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The variations in several climatological characteristics are studied on the basis of hourly (half-hourly) meteorological terminal observations at 51 aerodromes of the Russian Federation in 2001-2015. For every aerodrome extreme temperature, wind speed and gusts, and QNH are analyzed for the above period. Using data for three consecutive 5-year periods, variations in the number of days with temperature above 30°C or below -30°C, with wind speed of ≥10 m/s and gusts of ≥15 m/s are considered. The occurrence frequency of significant weather events affecting the takeoff and landing (fog, blizzard, freezing precipitation, thunderstorm) is investigated. The results for aerodromes with positive or negative trends in the occurrence frequency of weather phenomena in 2001-2015 are presented. [ABSTRACT FROM AUTHOR]

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Conditions for freezing precipitation (FP), including freezing rain (FR) and freezing drizzle (FZ) for 8 airports in Russia and 4 in the Ukraine are studied on the basis of 10 to 20-year series of surface observations, radiosonde and objective analysis data. Statistical characteristics are presented of the FP episode durations and of occurrence frequency dependences on surface air temperature, wind direction and speed and cloud base height. From the radiosonde data, it is found that the "classical mechanism" of FP generation (for which, stratification of "warm nose" type in the cloud layer is necessary) is not frequent: most of FP cases are associated with "all cold" conditions in the lower 3-km layer, that is, with negative temperatures in and below the clouds. [ABSTRACT FROM AUTHOR]