CONDITIONS FOR FREEZING PRECIPITATION AT AIRPORTS OF RUSSIA AND CIS. Ⅲ. THE AIRPORT OF ODESSA

摘要

Data of hourly surface observations for 1986-2001 at the airport of Odessa and in the neighboring port of Il'ichevsk, radiosonde data, and objective analysis data are used to study conditions associated with the occurrence of freezing rain and freezing drizzle. Cloud tops were estimated from the radiosonde data. It is shown that the frequency of occurrence of freezing rain (in comparison with freezing drizzle) in Odessa is rather high, more than 56% of all the cases of freezing precipitation, which is twice as high as that in Moscow. The layers of positive temperature inside the cloud are also observed relatively often (26% of ra-diosoundings in freezing precipitation). All the cases of freezing rain (not drizzle) are associated with warm layers in or below the cloud. In Odessa, freezing precipitation at negative temperatures in the whole layer is less frequent than at other locations (26% of the cases). Objective estimation of synoptic conditions for freezing precipitation reveals its increased frequency in the areas with large gradients of surface temperature, with high baroclinicity in the lower troposphere, and especially in the areas of warm advection. It is concluded that the Mediterranean cyclones contribute largely to the occurrence of freezing precipitation in Odessa.