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Two approaches have been attempted to establish an icing climatology over Europe. Firstly, a climatology has been established by using the results of SIGMA (Severe Icing Geographic identification in Meteorology for Aviation). The situations calculated by SIGMA during two winters have been studied. Secondly, a climatology of the occurrence of freezing precipitations at ground level has been established. It is based on reports of freezing precipitation in SYNOP messages from the winters covering the years 1995 to 1998. The geographical domain covered is Western and Central Europe. The frequency of occurrence of freezing precipitations (freezing rain, freezing drizzle and ice pellets) and freezing fog was computed. The results of these two climatologies show that north eastern Europe is more prone to icing phenomena.

Icing is a very dangerous phenomenon in aeronautics. In order to help the forecasters to predict icing conditions, Meteo-France has developed a system for the identification of icing areas, named SIGMA (System of Icing Geographic identification in Meteorology for Aviation). This system is based on the combination of three different sources of data: an icing risk index calculated from Météo-France's numerical weather prediction model, the infra-red data from the geostationary Meteosat spacecraft, and Météo-France's operational centimetric radar network. This system has been verified in two manners. Firstly, an icing PIREP collection campaign was organized with French Air Force during one winter. The output of SIGMA together with the SIGMET messages were compared with the PIREPs. SIGMA showed encouraging detection rates. Then, last winter, a comparison by the forecasters between radiosoundings and the results of SIGMA has confirmed these good results.