The purpose of this work to study, analyze and evaluate the patterns of spatial variability of long-term fluctuations in winter extreme low temperatures of the surface layer of atmospheric air in mountainous territories of Armenia (for example, the lake Sevan basin). To achieve this goal, the results of actual observations by Armhydromet and the available literary sources have been collected, processed and analyzed. As a result of the analysis of the values of extreme low temperatures, it can be noted that the genesis of winter extreme low temperatures is different in the territories under consideration. Winter extreme low temperatures stand out for their uneven distribution – they range from -26.3 to -38.1. For the calculation of winter extreme low air temperatures of unexplored or poorly studied territories, correlations were obtained between the value of extreme low temperatures and the altitude of the area above sea level. In the study area, a tendency towards an increase in winter extreme low temperatures is mainly observed. The scientific novelty of the obtained results lies in the fact that in modern observational materials, for the first time, the regularities of the variability of the spatio-temporal distribution of winter extreme low temperatures of the surface air layer in the lake Sevan basin are estimated. Findings • The study of the patterns of variability of the spatial-temporal distribution of winter extreme low temperatures of the surface air layer under conditions of regional and global climate change is an urgent task of modern geographical science; • Winter extreme low air temperatures are mainly due to the nature of the underlying surface and the features of the relief. The smallest values are observed not in high-altitude zones, but in those places where cold air accumulates (that is, in depressions). In winter, in the hollow valleys, an inversion is mainly observed- in parallel with the height, the air temperature rises. In valleys, as a result of the accumulation of cold air, low temperature conditions can be observed for quite a long time; • The study area is distinguished by a characteristic regime and an uneven spatial distribution of winter extreme low temperatures. They range from -26.3 (Semenovka) to -38.1(Masrik). • Winter extreme low temperatures rise up to 2000-2100m with altitude, and on the contrary, they decrease at altitudes above 2000-2100m. The vertical temperature gradient is -0.5C/100m and 0.8C/100m, respectively; • On the basis of the obtained correlation between winter extreme low temperatures and terrain heights, two regions were identified: 1) heights up to 2000-2100m and 2) 2000- 2100m and higher; • Temporal trends during perennial winter extreme low temperatures are mixed. In the study area, these is a predominance of positive trends. Negative trends are characteristic for the period 1935-1966 at the Sevan, Masrik and Martuni meteorological stations; • In the study area, winter conditions become thermally milder, which should be taken into account when developing strategic programs for the future development of this area.
Investigation on the Changes in the Temperature that is Caused in Vortex Tube