Regional and local influences on freezing drizzle, freezing rain, and ice pellet events

Regional and local influences on frequency and type of freezing precipitati on (freezing drizzle, freezing rain, and ice pellets) are investigated via in-depth climatologies of six continental United Stares (CONUS) sounding si tes. For each site, wind roses of precipitation type occurrences are compar ed with those for nearby stations and the aggregate values for the CONUS. S ynoptic scenarios and sounding structures are identified for prolonged even ts of each precipitation type and probable formation mechanisms are discuss ed. Station location relative to topographic features smaller than 1 km in height, water bodies ranging in size from oceans to small bays, and dominan t wintertime storm tracks are shown to play a major role in the determinati on of the frequency and type of freezing precipitation at each site. Result s help to explain the regional maxima and minima of freezing precipitation across the CONUS, as well as the dominance of certain precipitation types a nd formation mechanisms in different portions thereof. Understanding these differences is necessary for proper development of techniques used to diagn ose and forecast surface precipitation type and the occurrence of hazardous aircraft icing conditions associated with Freezing precipitation aloft.