摘要
本文对北半球大湖中普遍存在的大规模反时针环流的形成,提出了一种物理解释,认为大气在经过湖体时的地转适应过程产生了一个有利于这种环流形成的附加风场。这种环流的强度在一年四季中是变化的,夏季最强,冬季最弱。在此理论的基础上建立了一个三维非线性水动力学数学模型。数值试验表明,风场的有旋性对这种环流的形成起了决定性的作用。计算得到的环流形态基本上与实测结果相吻合。
It is well known that in large lakes in the northern hemisphere there exist large scale cyclonic circulations. Their formation and maintenance mechanisms have been studied by many researchers. Emery and Casanady (1973)'s explanation is that as warm surface water advects to the right of the prevailing wind the increased wind drag over this warm water results in a cyclonic wind stress that drives a cyclonic circulation. It can explain this phenomenon very well rather in summer, than in winter. In this paper, another mechanism is proposed to complete the Emery and Csanady's explanation.Analyses show that when wind goes over a lake, it always creates addtional cyclonic wind field which drives a cyclonic circulation, besides, if the lake shore is unsymmetrical about the center, the unsymmetry may affect the circulation, comparison of Emery and Casanady's mechanism with ours, we can see that they caused the same sign rotation in summer and different sign rotation in winter, so we come to a conclusion that the circulation is changeable with seasons, strongest in summer, weakest in winter, which is confirmed by the observation data from the Biwa Lake Research Institute of Japan.Based on this theory, we designed a three-dimensional, non-linear hydrodynamical model. test showed that the rotation of wind is essential to the circulation of lakes. The calculation results generally coincide with the observation ones.In this model, we neglected (did not count) the income and output water of the lake, thus making the calculation results differ more or less from the observation values. Because of lack of observation data in winter, we can not discuss the circulation pattern and evolution law in winter, which will be investigated in the future.
出处
《海洋与湖沼》
CAS
CSCD
北大核心
1991年第4期329-337,共9页
Oceanologia Et Limnologia Sinica
