The agricultural productions in the central and eastern United States are sensitive to springtime freeze events. As a result of global warming, increasing temperatures have led to earlier shifted springs, usually called false springs, which have resulted in disastrous damage on premature plants exposed to subsequent freeze events. This study analyzes the climatology of springtime freezes and their impacts on agriculture in the Midwestern United States for the period of 1981-2018. The study began by evaluating two potential datasets for the purpose of this analysis: the PRISM (Parameter- elevation Regressions on Independent Slopes Model, http://prism.oregonstate.edu) analysis and the ERA5 (the fifth major global reanalysis produced by European Centre for Medium-Range Weather Forecasts, Hersbach et al., 2018) reanalysis. The PRISM data are found to be a better representation of the observed freezing events and therefore used for establishing freeze events climatology, while the ERA5 reanalysis is used to understand the weather conditions and climate background of the freeze events. Freezing days in March show a decreasing trend across our study region from 1981 to 2018. EOF analysis of freezing days in March shows a relatively larger variation in the Ohio Valley, and the first EOF time series shows substantial interannual variability. The positive phase of NAO (North Atlantic Oscillation) is usually associated with less freezing risk in March across the study region. A crop yield simulation model is used to investigate the historical impacts of false springs and subsequent freeze events on fruit crop yields using apple as an example. Damage tends to occur at the early growing stages of apples when they are more vulnerable. Damage is generally occurring on earlier and warmer days, which could be due to the more frequent false spring occurrences. The Upper Midwest and the Northeast are regions that are less vulnerable to freeze damage.
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