ИСТИНА

Ablation of mountain glaciers is determined by the heat balance of the surface, the main components of balance are: radiation balance, turbulent heat exchange between glacier surface and the atmosphere, the loss of heat by evaporation, heat flux into the ice body, heat from the liquid precipitation, as well as the heat of condensation on the surface. Depending on the region and season, the role of each component of the heat balance varies. Quantitative assessment of these components is needed to understand the physical mechanisms of ablation, which is a critical component of the mass balance of the glacier. This requires a whole set of meteorological observations. A systematic meteorological and actinometrical observations and the level of the ice surface monitoring are conducted on glacier Dzhankuat since 2007 in the ablation period (June-September) with an automatic weather station CAMPBELL. Since 2010, there were a few sets of gradient observations with Assman psychrometers and Fuss anemometers. In 2014 a direct measurements of turbulent heat flux were made using acoustic anemometer GILL. As a result, values of the radiation balance and turbulent fluxes were obtained in the last 7 ablation seasons with the help of different methods (heat balance method, Monin-Obukhov method, method of turbulent pulsations). It was shown that, depending on the cloudiness determined by the synoptical conditions, the contribution of the radiation balance in the total energy ablation varies between 80-90%, the sensible heat flux is 7-15%, and the loss of heat by evaporation from the surface of the glacier is 2- 4%. It was shown also that such variables as heat flux into the ice, heat flux with liquid precipitations and heat of the condensation on the surface are negligible and do not exceed 1%. Thus, the main factor determining the ablation of glaciers of the Central Caucasus is radiation balance.