ANALYSIS OF THE VARIABILITY OF THE WINTER PRECIPITATIONS AND TEMPERATURES IN TWO MOUNTAIN REGIONS OF BULGARIA

Snow cover is an indicator of the fluctuating climate, resulting from the change in the regime of winter precipitations and air temperatures. Our previous study has revealed significant decreasing of the snow cover in the high altitudes of Vitosha mountain. The current sturdy is now focused on these two meteorological variable � the type and amount of the winter precipitations and the seasonal change of the air temperature. Monthly and seasonal values of precipitation amounts, number of days with different type of precipitation and mean air temperature from 6 meteorological stations in Vitosha and Stara planina have been used in this survey. The main period of investigation is 1960-2021 and the stations altitudes range from 1000 up to 2376 m. Statistical analysis is performed in order to assess the variability and possible differences in the investigated characteristics from long-term data series for two main climatological periods 1961-90 and 1991-2020. Statistically significant decreasing tendencies in the precipitation amounts have been discovered for all stations. Increasing trend of the mean seasonal air temperature is also observed, however manifestly only for the highest regions where remarkable rising tendency could be determined in the beginning of the 1990-es. Number of days with snowfalls also shows declining behavior in agreement with the general precipitation amount tendency. Recently increasing days with rain could be find out only in the high altitude regions of Stara planina. This investigation is part of a common project for investigation of the current variability of the snow cover and winter precipitations in the mountain regions of Austria and Bulgaria and is funded by the Bulgarian National Science Fund and the Austria's Agency for Education and Internationalisation in the call of the bilateral program Scientific and Technological Cooperation between both countries.