DYNAMIC INFLUENCE OF QINGHAI-XIZANG PLATEAU AND ROCKY MOUNTAINS ON THE LEE CYCLONES

Using the operational model(B model) of Beijing Meteorological Center,we do some of numerical experiments of crossing and rounding mountains in all velocity adjustment scheme,and study dynamic effect of Qinghai-Xizang Plateau and Rocky Mountains on lee cyclones.The results show that due to air flow round the Qinghai-Xizang Plateau,divergence is distributed in the shape of confluence which matches cyclogenesis area and cyclonic track in East Asia.In the downstream of the Qinghai-Xizang Plateau,convergence in the upper troposphere restrains cyclone development in the east of China mainland.In North America,air flow primarily crosses over Rocky Mountains.Air is adiabatically cooled when it flows upward in the west flank of Rocky Mountains,while air is warmed when it flows downward in the lee side.The fact is important for the lee cyclogenesis and the lee frontogenesis of Rocky Mountains.Air flow crossing over Rocky Mountains is also the main cause for forming dryline in the mid-west of United States.