一次低涡东移机制的分析

Analysis of mechanism of low vortex propagated easterly.

对1999年6月25日到29日发生在长江中下游流域的低涡活动进行中尺度四维同化模拟,分析发现低涡在形成后,前期高能舌未东伸,高空辐散中心与低涡中心重合或略偏后于低涡中心,低涡不东移.当高空急流中心东跃,高低空急流开始耦合时,低涡开始东移,当低涡移到高低空急流的耦合区时,低涡东移并强烈发展.

By making fourdimensional data assimilation, the low vortex that occurred in the Middle and Lower Reaches of Changjiang River from 25 to 29 in June 1999 was studied. It was found that when the warm and moist tongue didn't stretch easterly and the highlevel divergence center was coincided with the low vortex center or a little behind it ,the vortex was steady. When the upperlevel jet center made a leap towards east and coupled with the lowlevel jet and the low vortex located in the coupling area of upperlevel jet and lowlevel jet, the vortex began to move towards east significantly and developed strongly.