Previous climatological studies of low-level jets (LLJs) have been restricted to individual geographic regions. In this study, an expanded climatology of the characteristics of northerly low-level jets (N-LLJs) and southerly low-level jets (S-LLJs) is provided for North America and nearby coastal areas to better document the spatial variations of these important mesoscale circulation features. In addition, time of initiation and persistence of S-LLJ events in central North America and over the Gulf of Mexico are analyzed. The North American Regional Reanalysis (NARR), with a 32-km horizontal resolution and a 3-hourly temporal resolution, was used to analyze (by time of day, month, season and year) the frequency, height above ground level, and wind speed of LLJs, and, for S-LLJs in central North America only, diurnal and seasonal variations in the time of initiation and duration jet events. The spatial analyses highlight well-known wind maxima but also point to previously-unknown locations that experience frequent jet-like wind maxima. The analyses also suggest that boundary-layer forcing is important for S-LLJ occurrence, including S-LLJs that form at high latitudes in summer and those that form in the central and southern plains in winter. The NARR-derived analyses supplement and enhance the understanding of the climatological characteristics of low-level wind maxima across North America and coastal environs. The findings also highlight that many aspects of low-level wind maxima remain incompletely understood and point to the need for considerable further research on the processes contributing to jet formation.
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