琵琶湖是日本第一大湖，面积约６７３．８ｋｍ￣２，最大水深１０４ｍ，湖泊四面环山，地形复杂。本文首先建立了流域复杂地形下的三维非定常大气边界层数值模式和湖泊三维正压水动力学数值模式。湖泊水动力学数值模拟工作在国内虽然取得了很大进展，但大多数只适应于浅水湖泊，停留在三维正压水动力数值模式基础上，对深水湖泊的三维斜压模型的研究仍然是一空白，另外，目前世界上湖泊水动力数值式发展很快，但使用的湖面风场、温度场等条件均是假设的，十分不合理。所以，本文接着着手建立了三维斜压水动力数值模式和三维大气－斜压水动力耦合模式。当前，由于世界各大湖泊均面临富营养化等水质恶化问题，而要探索水质的改善途径，首先必须弄清水中各污染物传输、扩散的规律，因此研究湖泊环流机制变得尤为重要。对琵琶湖环流形成机制的讨论已有很多年了，这一直是物理湖泊学家们观测研究的重要课题，本文运用数值模拟的方法对此作了深入探讨，并取得了一些有益的结果，证明了濮培民（１９８７）的理论分析结果，认为在北半球大湖中普遍存在的气旋式环流主要是水陆动力特性差异形成的，热力因素起辅助作用。重要结论如下：１）在弱的背景风场下，夜间边界层风场在低层向湖区辐合，并向地势较低的湖南 Lake Biwa is Japan’s largest lake, an area of ​​about 673.8km ~ 2, the maximum depth of 104m, the lake surrounded by mountains, the terrain complex. In this paper, three-dimensional numerical model of unsteady atmospheric boundary layer and three-dimensional hydrodynamic numerical model of lacustrine lake under complex terrain are established. Although the great progress has been made in the numerical simulation of lake hydrodynamics in China, most of them are only adapted to shallow lakes. Based on the three-dimensional numerical model of positive hydrodynamic pressure, the study on the three-dimensional baroclinic model of deep lakes is still a In addition, at present, the hydrodynamics of lakes in the world has developed rapidly. However, the conditions of lake surface wind field, temperature field and so on are hypothetical and unreasonable. Therefore, the paper proceeds to establish three-dimensional baroclinic hydrodynamic numerical model and three-dimensional atmospheric-baroclinic hydrodynamic coupling mode. At present, all major lakes in the world are experiencing the problem of water quality deterioration, such as eutrophication. To explore ways to improve water quality, we must first understand the law of transmission and diffusion of pollutants in water. Therefore, it is particularly important to study the circulation mechanism of lakes. For many years, the discussion on the formation mechanism of the Biwa Lake circulation has been an important topic observed and studied by the physical lake scientists. In this paper, the numerical simulation is used to discuss this and some beneficial results are obtained. Pu Peimin (1987) theoretical analysis, that the prevalence of cyclone-type circulation in the Great Northern Hemisphere is mainly formed by the difference of hydrodynamic characteristics, the thermal factors play a supporting role. The main conclusions are as follows: 1) In the weak background wind field, the wind field at the night boundary layer converges to the lower reaches of the lake and lowers toward the lower reaches of Hunan