Vertical and Horizontal Distribution of Water Temperature During the Spring Thermal Bar in Lake Dolgoye (Belarus) Based on Measurements and Mathematical Modeling Data

Abstract

The purpose is to analyze the vertical and horizontal distribution of water temperature in the Dolgoye Lake during the development of the spring thermal bar in 2024. Materials and methods. At the end of March 2024, during fi eld research at the BSU Research Laboratory of Lake Studies, the spatial distribution patterns of water temperature in the Dolgoye Lake were established. The results of fi eld studies were compared with the results of mathematical modeling. Results and discussion. As a result, it was established that the thermal bar in the Dolgoye Lake existed from March 26 to 31, 2024. During this period, the water temperature near the shores varied from 4 to 8 °C, in the open part of the lake − from 0.8 to 4 °C. Modeling of physical processes showed adequate reproduction of water temperatures on March 30-31, 2024 in the bottom layers of the lake, in the near-surface they were overestimated relative to the observed ones by 0.5-1.4 ℃, which is due to the lack of observation data on March 24-29 and underestimation of the role of wind mixing in the formation of the thermal structure of the Lake Dolgoye. To the south of the reach with maximum depth, the calculated temperatures are lower due to the movement of the thermal bar front from all shallow waters, and not only from the side of the stream from the Svyadovo Lake. Conclusion. Due to the shallowness of the Dolgoye Lake compared to the Lakes of Baikal, Ladoga, and others, as well as the orientation of the lake's long axis in the direction of prevailing winds, the direct temperature stratifi cation before the destruction of the thermal bar in the Dolgoye Lake did not have time to form due to very rapid warming against the background of active wind mixing. Surface water temperatures are found to be overestimated, while in the bottom layers they are almost equal to those measured.