本文用合成方法计算了夏季两类500hPa移出低涡的基本物理量场和涡度平衡。计算表明:西风带下高原低涡在高原西部有爆发性冷槽时才能移出,其移向移速受300-200hPa气流引导;东风带下低涡受印度西南季风向我国东部爆发所引起的强降水中心操纵。

Using the composite analysis method, We analysed both basic meteorological element fields and the vorticity balance of two types of 500hPa plateau vortexes which moved eastward out of the plateau on 500hPa in summer. It is shown that the westerlies vortexes can be moved eastward out of the plateau only when there is a explosive cold trough in the west part of the plateau.Their moving directions and velocities are steered by the flow between 200 and 300hPa;The easterlies vortexes moved under control of the centre of heavy precipitation which was resulted from Indian monsoon stretched eastward East China.