Midwestern Snow Swaths: Empirical Observations of the Influence of Fresh Snow Cover on Temperature

The ability for fresh snow to suppress the temperature of the lower atmosphere is well known. This study examines the synoptic characteristics and atmospheric influences of specific snow events occurring during 1990’s decade in the Midwest U.S. A combination of Advanced Very High Resolution Radiometer (AVHRR) satellite data and climatological snow cover data are used to identify snow events. To maximize spatial coverage of station observations the new National Climate Data Center TD 3200/3210 data set is used. This data set combines official National Weather Service observations with those from cooperative sites. Snow “stripes” produced by the passages of mid-latitude cyclones through the study area are identified and analyzed. ERSI ArcView and ESRI/ERDAS Image Analyst is used to georeference all images and to verify the boundaries of snow coverage. The morphological characteristics of these features and their association with synoptic conditions are summarized. The snow cover effects on temperature are determined by comparing daily maximum and minimum temperatures in the snow areas to those in adjacent bare ground regions. To account for possible cold air advection from the snow area, weather stations located along the edge of each stripe are placed into a separate category.