CLIMATIC RELATIONSHIPS BETWEEN AIR TEMPERATURE AND WATER TEMPERATURES IN DIFFERENT LIMNIC AREAS OF LAKE LADOGA
M.A. Naumenko, V.V. Guzivaty
Institute of Limnology Russian Academy of Sciences, St. Petersburg Federal Research Center of the Russian Academy of Sciences, St. Petersburg, Russia
Keywords: temperature hysteresis, dimictic lake, integral temperature of the water column, seasonal course of parameters of the near-water layer, climatic norm, heating and cooling periods of the lake
Abstract
Based on an extensive database, it is shown that for different limnetic regions of Lake Ladoga there occurs a temperature hysteresis phenomenon for the period of open water from May to November. The heating and cooling features of both the water surface and the integral water temperature of six different areas of the lake have been revealed, depending on air temperature of near surface layer. The approximation of dependencies between these parameters, the second- and third-degree polynomials, has shown that there are stable, meaningful relationships (p < 0.05) between them, with the determination coefficient of 0.8-0.9. Analytical dependencies allowed to calculate the increase in water temperature when the air temperature changes by one degree. On Lake Ladoga, a dependence of the rate of change in water surface temperature on air temperature is found. The biggest changes occur during the heating period. In August, at maximum air temperatures, the rate of increase in water surface temperature, especially in the deep-sea region, exceeds the rate of increase in air temperature. Canadian limnologists obtained similar results on Lake Ontario. Two important periods have been identified when the lake cools: the first one, when the surface temperature has a constant value with minimal spatial variance; and the second one, when the entire water thickness of the lake has the same water temperature with minimal spatial variance. These periods and values of water and air temperatures can serve as climatic norms in climate studies. Climatic changes in air temperature will affect the increase in water temperature in different ways in different seasons and in different areas of a large lake.
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