Abstract: The research work of the coupling model of atmospheric boundary layer with hydrodynamics is an advanced subject in physical limnology. Yukio Oonishi etc.(1975), Casulli,V.and Cheng RT (1992), Zic K, Patterson JC etc.(1992), Zhang Limin etc.(1994) have made many numerical studies in limnology. But all the above works only concerned one of the two factors, separating lake from atmosphere.While studying hydrodynamics, they supposed that the air and temperature fields over the lake were homogeneous. but the hypothesis had much difference from reality.Because of dynamic and thermal difference between water surface and land around a lake, there form character istically inhomogenous wind. temperature, and humidity fields, and these factors have many effectson current and temperature in the lake, and thus forms a special environment. A numerical model coupling a tmosphere with hydrodynamics is set up in this paper,and it applied in the experimental study of Lake Biwa.Some results are got:(1) Whatever (SSW)in summer or(NNW)in winter,there exists a positive wind-stress curl over a lake;(2) In summer the positive wind-stress curl pays an important role to form circulation in a lake and produces a special temperature field corresponding to circulation, lower in the deep water, higher in the shallow water;(3) In summer, the hypothsis of initial horizontal inhomogeneous water temperature has little efftect on the results of simulation;(4)In winter, there is no obvious circulation formed in the lake.

Key words: Air-water couPling model, Lake Biwa, Numeric Simulation