山地背风涡旋的数值研究

本文建立了一个三维原始方程数值模式，模拟山地背风坡的环流系统。模拟结果表明，在较强层结条件下，山地背风坡上地形性中尺度斜压性大大加强，引起背风坡上的反向环流和涡旋偶极子，非粘性动力强迫效应是流场分离的重要机制。

NUMERICAL EXPERIMENTS OF MOUNTAIN LEE VORTICES

Many observations have confirmed that under strong atmospheric conditions, leecyclone wavesare often formed at the leesides of mountains and islands.For a long time this kind of lee cyclone isconsidered to be caused by planetary boundary layer frictional effects.Further analysis shows thatthe formation of mountaion lee cyclone has much more complicated mechanism.Traditional mountainclimate theory is limited in low-amplitued perturbation theory,it is invalid in non-linear areas.Forthis reason we set up a three-dimensional numerical model to simulate mountain-induced lee vorticesand discuss the role of surface friction,stratification and coriolis force in this kind of circulation.Model results show that under strong stratification there is reversed flow in the lee of mountain.The reversed flow Is strongest In the center line,and a depole of lee vortices if formed symmetricallyalong the center line.surface friction weakens the strength of reversed flow,but enlarged the extention of lee vortices.Non-frictional dynamic effect is the basic reason for the flow separation.In thecondition of weak stratification large-amplitude mountain waves develop and an area of low velocityappears in the leeside of mountain.No reversed flow and lee vortices form under this condition.Under strong stratification we consider both coriolis force and surface frictional effects,and model simulations show that in the leeside of mountain,the depole of lee vortices disappears,while cyclonewave develops;this kind of circulations is very similar to those observed in real atmosphere;