Air-Sea/Lake Interaction of a Shallow lake and Coastal Zone with application
Presenting person: Prof. Dr. Gennady N. Panin, Institute of Water Problems, Moscow, RussiaTh. 2005-06-09 (16:15), H6
This report consists of 2 parts. The first one gives a description of a model for the air-sea/lake interaction. The second part presents an application of the model for the lake heat balance analysis and its hydrobiological condition.
It is shown that typical air-sea interaction models can be transferred to shallow water conditions and lakes including a depth dependent function. It is assumed that exchange conditions increase as depth decreases. From our results follow that the model without the shallow water correction underestimates the latent and sensible heat fluxes of a lake by about 20 % accordingly. This was shown through the comparison of the model with eddy covariance data for a shallow lake during the LITFASS-98 and LITFASS-2003 experiments in Germany. In should be also regarded that in a coastal zone the air flux is transformed and it brings to the additional calculation difficulties for the intensity of the energy-mass exchange there. There are numerous experimental and theoretical research for this zone, including the thorough study at the internal boundary layer (IBL) structure. Though, as before, the quantitative magnitudes estimations of turbulent fluxes at this point differ a lot (up to 100%) by various authors. Based on the own experimental data of the basin depth influence on the sea/atmosphere interaction intensity there has been developed a balance model for calculation of the energy/mass exchange intensity in a coastal zone. A balance model in combination with the empirical dependence for calculation of the energy/mass exchange intensity in a coastal zone allows to calculate the momentum, heat and humidity fluxes values at different distances from a shore.
Research of the lake heat balance revealed its temperature distribution in the near-surface water layer particularities corresponding with cold, warm and isothermal type. The temperature distribution types were parameterized, what created the basis for the development of the method of the near-surface water layer temperature difference calculation, based on standard hydrometeorological information data. Eventually it was indicated that the intensity of the gas exchange through the surface may vary by few times, which could influence the hydrobiological regime of the water body. For testing of this hypothesis measurements studying of biological and chemical processes of the surface water layer considering hydrologic factors were accomplished in lakes of Russia. Measurement results showed that during day time in spring and in summer there is formed a positive gradient of temperature in the upper water layer. Oxygen saturation is lower than inside of water. Amount of bacterial cells in a surface water layer and concentration of organic substance is higher than in lower layers. Thus, the field experiment data confirmed the earlier supposed hypothesis. As a result of that there was suggested a model describing the influence of the near-surface water layer on the evolution of the water life in spring and formation of the fish killing effect in summer and autumn.
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