A climatological study of surface freezing precipitation in Europe

Abstract

A climatological study of the occurrence of freezing precipitation at ground level is presented. It is based on reports of freezing precipitation in SYNOP messages from the three winters covering the years 1995-1998. The geographical domain covered is Western and Central Europe, extending northwards to Scandinavia and southwards to North Africa. The types of freezing precipitation selected are freezing rain, freezing drizzle and ice pellets. The frequency of occurrence of each of these types of freezing precipitation was computed. The results show that freezing precipitation is not an uncommon phenomenon in Europe, with the combined frequency of the various types of freezing precipitation (either drizzle, rain or ice pellets) being 0.5 to 1% of all SYNOP messages that include an observation of the current weather in Central Europe. The surface air temperature intervals associated with freezing precipitation have been studied. An attempt was then made to determine the mode of formation of freezing precipitation (either by melting of snow crystals in a layer of positive temperatures or by a process of coalescence or diffusional growth) by studying the thermodynamic soundings associated with freezing precipitation events.