy—mo mmNmuzn 3:: >20 Z<O_IU_E “_O hZuU «mm

ano—

 

 

 

 

 

 

90

on muse:

 

36..

 

 

     

«3.5

On On p n o

Comm oCOB—Bhuafl— ‘

u.
l

m .230 _
_ _
_:.... IIIIIII _
. \\ \\\...Oumwflflzhu I I,
_ \ \d9\000 4.3 v0 _ ///H
. \ a) a _ s _ /
v . /
\\ L_‘ 23230 _ 000‘ n /
\ . .
n3 \\ # _
cad \\ ......
\\ u _
_ 23.22:
_ mx<d

 

   

    

9:;

30: m0<m¢3m ._<20_0m~_ >H¢mhmw>>zh¢OZI>a¢mhmm>> "_O m><n ZO

mZO_.—(._.m «my—ho ._.< 0:09—06 muNmmun u¥<._ >._._0 Z<O_:0.¢< “_O PZuU awn

 

 

Ill".

0k:

 

 

91

in the vicinity of La Porte, particularly during those days
on which the prevailing regional wind was westerly to north—
westerly. A denser network of observation stations and a
longer period of observation would be required to confirm
the apparent pattern of lake breeze penetration and accu-
rately determine the mean frontal position. However, these
findings tentatively suggest that the lake breeze may be a
factor in the regional precipitation pattern.

Although not directly related to the hypothesis under
consideration, further analysis of the data might contribute
to an understanding of the conditions which govern lake
breeze development in northwestern Indiana. Thirty—seven
days between June 11 and August 31, 1969, during which the
regional air flow possessed a westerly component and fronts
did not pass through the study area, were identified.

These included the 22 Michigan City lake breeze days and

15 others. For each of these days, the following values
were calculated: (1) the difference between Lake Michigan
water temperature at Chicago (5) and the maximum air tem—
perature measured at the Argonne station; and (2) the mean
of the hourly wind speed readings from 1000 to 1600 EST,
inclusive, at Argonne. These two variables, plus wind
direction, are probably the primary controls of lake breeze
formation and inland penetration. Argonne was selected to
represent inland conditions because it would be little af—

fected by lake breeze flow.

92

The thirty—seven days were then plotted on a coordi-
nate system in which the vertical axis represented the land—
water temperature difference (AT) and the horizontal axis
represented the mean wind velocity at Argonne (w). Two
different symbols were used depending on whether or not
a lake breeze occurred that day at Michigan City. Figure 21
presents the results. It was found that a line representing
a ATzw ratio of 2.2 1 separated lake breeze and non—lake
breeze days with an accuracy of 65%. If ratios between 2.0:1
and 2.U:l are considered transitional, and one day on which
the reported lake temperature seemed anomalouly high is not
included, the accuracy rises to 72%.

In Figure 22, only days on which the regional wind was
from south of west were plotted. Figure 23 displays those
days with regional air flow from the west or north of west.
For the southwesterly wind days, a ATzw ratio of slightly
less than 2.2:1 separated lake breeze and non—lake breeze
days with 77% accuracy. Days of northwesterly winds were
too few to give very meaningful results; however, a line
representing a ATzw ratio of 0.9 1 provided 79% accuracy
in separating lake breeze and non—lake breeze days (again
not considering one day with seemingly anomalously high
recorded lake temperature).

The graphs thus indicate that greater land-water
temperature contrasts and/or weaker regional winds are re—

quired for develOpment of lake breezes at Michigan City

_-—-_.

Argonno-Loke Michigan Tompovoiuvo DiIIuonco (AT)

93

 

 

 

4oI
0 um um: on
u NON-LAKE BREEZE on
I
”I a /
/
/
/
/ u
/
/
/
JOI’ //n
/
'c-‘x
.,\‘/
a .Q/
\'/
o D/
25L 0 //
0 ° 4/
O o O //
/
/
I /
aoI-
. U // O
. ° ° /
// °
0 / o
I I o O O / O D
i 0 /
ISI' 0 0 o /
o g// a
/ o
/
O //
I ° / 0
I0}- /
. /
/
/
I /
/ O
I /
I //
SI /
I /
/
I /
/
I /
/
__ f _L_-_--_A _-,.1.3L-_3_.ll. _ -....L .. _L _L__ __1_ _-__ l.-. _ - l L l J
2 ¢ 6 I I0 I2 I4 l6

mum uouuv wmo srnomnoommoo “can."
noun 2I
LAKE BREEZE AND NON-LAKE BREEZE DAYS AT MICHIGAN CITY PLOTTED BY
LAND-WATER TEMPERATURE CONTRAST AND MEAN WIND SPEED:
REGIONAL FLOW FROM IBO°-360° INCLUSIVE

IATI

Argonne-Lulu Michigan Temperature DHIoronco

40

35

30

25

20

 

9U

O LAKE BREEZE DAY

0 NON LAKE BREEZE DAY

 

 

u /
/
/
/
/ n
/
/
/
/
/€ ’
//
9/
JV
0 -.*‘/
\
p/
/
/
/
//
0 ° /
/
/
/
/
/
D /
o /
/
/
U //
/
o a
o o // a
O
3 /
o / a
/
/
/
/
/ D
/
/
/
/
/
/
/
/
/
/
/
/
/
/
l 1 L, L, 1,331 l__.3L .. .I - ,1]. - , . I. -3 _J32” __L.._._. __L._-_- ...L..._____L l l J
2 ¢ 6 5 I0 12 I4 I6

MEAN HOURLY WIND SPEED IWI TOGO-1600, ARGONNE

FIGURE 22

LAKE BREEZE AND NON LAKE BREEZE DAYS AT MICHIGAN CITY PLOTTED BY
LAND-WATER TEMPERATURE CONTRAST AND MEAN WIND SPEED:
REGIONAL FLOW FROM IBO°-269° INCLUSIVE

Algonno-Loho Michigan To-povciuro Di". 'onu IATI

95

LAKE BREEZE DAY

0 NON-LAKE BREEZE DAY

 

O
25- O
D 0
20-
D
0
ISI- 0
8 3
I /
/
O //
o,‘.‘//
D '“2 ’
\- z
0”
I0» /
/
/
/
/
/
/
/
//
o /
/
/
/
I /
//
5L //
. /
/
I /
/
/
‘ /
/
/
/
//
L /// | o n
/
1 L 4 4 j __ L 4 1 1 L _1 1 J
2 4 6 ID I2 I4 I6

mum uounu wmo SPEID‘WI,IOOO-1600.ARGONNE
noun 23
LAKE BREEZE AND NON-LAKE BREEZE DAYS AT MICHIGAN CITY PLOTTED BY
LAND-WATER TEMPERATURE CONTRAST AND MEAN WIND SPEED:
REGIONAL FLOW FROM 270°-360° INCLUSIVE

96

during a southwesterly flow than with westerly or north-
westerly flow. During the study period, lake breezes did
not develop under southwesterly regime when the temperature
contrast was less than 1U°F or when the wind speed exceeded
11 miles per hour. With westerly to northwesterly flow,
lake breezes formed with a temperature contrast as low as
70F; maximum favorable wind speed appeared to be about the
same as for southwesterly flow.

The same 37 days were also divided on the basis of
whether lake breeze development seemed to take place at
Ogden Dunes and were plotted as above. Figure 2U presents
the results. A line representing a AT:w ratio of 2.9:1
differentiated lake breeze and non—lake breeze days with
73% accuracy. The following summary statements can be made
regarding lake breeze occurrence at Ogden Dunes during the
study period: (1) lake breezes developed on markedly fewer
days at Ogden Dunes than at Michigan City (13 vs. 22); (2)
most of this reduction occurred during southwesterly air
flow (3 lake breeze days at OGD under such flow vs. 11 at
MCY); (3) lake breezes occurred under southwesterly flow
at Ogden Dunes only under conditions of high land—water
temperature contrast (16°F or more) and weak regional flow
(6 miles per hour or less); (U) the steeper slope of the
ATzw line, as compared with that for Michigan City, indi—
cates that on the average greater land-water temperature

differences and/or weaker regional winds are required for

 

Argonne-Lake MitIII'an Tonpgmgu,. Dunn"... IAII

 

97

 

 

40
/
/
/
o LAKE "zen DAY /
/
33, o NON-LAKE usezt on // .
Dot I on 0! SW REGIONAL now /
/
/ I
/
/
/
JOI- .‘/ I
“9/
‘Ir/
.~!‘/
\.
V/
I /
/
/
° /
25» /
° /
o / o I
/
I I / I
/
/
/
/
20. 4
/
I / o
/
/
/
I / O
. O // O . -
I5? // II
/ R .
o / I
/ a
/
o / I
/
/0
IO- //
/
/
/
/
/
/ o
/
/
/
S - /
/
/
/
/
/
/
/
/ u
/ 1 J A l J A A 7_L 1 L ._J._.Ll_._2_L_ —1 L 1 #4
2 4 10 I2 I4 16

mun H060!” wmo ”“00 (W), moo-woo, “corms
noun 24
LAKE BREEZE AND NON-LAKE BREEZE DAYS AT OGDEN DUNES PLOTTED BY
LAND-WATER TEMPERATURE CONTRAST AND MEAN WIND SPEED=
REGIONAL FLOW FROM IBO°-360° INCLUSIVE

98

lake breeze development at Ogden Dunes; this is under—
standable since OGD is situated on a more windward shoreline
than is MCY.

The ratio of land—water temperature contrast to mean
inland wind speed used above is similar to the "lake breeze
index" derived through dimensional analysis by Biggs and
Graves (6). The only major difference is that the latter
index utilized the square of wind speed rather than the
measured value. Biggs and Graves found that their index
separated lake breeze and non—lake breeze days on the
western shore of Lake Erie with 95% accuracy. Several
factors might help explain the lower accuracy attained in
the present study. First, the study period of one season
was too short to allow accumulation of sufficient data.
Second, the station used to represent inland temperature
and wind conditions (Argonne) is a considerable distance
west of the sites being investigated (about 60 miles from
Michigan City) and may not accurately indicate the local
situation in which a lake breeze would have to develop.
Finally, the water temperatures used were taken at a depth
of about six feet near Chicago (8). Although one study has
found that lake surface temperatures are nearly uniform
within ten miles of the shore between Benton Harbor and
Chicago (51), there may be as much as lOOF difference be—
tween surface temperatures and those at 6 feet (8). Sur-
face temperature readings nearer the study area would have

been desirable.

99

During much of the summer of 1969, anomalous weather
conditions prevailed over the western United States (U7,U8,
U9). In June, a deep trough at upper tropospheric levels
over the North Central States brought unusually strong
northerly flow, frequent storms and persistent cloudiness
to the Great Lakes region; these factors resulted in nega—
tive temperature departures which did not favor lake
breeze development. During July the pattern normalized
somewhat but temperatures remained slightly below normal.

Only August was favorable for lake breeze development, and

 

15 of the 22 days analyzed occurred during that month.
These anomalous conditions reduced the amount of

data available for the present investigation. A longer

period of observation would greatly aid both the attempt

to determine the mean position of lake breeze fronts and

the effort to identify conditions of land—water temperature

contrast and regional wind speed which are favorable to

lake breeze development.

9.

10.

ll.

12.

CHAPTER IV——REFERENCES

Fisher, E. L. 1960. An observational study of the sea
breeze. J. Meteor. l7: 6U5—60.

 

Wexler, R. l9U6. Theory and observations of land and
sea breezes. Bull. Amer. Meteor. Soc. 27: 272—87.

 

Olsson, L. E. 1969. Lake Effects of Air Pollution
Dispersion. Univ. of Michigan, Dept. of Meteor.
and Oceanography, Tech. Rept. Ann Arbor.

 

 

Ellicott, A. 1799. Miscellaneous observations relative
to the western parts of Pennsylvania, particularly
those in the neighborhood of Lake Erie. Amer.

Philos. Soc. Trans. U: 22U—29.

 

Hazen, H. A. 1893. The Climate of Chicago. U. S.
Weather Bureau Bull. No. 10. Washington: U. S.
Weather Bureau.

 

Biggs, W. G., and Graves, M. E. 1962. A lake breeze
index. J. Appl. Meteor. l: U7U-80.

 

Pearce, R. P. 1962. A simplified theory of the genera—
tion of sea breezes. Quart. J. R. Meteor. Soc.

88: 20-29.

 

Hall, C. D. 195U. Forcasting the lake breeze and its
effects on visibility at Chicago Midway Airport.
Bull. Amer. Meteor. Soc. 35: 105-11.

 

Munn, R. E., and Richards, T. L. 196U. The lake—breeze:
a survey of the literature and some applications
to the Great Lakes. Great Lakes Res. Div. Pub.
11: 253—66.

 

Staley, D. O. 1957. The low level sea breeze of north—
west Washington. J. Meteor. lU: U58-70.

 

Fisher, E. L. 1961. A theoretical study of the sea
breeze. J. Meteor. 18: 216-33.

 

 

Estoque, M. A. 1961. A theoretical investigation of
the sea breeze. Quart. J. R. Meteor. Soc. 87:
l36-U6.

lOO

 

l3.

1U.

l5.

l6.

l7.

l8.

19.

20.

21.

22.

23.

2U.

lOl

Haurwitz, B. l9U7. Comments on the sea breeze circu—
lation. J. Meteor. U: 1—8.

 

Frizzola, J. A., and Fisher, E. L. 1963. A series of
sea breeze observations in the New York City
area. J. Appl. Meteor. 2: 722-39.

 

Estoque, M. A. 1962. The sea breeze as a function of
the prevailing synoptic situation. J. Atmos. Sci.
19: 2UU—50.

 

Moroz, W. J. 1967. A lake breeze on the eastern shore
of Lake Michigan: observations and model.
J. Atmos. Sci. 2U: 337-55.

 

Moroz, W. J., and Hewson, E. W. 1966. The mesoscale
interaction of a lake breeze and low level out—
flow from a thunderstorm. J. Appl. Meteor.

5: lU8—55.

 

 

Olsson, L. E., Cole, A. L., and Hewson, E. W. 1968.
An observational study of the lake breeze on the
eastern shore of Lake Michigan, 25 June 1965.
Proc. 11th Conf. Great Lakes Res.: 313—35.

 

Byers, H. R. 1959. General Meteorology. New York:
McGraw—Hill.

 

Malkus, J. S., Bunker, A. F., and McCasland, K. 1951.
A formation of pileus—like veil clouds over Cape
Cod, Massachusetts. Bull. Amer. Meteor. Soc.
32: 61—66.

 

Visher, S. S. l9UU. Climate of Indiana. Bloomington:
Ind. Univ. Pubs., Science Series No. 13.

 

Eshleman, C. H. 1922. Do the Great Lakes diminish
rainfall in the crop growing season? Mon. Wea.
Rev. U9:500—02.

Changnon, S. A., Jr. 1961. Precipitation contrasts
between Chicago urban area and an offshore station
in southern Lake Michigan. Bull. Amer. Meteor.
S92. U2 (1): 1—10.

 

Blust, F., and DeCooke, B. G. 1960. Comparison of
precipitation on islands of Lake Michigan with
precipitation on the perimeter of the lake.

J. Geophysical Res. 65: 1565—72.

 

Stout, G. E., and Wilk, K. E. 1962. Influence of Lake
Michigan on squall line rainfall. Great Lakes
Res. Div. Pub. 9: 111—15.

 

 

Iv'j

102

Weiss, L. W., and Kresge, R. F. 1962. Indications of
uniformity of shore and offshore precipitation
for southern Lake Michigan. J. Appl. Meteor.

l: 27l—7U.

 

Williams, G. C. 196U. Comparative rainfall study,
68th Street crib and Chicago area, summer and
fall 1963. Great Lakes Res. Div. Pub. 11:
311—20.

 

Lansing, L. 1965. Airmass modification by Lake Ontario
during the April—November period. Great Lakes
Res. Div. Pub. 13: 257—61.

 

 

Lyons, W. A., and Wilson, J. W. 1968. The Control of
Summertime Cumuli and Thunderstorms by Lake
Michigan during Non-Lake Breeze Conditions.
Satellite and Mesometeorology Research Project
Res. Pap. 7U. Chicago: Univ. of Chicago Press.

 

 

 

 

Pearson, J. E. 1958. Influence of lakes and urban
areas on radar observed precipitation echoes.
Bull. Amer. Meteor. Soc. 39: 79—82.

 

Changnon, S. A., Jr. 1966. Effect of Lake Michigan
on severe weather. Great Lakes Res. Div. Pub.
15: 220-3U.

 

Lyons, W. A. 1966. Some effects of Lake Michigan
upon squall lines and summertime convection.
Great Lakes Res. Div. Pub. 15: 259—73.

 

Altas, D. 1960. Radar detection of the sea breeze.
J. Meteor. l7: 2UU—58.

 

Leopold, L. B. l9U9. The interaction of Trade Wind
and sea breeze, Hawaii. J. Meteor. 6: 312—30.

 

Byers, H. R., and Rodebush, H. R. 19U8. Causes of
thunderstorms of the Florida peninsula. J. Meteor.

5: 275—80.

 

Fujita, T. and others. 1963. Cloud distribution over
the Great Lakes region as observed by TIROS
meteorological satellite (Abst.). Bull. Amer.
Meteor. Soc. UU: 70U.

 

 

Shenfield, L., and Thompson, F. D. 1962. The thunder—
storm of August 9, 1961, at Hamilton, Ontario.
Tech. Rpt. U17, Meteor. Branch, Dept. of Transp.,
Canada.

 

38.

39.

U0.

U1.

U2.

U3.

UU.

U5.

U6.

U7.

U8.

U9.

103

Schaefer, V. J. 1969. The inadvertent modification of
the atmosphere by air pollution. Bull. Amer.
Meteor. Soc. 50: 199—206.

 

 

Changnon, S. A., Jr. 1968. Precipitation from thunder~
storms and snowfall around southern Lake Michigan.
Proc. 11th Conf. Great Lakes Res.: 285—97.

 

Schroeder, M. J. and others. 1967. Marine air invasion
of the Pacific coast: a problem analysis. Bull.
Amer. Meteor. Soc. U8: 802—03.

 

Baralt, G. L., and Brown, R. A. 1965. The Land and
Sea Breeze: An Annotated Bibliography. Satellite
and Mesometeorology Research Project. Chicago:
Univ. of Chicago Press.

 

 

Changnon, S. A., Jr. 1968. The La Porte weather anom—
aly——fact or fiction? Bull. Amer. Meteor. Soc.
U9: U—ll.

 

Visher, S. S. 1935. Indiana regional contrasts in
temperature and precipitation with special at-
tention to the length of the growing season and
to non—average temperatures and rainfalls. Proc.
Ind. Acad. Sci. U5: l83—20U.

 

Brunnschweiler, D. 1962. Precipitation regime in
the Lower Peninsula of Michigan. Paps. Mich.
Acad. Sci. Arts Letters U7: 367—81.

 

 

Ogden, T. L. 1969. The effect on rainfall of a large
steelworks. J. Appl. Meteor. 8:585-91.

 

Hodgins, L. E. 1960. Genetic Climatology of the Great
Lakes. East Lansing: Michigan St. Univ., M. A.
Thesis.

 

U. S. Weather Bureau. 1969. Local Climatological
Data. Chicago, Ill.; June, July, and August.

 

McFadden, J. D., and Ragotzkie, R. A. 1963. Aerial
mapping of surface temperature patterns of Lake
Michigan. Great Lakes Res. Div. Pub. 10: 55-58.

 

Wagner, A. J. 1969. The weather and circulation of
June 1969: A predominantly cool and wet month.
Mon. Wea. Rev. 97: 68U-90.

 

lOU

50. Andrews, J. F. 1969. The weather and circulation of
July 1969: A predominantly wet month, cool in
the north and warm in the south. Mon. Wea. Rev.
97: 735-38.

 

51. Dickson, R. R. 1969. The weather and circulation of
August 1969: a month of record warmth in the
west. Mon. Wea. Rev. 97: 830-3U.

 

CHAPTER V

DISCUSSION

The results of the climatic survey reported in Chap—
ter IV suggest that during June through August of 1969, on
days when lake breezes developed on the southeastern shore
of Lake Michigan, the lake breeze front frequently penetrated
to the vicinity of La Porte. Literature has been cited
which indicates that convergence, vertical air motion, and
cloud formation can occur along the front of a lake breeze.
The role which the location of this convergence has played
in the existence of the La Porte rainfall anomaly can not
be assessed by this project. Some conjecture and discus—
sion is possible, however.

Changnon (l) believed that lake breeze development in
northwestern Indiana might assist in the overall process
resulting in the anomaly. He concluded, however, that the
addition of nuclei, heat, and moisture to the atmosphere by
the industrial complex near Gary, Indiana, was the primary
cause. His data showed that warm season precipitation at
La Porte began increasing above that of Valparaiso and South
Bend about 1925 and remained anomalously high through ap—
proximately 1960. Changnon believed that the temporal

pattern of rainfall at La Porte correlated well with that of

105

 

106

steel production by the Gary—Chicago complex over the same
period.
Ogden (2), however, believed that a 20% increase in
the average reading due to a change of gage site in 1927
could account for all precipitation changes up to l9U0.
Changes since l9U0 have been on the order of 20%, and he
observed variations of this magnitude occurring frequently
in Australia unrelated to changes in neighboring stations
or industrial activity. Holzman and Them (3) concluded that
measurement error following a change in observer and instru-
ment site in 1927 was responsible for the apparent anomaly.
The possibility must also be considered, however,
that mean macroscale climatic patterns between 1925 and
1960 were different from those before and after that period,
and that the patterns prevailing during that period somehow
favored the La Porte anomaly. Namias (U,5) found that
during the 1960's the mean position of a mid—tropospheric
long-wave trough which normally lies over the eastern United
States during the summer shifted offshore. This resulted
in-subsidence and stability over the northeastern part of
the country; it also produced below normal temperatures as
a result of an increased northerly component in upper level
winds. Wahl and Lawson (6) have suggested that the cooling
since 1960 represents a return to conditions which pre—
vailed in the late 1800's. Lamb (7) also believed that

post-1960 climatic conditions have been similar to those

 

107

of the late 19th century and noted an increase in meridional
air flow over extratropical regions. Thus there is some
evidence that the climatic regime of the eastern United
States may have undergone variations within the last 75
years which correspond temporally with the apparent emer—
gence and subsequent decline of the La Porte rainfall
anomaly.

In an effort to gain some further understanding of

climatic conditions in northwestern Indiana before, during,

 

and after the period when the La Porte anomaly was most
pronounced, Table 10 was prepared. In this table the June—
August rainfall totals for La Porte and Valparaiso are pre—
sented for each year since 1914. The difference in pre—
cipitation between the two stations is also given (positive
when La Porte's rainfall exceeds that at Valparaiso). In
addition, the mean daily maximum temperature for June through
August at La Porte and its departure from the 1931—1962
normal mean daily maximum is presented for each year. Data

for these figures were obtained from Climatological Data (8).

 

It can be seen that prior to 1930 and after 1960 mean
daily maximum temperatures were predominantly below normal;
the average departure was —l.5°F for the period 1913—1929
and -l.50F for 1961—1969. During the intervening years
positive departures were more frequent than negative de-
partures, with the average being +0.20. These findings

are in agreement with those of the studies mentioned above

108

TABLE 10.—-Summer Precipitation and Temperature Data for
La Porte and Valparaiso, 1914-1969.

 

June-August June—August

 

 

 

Year Precipitation, Inches Temperature, 0F
La Porte Valparaiso Difference Mean Departure
Maximum from normal*

1969 11.37 11.33 + .04 82.3 -1.9
1968 11.99 15.86 — 4.87 84.3 +0.1
1967 10.53 12.61 — 2.08 81.6 -2.6
1966 13.37 9.11 + 3.26 84.2 0.0
1965 9.21 10.58 — 1.37 81.6 —2.6
1964 11.05 8.88 + 2.17 83.4 —0.8
1963 10.42 11.89 — 1.47 82.7 -1.5
1962 10.22 8.22 + 2.00 82.4 —1.8
1961 13.83 13.24 + 0.59 82.0 -2.2
1960 14.94 11.61 + 3.33 —— —-
1959 17.88 11.04 + 6.84 86.2 +2.0
1958 27.79 16.63 + 1.16 80.1 —4.1
1957 14.98 16.87 - 1.89 83.4 —0.8
1956 10.28 9.03 + 1.25 84.6 +0.4
1955 15.47 12.58 + 2.89 86.1 +1.9
1954 19.76 15.36 + 4.40 83.9 —0.3
1953 10.81 9.86 + 0.95 86.6 +2.4
1952 14.55 9.69 + 4.86 85.5 +1.3
1951 10.38 14.36 — 3.98 79.8 —4.4
1950 21.17 14.59 + 6.58 —— -—
1949 10.62 8.64 + 1.98 85.8 +1.6
1948 12.01 4.93 + 7.08 82.9 -1.3
1947 13.45 8.26 + 5.19 83.7 -0.5
1946 12.38 15.10 — 2.72 83.0 —1.2
1945 20.22 12.16 + 8.06 80.6 —3.6
1944 9.82 6.90 + 2.92 86.7 +2.5
1943 20.19 15.07 + 5.12 86.0 +1.8
1942 16.12 10.11 + 6.01 82.6 —1.6
1941 12.96 11.60 + 1.36 84.3 +0.1
1940 13.34 10.30 + 3.04 84. -0.2
1939 18.84 12.79 + 6.05 83.5 —0.7
1938 22.72 14.94 + 7.78 82.3 —1.9
1937 11.27 10.93 + 0.34 82.9 —1.3
1936 8.79 7.46 + 1.33 88.6 +4.4
1935 10.60 10.44 + 0.16 82.8 —1.4

109

TABLE 10.——Continued

 

 

June-August
Precipitation, Inches

June-August
Temperature, OF

 

 

 

Year
La Porte Valparaiso Difference Mean Departure
Maximum from normal*

1934 9.03 .18 - 0.15 89.1 +4.9
1933 9.21 .29 + 0.92 87.4 +3.2
1932 13.43 .06 — 2.63 84.6 +0.4
1931 12.11 .71 + 2.40 85.4 +1.2
1930 8.02 .49 + 1.53 84.4 +0.2
1929 14.12 .28 + 3.84 81.2 —3.0
1928 11.14 .30 — 1.16 79.9 -4.3
1927 11.31 .35 — 0.04 76.7 -7.3
1926 12.03 .02 — 1.99 83.3 -0.9
1925 10.32 .94 + 2.38 86.0 +1.8
1924 12.48 .45 — 2.97 82.0 -2.2
1923 15.65 .94 — 0.29 83.9 -0.3
1922 5.07 .67 + 0.40 82.5 —1.7
1921 8.51 .44 + 0.07 87.1 +2.9
1920 —- .18 -— -— -—
1919 —- .73 —- —— —-
1918 6.49 .63 1.1a 83.3 —0.9
1917 —— .96 —- —- ——
1916 10.52 .21 0.31 84.8 +0.6
1915 11.89 .10 2.21 77.1 —7.1
1914 9.37 -- 85.9 +1.7

 

August (1950 and 1960 data missing).

*Based on 1931—1962 mean daily maximum for June—

110

and suggest that more very warm days occurred between 1930
and 1960 than before or after that period. Since daily
maximum temperature is one important factor in determining
whether a lake breeze develops, these data might suggest
that lake breezes could have been more frequent during the
1930—1960 period.

A general correspondence between the La Porte-
Valparaiso precipitation difference and the mean maximum
temperature departure at La Porte can be seen in Table 10.
During the predominantly below normal periods 1913—1929
and 1961-1969, the June—August precipitation contrast be-
tween the two stations averaged -0.23 inches and —0.19
inches, respectively. From 1930 through 1960, when summer
mean maximum temperatures were more frequently above normal,
the average precipitation difference was +2.97 inches. The
relationship between temperature departure and precipita—
tion difference for individual years is not marked; in 29
of 49 years the two variables had the same sign. This
fact would not be surprising, however, even assuming that
lake breezes were more frequent during the period in which
the La Porte anomaly was most pronounced. Maximum temper—
ature is only one of several variables which determine
whether a lake breeze will develop on a given day. Further—
more, the June—August mean maximum temperature is too coarse
a measurement to yield a high degree of correlation. Even

in the coolest years there presumably were days conducive

111

to lake breeze development, and only one or two such days
might be required if other conditions were favorable to
produce a positive rainfa11 anomaly at La Porte. It would
be expected, however, that over a period of years cool mean
maximum temperatures would reduce the probability that such
favorable days would occur, while higher temperatures would
increase that probability. The climate of northwestern
Indiana during the 1930—1960 period differed from that of

preceding and subsequent years in general temperature regime

 

as well as in the development of the La Porte anomaly.

W”

This fact suggests that the La Porte anomaly could have
been favored in some way by other climatic characteristics
which existed during those years.

In order to determine whether the La Porte anomaly
appears to be associated with particular upper level cir-
culation patterns, eight specific years were selected for
consideration; a detailed examination of such an associa-
tion is beyong the scope of this research, however. In
five of these years, 1939, 1945, 1947, 1948, and 1958,
the La Porte anomaly was strongly developed during June—
August; in the remaining three years, 1961, 1966, and 1967,
the anomaly was not evident. For each of the three summer
months in these years La Porte and Valparaiso precipitation

values were obtained from Climatological Data (8) and mean

 

upper level circulation was determined from Monthly Weather

 

Review (9) or Climatological Data-National Summary (10).

 

112

In eight of the 23 months examined (no upper level
charts were available for July, 1939), rainfall at La Porte
exceeded that at Valparaiso by two inches or more; in the
other 15 months precipitation at the two stations differed
by less than two inches. For seven of those eight months
in which the anomaly was pronounced, charts indicated that
northwestern Indiana was overlain by a mean upper—level
trough or the eastern edge of a trough. In such locations
divergence aloft generally favors atmospheric instability
and precipitation. 0n the other hand, during 12 of the 15
months when the anomaly was not evident the study area was
in the mean overlain by the center or eastern limb of an
upper level ridge. In this situation, convergence aloft
favors stable atmospheric conditions and reduced precipi-
tation. It is interesting to note that this association
on a monthly basis between upper level conditions and the
La Porte anomaly is similar to the longer—term (pre—and post—
1960) association of upper level patterns as described by
Namias (4,5) and the strength of the anomaly. This preliminary
investigation suggests that the apparent circulation changes
which have occurred since 1960 and perhaps prior to 1930
may have had a strong influence on the occurrence of the
La Porte anomaly.

In summary, it appears that the mean summer pattern
of upper level circulation over the eastern United States

during the years when the La Porte anomaly was most

 

113

pronounced, approximately 1930—1960, was different from that
which prevailed in the late 1800's and which has predominated
since 1960. Furthermore, the post-1960 pattern is similar

to that which prevailed on a monthly basis when the La Porte
anomaly did not develop during the period 1930—1960. Thus

it appears that upper level conditions may play a major

role in controlling the La Porte anomaly.

The significance of these findings in terms of the
hypothesis of this project that lake breeze convergence is
related to the La Porte anomaly is uncertain. It is pos—
sible that stable atmospheric conditions, favored beneath
and near the eastern margin of upper level ridges, reduce
the likelihood that convergence along a lake breeze front
will produce precipitation. The forced vertical air move—
ment in the convergence zone might not be sufficient to
overcome the stability and trigger the convection required
to result in rainfall. If the increased prevalence in
summer of mid—tropospheric ridges over the eastern United
States since 1960, reported by Namias, in fact represents
a return to a pattern that prevailed in the late 1800's,
then it may be that the period 1930-1960, when the La Porte
anomaly was prounounced, was an interval of more frequent
and general atmospheric instability associated with a re—
arrangement of the mean long waves. Such conditions could
have favored precipitation along lake breeze fronts. It is

also possible, however, that the degree of atmospheric

 

114

stability would affect the impact of industrial pollution
on convection and precipitation in the same way. The in-
dustrial influence might be able to initiate or intensify
convection and increase rainfall under naturally unstable
conditions, but might have little effect when stability
prevails.

Two findings reported by Changnon (l) are of parti—
cular interest here. First, during the period 1951—1964,
48% of the days when thunderstorms were reported at La Porte
but not at neighboring stations occurred when very flat
regional pressure gradients existed; only 15% occurred when
gradients were steep. In order for a lake breeze to develop,
the land—water pressure differential near the surface must
overcome the effect of any regional gradient; therefore
days with weak pressure gradients favor lake breeze devel—
opment. Second, the number of thunderstorms reported at
Ogden Dunes from 1949 to 1965, although less than at La
Porte, was higher than at other surrounding stations.
Changnon cited this as further evidence of the probable
importance of industrial pollution west of these two sites.
Figure 16, however, suggests that, with winds from westerly
azimuths, a lake breeze front frequently crosses the shore
near Ogden Dunes. Thus this station may also be near the
mean convergence zone location.

The findings detailed in Chapter III may be relevant

to a recent study of the plant geography of the sand dunes

 

115

along the southeastern shore of Lake Michigan. Harman (11)
described a forest gradient along the dunes from a more
mesophytic association of species in southwestern Michigan
to a more xerophytic one in Porter County, Indiana. He
hypothesized that summer drought in the region was especi—
ally pronounced under southwesterly surface flow associated
with a mid—continent upper level ridge. Further, he pro—
posed that when such conditions prevailed, lake breeze flow
would be more frequent along the Michigan shore than along
the shore of Indiana. The presumably cooler, more humid
lake air, Harman believed, could reduce the severity of sum—
mer drought sufficiently to enable mesophytic species to
survive on the shore more frequently subjected to its in—
fluence. The present study (see Figure 17) lends support
to Harman's hypothesis regarding lake breeze penetration.
For those days of southwesterly regional flow the frequency
of lake breeze occurrence declined rapidly southwest of
Michigan City. At Ogden Dunes, lake breezes occurred only
one—fourth as often as at Michigan City. Thus lake breeze
flow does appear to be considerably more common in northern
La Porte County and southwestern Michigan than in Porter
County.

The research method of employing wind data collected
at several stations to analyze lake breeze flow patterns
was found to be very useful. Except for the station far—

thest from Lake Michigan, Wanatah, it was generally not

 

116

difficult to determine whether a station experienced lake
breeze flow at a given time.

The number of stations used in this study was not
sufficient to allow accurate determination of the position
of the lake breeze front at a particular time or in the
mean. Unless a researcher is able to provide his own in—
strumentation, however, a station network of greater den—
sity will not be available in northwestern Indiana in the
near future. Greater uniformity of instrument sites would
be desirable also. The instrument at Westville experienced
considerable oscillation due to deflection of air currents
by the building on which it was situated. Wind velocities
at Ogden Dunes, where the instrument tower projects only
slightly above surrounding trees, were consistently lower
than those at other stations; wind direction did not seem
to be greatly affected.

An investigation similar to that described here, ex—
tended over several lake breeze seasons and encompassing
southwestern Michigan as well as northwestern Indiana,
should greatly improve our understanding of lake breeze flow
patterns and their possible relationship with biogeographical
patterns such as that described by Harman (11). Most pre—
vious published studies of lake breeze characteristics have
been confined to examination of one or a few days. A
longer study period would allow investigation of flow under
more narrowly defined synoptic situations and would more

clearly establish mean frontal positions.

 

117

Finally, determination of the degree of relationship
between the La Porte anomaly and lake breeze convergence
will require comparison of daily wind and precipitation
patterns in the study area over a long period of time. It
seems doubtful that such investigation could be conducted
on the basis of past records, since lengthy wind records
are available for only three of the six stations utilized

in the present study.

 

4.

U1

10.

11.

CHAPTER V—-REFERENCES

Changnon, S. A., Jr. 1968. The La Porte weather anom—
aly—-fact or fiction? Bull. Amer. Meteor. Soc.
49: 4—11.

 

Ogden, T. L. 1969. The effect on rainfall of a large
steelworks. J. Appl. Meteor. 8:585—91.

 

Holzman, B. G., and Thom, H. C. S. 1970. The La Porte
precipitation anomaly. Bull. Amer. Meteor. Soc.
51: 335-37.

 

Namias, J. 1966. Nature and possible causes of the
northeastern United States drought during 1962—
1965. Mon. Wea. Rev. 94: 543-54.

 

Namias, J. 1967. Further studies of drought over
northeastern United States. Mon. Wea. Rev.

951 497-508.

 

Wahl, E. W., and Lawson, T. L. 1970. The climate of
the midnineteenth century United States compared
to the current normals. Mon. Wea. Rev. 98:

259-65.

 

Lamb, H. H. 1966. Climate in the 1960's. Geogr.
Jour. 132: l83—2l2.

U. S. Weather Bureau. 1914-1969. Climatological Data,
V01. 1-75.

 

U. s. Weather Bureau. 1939, 1945, 1947, 1948, 1958.
Regular monthly charts. Mon. Wea. Rev. 67, 73,
75, 76, 86.

 

U. S. Weather Bureau. 1961, 1966, 1967. Climatological

 

 

Data——National Summary, vol. l2, 17, 18:

 

Harman, J. R. 1970. Forest types and climatic modifi—
cation along the southeast shoreline of Lake
Michigan. Annals Assoc. Amer. Geog. 60: In press.

 

118

CHAPTER VI

SUMMARY AND CONCLUSIONS

I
The present study was undertaken to evaluate possible
phytogeographic evidence of the La Porte rainfall anomaly

(1), and to make a preliminary test of the hypothesis that

 

the anomaly is in part the result of convergence along lake

breeze fronts associated with Lake Michigan.

II

A forest composition survey was conducted within the
Valparaiso morainic area in La Porte, Porter, and Lake
Counties, Indiana during August and September, 1969. The
per cent contribution of all tree species to the canopy of
twenty—six forest stands was estimated by examination of
two one—half acre plots in each stand. Shrub species ob-
served in each stand were also recorded.

The survey indicated that an abrupt change in forest
type occurs from northeast to southwest along the Valparaiso
moraine. Stands in La Porte County and eastern Porter
County were found to be dominated by mesophytic species,

particularly Fagus grandifolia (beech) and Acer saccharum

 

 

(sugar maple); stands in western Porter and Lake Counties

119

 

”...-

~

120

were dominated by more xeric species, primarily Quercus

velutina (black oak), Quercus alba (white oak), Carya ovata

 

 

(shagbark hickory), and Carya glabra (pignut hickory).

 

The distribution of several shrub species paralleled the
change in canopy composition.

Since studies have suggested that a similar distri—
bution of forest types existed prior to major European set—
tlement of the area (2,3), it is concluded that the forest
contrast is probably the result of an environmental gra—

dient and has not been produced by cultural factors.

III

A pilot survey of soil texture, and pH was also con—
ducted within the Valparaiso morainic area. Soil samples
were collected for analysis from the B horizon and from a
depth of four feet within each surveyed forest stand. Clay
loams and silty clay loams were found to predominate at
the lower depth. Although there was considerable variation
between stands, soils of the western half of the study area
were found to have a higher percentage of clay and a lower
percentage of sand than those of the eastern half. In
general, positive correlations were found between the per
cent of selected mesophytic species in the canopy and the
percentage of sand in the soil, and negative correlations
between these species and the per cent of clay. No impor—
tant relationship between forest distribution and soil pH

was detected.

 

121

Because northwestern Indiana is a tension zone be—
tween major vegetation types, it seems possible that the
greater clay content in the western part of the study area
could, even in the absence of a long—term La Porte anomaly,
reduce readily available water capacity sufficiently to
result in the absence of the mesophytic species. There-
fore it is concluded that the forest contrast cannot be
cited as strong evidence for a long—term climatic gradient
through the area.

The forest contrast along the moraine may be the re-
sult of a complex of interacting factors. Winter snowfall
is heavy in La Porte County and decreases westward through
the study area (4); this could affect soil moisture condi-
tions during the early part of the growing season. In ad—
dition, the study area lies near the margin of the "prairie
peninsula" (5) within which precipitation—evaporation ratios
decrease, precipitation becomes more variable from year to
year, and summer drought becomes more frequent; these cli—
matic tendencies may become more pronounced westward in
northern Indiana. These factors, as well as soil textural
differences and any long—term warm—season rainfall gradient
associated with lake breeze convergence, could be collec—
tively responsible for the forest contrast.

A detailed consideration of the possible ecological
importance of fires from adjacent prairie areas on forest

distribution in the study area is beyond the scope of the

 

122

present study. Since there apparently has been little
change in the position of the forest transition since the
early 1800's, however, fires are not thought to have been

a major control.

IV

Wind data were collected at six stations in north—
western Indiana and northeastern Illinois from June 11
through August 31, 1969. Twenty-two days on which lake
breezes occurred along the southeastern shore of Lake
Michigan were identified and their wind patterns intensively
studied. Analysis of data for these days indicated that
the lake breezes frequently penetrated to the vicinity of
La Porte and that inland penetration was greater during
days of northwesterly surface flow than southwesterly flow.
Under a northwesterly flow regime, lake breezes apparently
reached La Porte on over 60% of the lake breeze days and
were detected at Wanatah, approximately 18 miles from the
lakeshore, on 18% of the days. With flow from southwesterly
azimuths, penetration to La Porte occurred on less than 40%
of the days and no lake breezes were detected at Wanatah.

Lake breeze frequency under all winds with a westerly
component was found to decrease markedly westward from
Michigan City along the southern shore of Lake Michigan.
During the study period lake breezes were about half as
fPequent at Ogden Dunes as at Michigan City. When the re—

Bional wind was from south of west, lake breezes developed

 

123

only one-fourth as often at Ogden Dunes as at the latter
station.

The technique of using wind direction data to study
lake breeze penetration was found to be very effective.
However, an accurate determination of the mean position of
the lake breeze front in northern Indiana under various
synoptic patterns will require the establishment of addi—
tional recording stations in the area as well as the exten—

sion of observation over several lake breeze seasons.

V

For thirty-seven lake breeze and non-lake breeze days
at Michigan City the mean hourly wind speed (1000—1600 EST)
at Argonne and the difference between Argonne maximum tem—
perature and Lake Michigan water temperature were deter—
mined. The days were then graphed according to the values
of these two variables. It was found that a ratio between
mean regional wind speed and land-water temperature contrast
of 2.2:1 separated lake breeze and non—lake breeze days
with 65% accuracy. The graphs also demonstrated that
stronger land water—temperature contrasts and/or weaker
regional winds were required for development of lake
breezes when the regional wind was from the southwest quad-
rant than when westerly or northwesterly winds prevailed.

Lake breeze occurrence at Ogden Dunes was examined
in the same manner. A line representing a ratio between

mean regional wind speed and land—water temperature contrast

 

124

of 2.9:1 separated lake breeze days from the non—lake breeze
days with 73% accuracy. Thus greater temperature contrasts
and/or weaker regional winds were required for lake breeze
formation at Ogden Dunes than at Michigan City. Lake
breezes were found to occur at the former station under
regional flow from south of west only when the land—water
temperature difference was very high and the regional wind
was weak.

It is believed that the accuracy of differentiation
between lake breeze and non-lake breeze days would increase
if a longer study period were employed, if wind direction
categories were more narrowly defined, if a station nearer
the locations being considered were used to represent in—
land temperature and wind conditions, and if surface lake

temperatures nearer the study area could be obtained.

VI

The La Porte anomaly was most pronounced from 1930
through 1960. Studies have suggested that the period of
greatest anomaly development may have corresponded to an
interlude in which the climate of the eastern United States
differed from that which prevailed in the 1800's and which
has prevailed since 1960 (6,7). Namias (8) found that
during the 1960's an upper—level long—wave trough fre—
quently lay off the eastern coast of the U. S. during the
summer, thus placing the Great Lakes Region east of a mid—

continent ridge. During the 1930—1960 period, the mean

 

125

summer long—wave trough position was over the eastern
United States.

Examination was made of upper—level circulation pat—
terns for eight summer months in which La Porte rainfall
exceeded that at Valparaiso by two inches or more and for
15 months in which precipitation at the two stations dif—
fered by less than two inches. During 7 of the 8 months
in which the La Porte anomaly operated, the study area lay
under or just to the east of a mean upper—level trough;
during 12 of the 15 months when the anomaly was not devel—
oped, the study area lay under an upper—level ridge. Thus
the upper air patterns which prevailed seasonally during
the 1960's when the La Porte anomaly was less operative
apparently also prevailed during the period 1930—1960 in
those months when the anomaly did not develop.

This apparent temporal association on both a longm
term and a monthly basis between the appearance and dis—
appearance of the La Porte anomaly and the prevalence of
certain upper air patterns suggests that the anomaly may
not be the result of atmospheric pollution alone.

Determination of whether the La Porte anomaly is
related causally to lake breeze convergence would require
examination on a daily basis of wind flow and precipitation
patterns in the study area over a period of several years.
It is doubtful that this can be done for past years be-
cause of the scarcity of stations for which wind records

exist .

 

U'l

CHAPTER VI-—REFERENCES

Changnon, S. A., Jr. 1968. The La Porte weather anom—
aly——fact or fiction? Bull. Amer. Meteor. Soc.
49: 4—11.

 

Potzger, J. E., and Keller, C. O. 1952. The beech line
in northwestern Indiana. Butler Univ. Bot. Stud.
10: 108—13.

 

Potzger, J. E., Potzger, M. E., and McCormick, J. 1957.
The forest primeval of Indiana as recorded in
the original U. S. land surveys and an evaluation
of previous interpretations of Indiana vegetation.
Butler Univ. Bot. Stud. 13: 95—111.

 

Schaal, L. A. 1966. Climate. In Lindsey, A. A. (ed.),
Natural Features of Indiana (Indianapolis: Ind.
Acad. Sci.): 156470.

 

Transeau, E. N. 1935. The prairie peninsula. Ecology
16: 423-37.

Wahl, E. W., and Lawson, T. L. 1970. The climate of
the midnineteenth century United States compared
to current normals. Mon. Wea. Rev. 98: 259—65.

 

Lamb, H. H. 1966. Climate in the 1960's. Geogr. Jour.
132: 183—212.

 

Namias, J. 1966. Nature and possible causes of the
northeastern United States drought during 1962—
1965. Mon. Wea. Rev. 94: 543—54.

 

126

 

 

 

LIST OF REFERENC ES

127

LIST OF REFERENCES

Atlas, D. 1960. Radar detection of the sea breeze.
J. Meteor. 17: 244—58.

 

Andrews, J. F. 1969. The weather and circulation of July
1969: a predominantly wet month, cool in the
north and warm in the south. Mon. Wea. Rev.

97: 735-38.

 

Baralt, G. L., and Brown, R. A. 1965. The Land and Sea
Breeze: An Annotated Bibliography. Satellite
and Mesometeorology Research Project. Chicago:
Univ. of Chicago Press.

 

 

Bartelli, L. J., and Peters, D. B. 1959. Integrating soil
moisture characteristics with classification
units of Illinois soils. Soil Sci. Sco. Amer.
Proc. 23: 149—51.

 

Benninghoff, W. S. 1963. The prairie peninsula as a
filter barrier. Proc. Ind. Acad. Sci. 73:
116—24.

 

Biggs, W. G., and Graves, M. E. 1962. A lake breeze index.
J. Appl. Meteor. 1: 474—80.

 

Blalock, H. M. 1960. Social Statistics. New York:
McGraw—Hill.

 

Blust, F., and DeCooke, B. G. 1960. Comparison of preci—
pitation on islands of Lake Michigan with pre-
cipitation on the perimeter of the lake. J. Geo—
physical Res. 65: 1565—72.

 

Borchert, J. R. 1950. The climate of the central North

 

 

American grassland. Annals Assoc. Amer. Geog.
40: 1—39.

Braun, E. L. 1950. Deciduous Forests of Eastern North
America. New York: Hafner.

Bretz, J. H. 1955. Geology of the Chicago region. Part II-—
the Pleistocene. Ill. St. Geol. Survey Bull.
65, Part II.

 

128

 

129

Brooks, C. F. 1915. The snowfall of the eastern United
States. Mon. Wea. Rev. 43: 2-11.

 

Brunnschweiler, D. 1962. Precipitation regime in the Lower
Peninsula of Michigan. Paps. Mich. Acad. Sci.
Arts Letters 47: 367-81.

 

 

Buckman, H. C., and Brady, N. C. 1960. The Nature and
Properties of Soils. New York: MacMillan.

 

 

Bushnell, T. M. 1918. Soil Survey of Porter County, Indiana.
Washington: Gov. Printing Office.

 

1921. Soil Survey of Lake County, Indiana.
Washington: Gov. Printing Office.

 

 

Byers, H. R. 1959. General Meteorology. New York:
McGraw—Hill.

 

 

Byers, H. R., and Rodebush, H. R. 1948. Causes of thunder—
storms of the Florida peninsula. J. Meteor.

5: 275—80.

 

Changnon, S. A., Jr. 1961. Precipitation contrasts between
Chicago urban area and an offshore station in
southern Lake Michigan. Bull. Am. Meteor. Soc.
42: 1—10.

 

1966. Effect of Lake Michigan on severe
weather. Great Lakes Res. Div. Pub. 15: 220—34.

 

 

1968. The La Porte weather anomaly——fact or

 

fiction? Bull. Amer. Meteor. Soc. 49: 4—11.

 

1968. Precipitation Climatology of Lake
Michigan Basin. Urbana: 111. St. Water Survey

 

 

 

 

Bull. 52.
1968. Precipitation from thunderstorms and
snowfall around southern Lake Michigan. Proc.

 

11th Conf. Great Lakes Res.: 285—97.

 

1970. Reply (to Holzman and Thom, 1970).
Bull. Amer. Meteor. Soc. 51: 337—42.

 

 

Conrad, V., and Pollak, L. W. 1950. Methods in Climatology.
Cambridge, Mass.: Harvard Univ. Press.

 

Correlation Legends for Porter and La Porte County Soil
Survey Reports. Personal communication from Mr.
Frank W. Sanders, Soil Conservation Service,
Indianapolis. November 18, 1969.

130

Cowles, H. C. 1901. The physiographic ecology of Chicago
and vicinity; a study of the origin, development,
and classification of plant societies. Bot. Gaz.
31: 73—108, 145—82.

1901. The Plant Societies of Chicago and

 

 

Vicinity. Geogr. Soc. of Chicago Bull. No. 2.
Chicago: Univ. of Chicago Press.

Day, P. R. 1965. Particle fractionation and particle
size analysis. In Black, C. A. (ed.), Methods
of Soil Analysis (Madison, Wis.: Amer. Soc. of
Agronomy), Part I: 545—67.

 

Dickson, R. R. 1969. The weather and circulation of
August 1969: a month of record warmth in the
west. Mon. Wea. Rev. 97: 830—34.

 

Diller, O. D. 1935. The relation of temperature and pre—
cipitation to the growth of beech in northern
Indiana. Ecology 16: 72—81.

Dole, R. M. 1928. Snow squalls in the Lake Region. Mon.
Wea. Rev. 56: 512—13.

Ellicott, A. 1799. Miscellaneous observations relative
to the western parts of Pennsylvania, particularly
those in the neighborhood of Lake Erie. Amer.
Philos. Soc. Trans. 4: 224—29.

 

Eshleman, C. H. 1922. Do the Great Lakes diminish rainfall
in the crop growing season? Mon. Wea. Rev. 49:
500—02.

 

Estoque, M. A. 1961. A theoretical investigation of the
sea breeze. Quart. J. R. Met. Soc. 87: 136—46.

 

1962. The sea breeze as a function of the
prevailing synoptic situation. J. Atmos. Sci.
19: 244—50.

 

 

Finley, D., and Potzger, J. E. 1952. Characteristics of
the original vegetation in some prairie counties
of Indiana. Butler Univ. Bot. Stud. 10: 114—18.

 

Fisher, E. L. 1960. An observational study of the sea
breeze. J. Meteor. 17: 645—60.

 

1961. A theoretical study of the sea breeze.
J. Meteor. 18: 216—33.

 

 

131

Flint, R. F., and others. 1959. Glacial Map of the United
States East of the Rocky Mountains. New York:
Geol. Soc. Amer.

 

 

Franzmeier, D. P., Whiteside, E. P., and Erickson, A. E.
1960. Relationship of texture classes of fine
earth to readily available water. Trans. 7th
Internat. Congr. Soil Sci. 1: 354—63.

 

 

Friesner, R. C. 1942. Dendrometer studies of five species
of broadleaf trees in Indiana. Butler Univ. Bot.
Stud. 5: 160—72.

 

Frizzola, J. A., and Fisher, E. L. 1963. A series of sea
breeze observations in the New York City area.
J. Appl. Met. 2: 722—39.

 

Fujita, T., Mendez, R., and Gargard, S. J. M. 1963. Cloud
distribution over the Great Lakes region as ob—
served by TIROS meteorological satellite (Abst.).
Bull. Amer. Meteor. Soc. 44: 704.

 

Fuller, G. D. 1925. The Vegetation of the Chicago Region.
Chicago: Univ. of Chicago Press.

 

Gaiser, R. N. 1952. Readily available water in forest
soils. Soil Sci. Soc. Amer. Proc. 16: 334-38.

 

Gessel, S. P., and Cole, D. W. 1958. Physical analysis of
forest soils. First North American Forest Soils
Conference, Michigan St. Univ., East Lansing, Mich.

 

 

Gleason, H. A. 1968. The New Britton and Brown Illustrated
Flora of the Northeastern United States and
Adjacent Canada. New York: Hafner.

 

 

 

Gordon, R. B.’ 1936. A preliminary vegetation map of
Indiana. Amer. Midl. Nat. 17: 866—77.

 

Guennel, G. K. 1950. History of forests in the glacial

 

Lake Chicago area. Butler Univ. Bot. Stud.
9: 140—58.
Hall, C. D. 1954. Forecasting the lake breeze and its

effects on visibility at Chicago Midway Airport.
Bull. Amer. Meteor. Soc. 35: 105—11.

 

Harlow, W. M., and Harrar, E. S. 1958. Textbook of
DendrolOfiy. New York: McGraw—Hill.

 

 

Harman, J. R. 1970. Forest types and climatic modifica—
tion along the southeast shoreline of Lake Michi-
gan. Annals Assoc. Amer. Geog. 60: In press.

 

 

132

Haurwitz, B. 1947. Comments on the sea breeze circulation.
J. Meteor. 4: 1-8.

 

Hazen, H. A. 1893. The Climate of Chicago. U. S. Weather
Bureau Bull. No. 10. Washington: U. S. Weather
Bureau.

 

Holzman, B. G., and Thom, H. C. S. 1970. The La Porte
precipitation anomaly. Bull. Amer. Meteor. Soc.

512 335-37.

 

Jamison, V. C., and Kroth, E. M. 1958. Available moisture
storage capacity in relation to textural composi—
tion and organic matter content of several
Missouri soils. Soil Sci. Soc. Amer. Proc.

22: 189-92.

 

Just, T. 1957. Postglacial vegetation of the north central
United States (Abst.). Geol. Soc. Amer. Bull.
68: 1895.

 

Kenoyer, L. A. 1933. Forest distribution in southwest
Michigan as interpreted from the original survey.
Paps. Mich. Acad. Sci. Arts Letters 19: 107-11.

 

Krumbein, W. C. 1933. Textural and lithological variations
in glacial till. Jour. Geol. 41: 382—408.

 

Kuchler, A. W. 1964. Potential Natural Vegetation of the
Conterminous United States. New York: Amer.
Geog. Soc. Spec. Pub. No. 36.

 

Lamb, H. H. 1966. Climate in the 1960's. Geogr. Jour.
132: 183-212.

 

Lansing, L. 1965. Airmass modification by Lake Ontario
during the April—November period. Great Lakes
Res. Div. Pub. 13: 257—61.

 

 

Leighly, J. 1941. Effects of the Great Lakes on the an—
nual march of air temperature in their vicinity.
Paps. Mich. Acad. Sci. Arts Letters 27: 377—414.

 

LeOpold, L. B. 1949. The interaction of Trade Wind and

 

sea breeze, Hawaii. J. Meteor. 6: 312—30.
Lindsey, A. A. 1961. Vegetation of the drainage-aeration
classes of northern Indiana soils in 1830.

Ecology 42: 432—36.

 

133

Lindsey, A. A., Crankshaw, W. B., and Quadir, S. A. 1965.
Soil relations and distribution map of the vege—
tation of presettlement Indiana. Bot. Gaz. 126:

155-63.

Lund, Z. F. 1959. Available water—holding capacity of
. alluvial soils in Louisiana. Soil Sci. Soc.
Amer. Proc. 23: 1-3.

 

 

Lyons, W. A. 1966. Some effects of Lake Michigan upon
squall lines and summertime convection. Great
Lakes Res. Div. Pub. 15: 259—73.

 

Lyons, W. A., and Wilson, J. W. 1968. The Control of
Summertime Cumuli and Thunderstorms by Lake
Michigan during Non—Lake Breeze Conditions.
Satellite and Mesometeorology Research Project
Res. Pap. 74. Chicago: Univ. of Chicago Press.

 

 

 

Malkus, J. S., Bunker, A. F., and McCasland, K. 1951.
A formation of pileus—like veil clouds over Cape

Cod, Massachusetts. Bull. Amer. Meteor. Sgg.
32: 61—66.

 

McFadden, J. D., and Ragotzkie, R. A. 1963. Aerial mapping
of surface temperature patterns of Lake Michigan.
Great Lakes Res. Div. Pub. 10: 55—58.

 

McQueeney, C. R. 1950. An ecological study of the rela—
tionship between direction of slope, elevation,
and forest cover in Brown County, Indiana.
Butler Univ. Bot. Stud. 9: 239—69.

 

Meyer, A. H. 1950. Fundament vegetation of the Calumet
Region, northwest Indiana—northeast Illinois.
Paps. Mich. Acad. Sci. Arts Letters 36: 177—82.

 

Morgan, M. D. 1969. Ecology of aspen in Gunnison County,
Colorado. Amer. Midl. Nat. 82: 204—28.

 

Moroz, W. J. 1967. A lake breeze on the eastern shore of
Lake Michigan: observations and model. J. Atmos.
Sci. 24: 337—55.

Moroz, W. J., and Hewson, E. W. 1966. The mesoscale inter—
action of a lake breeze and low level outflow
from a thunderstorm. J. Appl. Meteor. 5: 148—55.

 

Munn, R. E., and Richards, T. L. 1964. The lake—breeze:
a survey of the literature and some applications
to the Great Lakes. Great Lakes Res. Div. Pub.
11: 253—66.

 

 

134

Namias, J. 1966. Nature and possible causes of the north—
eastern United States drought during 1962-1965.
Mon. Wea. Rev. 94: 543-554.

 

. 1967. Further studies of drought over north—
eastern United States. Mon. Wea. Rev. 95: 497—

 

 

 

508.

Odell, C. B. 1931. Influence of Lake Michigan on east
and west shore climates. Mon. Wea. Rev. 59:
405—10.

Ogden, T. L. 1969. The effect on rainfall of a large
steelworks. J. Appl. Meteor. 8: 585—91.

 

Olmstead, C. W. 1956. American orchard and vineyard
regions. Econ. Geogr. 32: 189—236.

 

Olsson, L. E. 1969. Lake Effects on Air Pollution Dis—
persion. Univ. of Michigan, Dept. of Meteor.
and Oceanography, Tech. Rept. Ann Arbor.

 

 

Olsson, L. E., Cole, A. L., and Hewson, E. W. An observa—
tional study of the lake breeze on the eastern
shore of Lake Michigan, 25 June 1965. Proc. 11th
Conf. Great Lakes Res.: 313—25.

 

 

Pearce, R. P. 1962. A simplified theory of the generation
of sea breezes. Quart. J. R. Met. Soc. 88: 20—29.

 

Pearson, J. E. 1958. Influence of lakes and urban areas
on radar observed precipitation echoes. Bull.
Amer. Meteor. Soc. 39: 79—82.

 

Petersen, G. W., Cunningham, R. L., and Matelski, R. P.
Moisture characteristics of Pennsylvania soils:
I. Moisture retention as related to texture.
Soil Sci. Soc. Amer. Proc. 32: 271—75.

 

Petty, R. C., and Jackson, M. T. 1966. Plant communities.
In Lindsey, A. A. (ed.), Natural Features of
Indiana (Indianapolis: Ind. Acad. Sci.): 264—96.

 

Potzger, J. E. 1935. Topography and forest types in a

 

central Indiana region. Amer. Midl. Nat. 16:
212—29.
1946. Phytosociology of the primeval forest

 

in central—northern Wisconsin and Upper Michigan,
and a brief post—glacial history of the lake
forest formation. Ecol. Monogr. 16: 211—50.

 

135

Potzger, J. E., and Friesner, R. C. 1939. Plant migra—
tions in the southern limits of Wisconsin gla—
ciation in Indiana. Amer. Midl. Nat. 22: 351—68.

 

1940. What is climax in central Indiana?
A five—mile quadrat study. Butler Univ. Bot.
Stud. 4: 181—95.

 

 

 

Potzger, J. E., and Keller, C. O. 1952. The beech line in
northwestern Indiana. Butler Univ. Bot. Stud.
10: 108—13.

 

Potzger, J. E., Potzger, M. E., and McCormick, J. 1957.
The forest primeval of Indiana as recorded in
the original U. S. land surveys and an evaluation
of previous interpretations of Indiana vege-
tation. Butler Univ. Bot. Stud. 13: 95—111.

 

,Quick, B. E. 1923. A comparative study of the distribu—
tion of the climax association in southern
Michigan. Paps. Mich. Acad. Sci. Arts Letters
3: 211—44.

 

Rohr, F. W., and Potzger, J. E. 1950. Forest and prairie
in three northwestern Indiana counties. Butler
Univ. Bot. Stud. 10: 61—70.

 

Schaal, L. A. 1966. Climate. In Lindsey, A. A. (ed.),
Natural Features of Indiana. (Indianapolis:
Ind. Acad. Sci.): 156:70.

 

Schaefer, V. J. 1969. The inadvertent modification of
the atmosphere by air pollution. Bull. Amer.
Meteor. Soc. 50: 199—206.

 

 

Schneider, A. F. 1966. Physiography. In Lindsey, A. A.
(ed.), Natural Features of Indiana (Indianapolis:
Ind. Acad. Sci.): 40—56.

 

. 1967. The Tinley Moraine in Indiana. Proc.
Ind. Acad. Sci. 77: 271-78.

 

 

Schroeder, M. J. and others. 1967. Marine air invasion
of the Pacific coast: a problem analysis. Bull.
Amer. Meteor. Soc. 48: 802—08.

 

Sears, P. B. 1948. Forest sequence and climatic change
in northeastern North America since early Wis—
consin time. Ecology 29: 326—33.

 

Shelford, V. E. 1963. The Ecology of North America.
Urbana: Univ. of 111. Press

 

136

Shenfield, L., and Thompson, F. D. 1962. The thunder—
storm of August 9th, 1961, at Hamilton, Ontario.
Tech. Rpt. 417, Meteor. Branch, Dept. of Transp.,
Canada.

 

Shreve, F. 1917. A map of the vegetation of the United
States. Geog. Rev. 3: 119-25.

 

Soils of the North Central Region of the United States.
North Central Region Pub. No. 76} Madison:
Univ. of Wis. Agric. Exp. Station.

 

Spurr, S. H. 1964. Forest Ecology. New York: Ronald
Press.

 

Staley, D. C. 1957. The low level sea breeze of northwest
Washington. J. Meteor. 14: 458-70.

 

Stout, G. E., and Wilk, K. E. 1962. Influence of Lake
Michigan on squall line rainfall. Great Lakes
Res. Div. Pub. 9: 111—115.

 

 

 

Thomas, M. K. 1964. A survey of Great Lakes snowfall.
Great Lakes Res. Div. Pub. 11: 294—310.

 

Transeau, E. N. 1905. Forest centers of eastern America.
Amer. Naturalist 39: 875—89.

 

. 1935. The prairie peninsula. Ecology 16:
423-37.

 

Trewartha, G. T. 1961. The Earth's Problem Climates.
Madison: Univ. of Wis. Press.

 

1968. An Introduction to Climate. New York:
McGraw—Hill.

 

 

Ulrich, H. P. and others. 1944. Soil Survey: La Porte

 

 

County, Indiana. Washington: Gov. Printing
Office.
U. S. Soil Conservation Service. 1967. Lake County Soil—

 

Survey Maps. Unpublished.

 

U. S. Weather Bureau. 1914-1969. Climatological Data,

 

 

 

vols. 1—75.
1968. Climatological Data—Annual Summagy,
vol. 74.

1961, 1966, 1967. Climatological Data—
National Summary, vols. 12, l7, l8.

 

 

 

137

U. S. Weather Bureau. 1969. Daily Weather Map. All dates
from June 11 through August 31.

 

. 1969. Local Climatological Data. Chicago:
June, July, and August.

 

 

1939, 1945, 1947, 1948, 1958. Regular monthly
charts. Mon. Wea. Rev. 67, 73, 75, 76, 86.

 

Visher, S. S. 1935. Indiana regional contrasts in temper-
ature and precipitation with special attention to
the length of the growing season and to non—
average temperatures and rainfalls. Proc. Ind.
Acad. Sci. 45: l83-204.

 

 

1943. Some climatic influences of the Great
Lakes, latitude, and mountains; an analysis of
climatic charts in "Climate and Man," 1941.
Bull. Amer. Meteor. Soc. 24: 205—10.

 

 

1944. Climate of Indiana. Bloomington: Ind.
Univ. Pubs., Science Series No. 13.

 

 

Wagner, A. J. 1969. The weather and circulation of June
1969: A predominantly cool and wet month. Mon.
Wea. Rev. 97: 684—90.

Wahl, E. W., and Lawson, T. L. 1970. The climate of the
midnineteenth century United States compared to
the current normals. Mon. Wea. Rev. 98: 259—65.

 

Ward, R. T. 1956. The beech forests of Wisconsin——
changes in forest composition and the nature of
the beech border. Ecology 37: 407—19.

Wayne, W. J. 1956. Thickness of Drift and Bedrock Physio—
graphy of Indiana North of the Wisconsin Glacial
Boundary. Bloomington: Ind. Dept. of Conserva—
tion, Geol. Survey, Rept. of Progress No. 7.

Wayne, W. J., and Zumberge, J. H. 1965. Pleistocene
geology of Indiana and Michigan. In Wright, J. E.
and Frey, D. G. (eds.), The Quaternary of the
United States (Princeton, N. J.: Princeton Univ.

Press): 63—83.

 

 

Weiss, L. W., and Kresge, R. F. 1962. Indications of uni-
formity of shore and offshore precipitation for
southern Lake Michigan. J. Appl. Meteor. 1:
271-74.

 

 

Wenner, K.

Wexler, R.

Whittaker,

Williams,

Zumberge,

138

, and Persinger, I. 1967. Lake County Interim
Soil Survey Report. Unpublished.

 

 

1946. Theory and observations of land and sea
breezes. Bull. Amer. Meteor. Soc. 27: 272—87.

 

R. H. 1956. Vegetation of the Great Smoky
Mountains. Ecol. Monogr. 26: 1-80.

G. C. 1964. Comparative rainfall study, 68th
street crib and Chicago area, summer and fall
1963. Great Lakes Res. Div. Pub. 11: 311—20.

J. H. and Potzger, J. E. 1956. Late Wisconsin
chronology of the Lake Michigan basis correlated
with pollen studies. Geol. Soc. Amer. Bull.

67: 271—88.

 

 

 

APPENDICES

139

APPENDIX I

LOCATIONS OF SURVEYED FOREST STANDS

 

Stand County Congressional Road
No. Land
Description

1 La Porte Sec. 20 T38N,R1W NE side Emergy W of 750E

2 La Porte Sec. 16 T37N,R1W NE corner 350N—850E

3 La Porte Sec. 15 T37N,R2W SW corner 600N—150E

4 La Porte Sec. 20 T37N,R3W S side 300N near 400W

5 La Porte Sec. 19 T37N,R3W W side 500W S of Johnson

6 La Porte Sec. 16 T36W,R4W N side 2508

7 La Porte Sec. 20 T36N,R4W E side llOOW

8 La Porte Sec. 18 T36N,R4W N side 3008

9 Porter Sec. 36 T36N,R6W S side 700N E of 625E
10 Porter Sec. 16 T35N,R5W W side of 325E % mi. N of 300N
11 Porter Sec. 4 T35N,R5W E side of 300E
12 Porter Sec. 5 T35N,R5W N side of 500N
13 Porter Sec. 18 T35N,R5W S side of 4OON % mi. W of 200E
14 Porter Sec. 7 T35N,R5W E side Rt. 49 S of 450N
15 Porter Sec. 2 T35N,R6W NE corner 550N — 50W
16 Porter Sec. 26 T36N,R6W SW corner Meridian Rd.—U.S.6
17 Porter Sec. 4 T34N,R6W W side Rt. 2
18 Porter Sec. 7 T34N,R6W E Side 500W N Of C80 tracks
19 Porter Sec. 19 T35N,R6W S Side U.S.3O
20 Porter Sec. 34 T35N,R7W N side Division Rd.
21 Lake Sec. 19 T34N,R7W E side Gibson N of 129th

22 Lake Sec. 11 T33N,R8W W side Colorado near 157th
23 Lake Sec. 30 T35N,R8W N Side 918t E Of Whitcomb

24 Lake Sec. 36 T34N,R9W W Side Clark

2 Lake Sec. 29 T34N,R9W S side Brunswick

26 Lake Sec. 5 T33N,R9W S side 151st W of Magoun

 

140

 

APPENDIX II

TOTAL NUMBER OF ARBOREAL STEMS

SURVEYED IN EACH STAND*

 

 

 

Stand Number Number of Stems
1 118
2 83
3 202
4 148
5 139
6 204
7 155
8 111
9 152

10 92
11 184
12 130
13 150
14 98
15 80
16 71
17 99
18 106
19 82
20 89
21 82
22 64
23 108
24 101
25 163
26 100

*Data in this Appendix can be used in conjunction
with Table l to determine absolute densities (per acre)
of individual species.

141

APPENDIX III

PER CENT SAND, SILT, AND CLAY FOR

INDIVIDUAL SOIL SAMPLES

B Horizon

 

Four-Foot Depth

 

 

Stand No.

Sand Silt Clay Sand Silt Clay
1 27.8 42.5 29.7 62.5 22.0 15.5
17.4 44.4 38.2 21.3 47.7 31.0

2 21.4 52.7 25.9 15.1 56.0 28.9
82.3 11.7 6.0 72.1 16.9 11.0
3 91.0 5.9 3.1 95.8 0.9 3.3
67.3 29.6 3.1 92.5 5.2 2.3

4* 46.0 29.8 24.2 47.2 23.9 28.9
41.4 31.5 27.1 —— —— ——

5 38.7 43.2 18.1 38.5 33.1 28.4
42.2 38.2 19.3 46.2 29.7 24.1

6 6.8 57.1 36.1 20.3 49.7 30.0
15.5 48.6 35.9 21.1 49.8 29.1

7 25.3 43.2 31.3 19.3 41.7 39.0
21.5 47.2 31.3 17.7 55.3 27.0

8 24.3 42.8 26.9 38.9 32.5 28.6
28.4 45.7 25.9 63.7 17.8 18.5

9 25.8 46.6 27.6 19.6 40.7 39.7
15.2 51.4 33.4 15.0 52.2 32.8

10 32.9 39.4 27.7 45.0 34.2 20.8
21.6 39.0 39.4 25.1 41.5 33.4

11 58.5 15.9 25.6 29.4 38.7 31.9
44.1 34.5 21.4 23.6 49.1 27.3

12 24.2 44.4 31.4 26.6 41.6 31.8
32.2 43.6 24.0 18.7 42.5 38.8

13 36.3 36.1 27.6 34.7 42.0 23.3
33.1 40.3 26.6 36.8 37.3 25.9

142

 

 

143

Appendix III——Continued

 

 

 

 

 

Stand No. B Horizon Four—Foot Depth

Sand Silt Clay Sand Silt Clay

14 28.0 47.5 24.5 23.2 50.6 26.2
13.7 48.5 37.8 28.8 43.3 27.9

15 14.7 51.7 33.6 14.7 51.4 33.9
17.8 49.2 33.0 14.0 54.0 32.0

16 17.4 48.8 33.8 18.2 55.8 26.0
18.1 46.8 35.1 23.0 51.0 26.0

17 27.1 43.1 29.8 30.5 37.4 32.1
23.8 39.7 36.5 29.0 44.6 26.4

18 15.9 41.9 42.2 25.0 48.8 26.2
17.4 41.0 41.6 27.5 43.5 29.0

19 20.7 45.1 34.2 27.1 44.7 28.2
57.4 28.0 14.6 88.0 4.6 7.4

20 10.6 47.1 42.3 14.2 57.3 28.5
11.9 49.7 38.4 14.9 58.1 27.0

21 30.0 28.7 41.3 16.9 51.5 31.6
12.1 48.9 39.0 15.2 50.4 34.4

22 14.3 43.0 42.7 15.8 51.1 33.1
16.1 39.5 44.4 60.2 20.3 19.5

23 3.4 47.9 48.7 5.9 63.8 30.3
1.1 46.9 52.0 2.1 59.9 38.0

24 11.9 34.3 53.8 12.2 46.9 40.9
14.1 39.5 46.4 14.9 45.0 40.1

25 2.6 37.4 60.0 21.3 49.8 28.9
5.4 31.9 62.7 5.2 43.0 51.8

26 26.4 34.5 39.1 13.9 50.9 35-2
22.6 37.3 40.1 31.9 37.0 31.1

 

*Only one sample taken from four feet due to nearly
impenetrable gravel at a depth of about two feet.

 

APPENDIX IV

VALUES OF pH FOR INDIVIDUAL SOIL SAMPLES

 

 

 

Stand No. B Horizon Four—Foot Depth
1 4.65 4.68
4.64 7.79
2 4.20 5.88
5.11 5.30
3 5.39 ' 6.06
4.90 5.42
4 4.90 4.25
4.53 __
5 4.69 4.43
4.78 4.72
6 4.20 7.72
4.46 7.99
7 5.46 5.11
4.40 5.09
8 4.50 4.88
4.25 5.98
9 4.45 6.24
4.41 7.23
10 4.29 4.96
4.60 7.49
11 4.10 4.48
4.17 7.62
12 4.46 5.41
4.51 7.59
13 4.62 7.62
5.05 7.20
144

145

Appendix IV——Continued

 

 

 

 

Stand No. B Horizon Four—Foot Depth
14 4.76 7.84
4.30 7.70
15 4.14 7.54
4.41 7.58
16 6.41 7.64
5.41 7.78
17 4.59 5.14
4.38 7.70
18 4.10 7.84
4.39 7.12
19 4.40 5.21
5.30 4.72
20 4.08 7.63
4.77 7.69
21 4.42 7.91
4.15 7.68
22 4.49 7.61
4.13 6.83
23 5.15 7.92
5.49 7.81
24 4.29 7.81
4.22 7.84
25 4.20 7.71
4.38 7.80
26 4.21 6.59
4.24 7.70

 

 

APPENDIX V

LAKE BREEZE AND NON—LAKE BREEZE DAYS AT
MICHIGAN CITY AND OGDEN DUNES,

INDIANA, EXAMINED IN CHAPTER IV

Michigan City:

 

Twenty—two lake breeze days: June 28
July 10, 12, 14, 23, 25, 30
August 1, 2, 4, 5, 8, ll, l2,
17, 18, 24, 25, 27—30

 

Fifteen non—lake breeze days: June 16, 26
July 2, 4, 9, 11, 15, 16,
28., 31
August 6, 7, 10, 13, 31

Ogden Dunes:

 

Thirteen lake breeze days: June 28
July 10, 12, 14
August 1, 2, 4, 8, 11, 12,
24, 25, 27

Twenty-four non—lake
breeze days: All other days listed for
Michigan City

 

146

 

 

 

* "I11411441111I