海上雷雨大风形成机制的分析

Study of the Forming Mechanism of Thunder Wind on Sea

用舟山群岛自动测风站资料分析了一次雷雨大风过程 ,这次雷雨大风以偏东风为主 ,自东向西传播 .并用MICAPS系统下发的T2 13资料进行诊断分析 ,分析表明这次对流系统的发生是从低层开始的 ,85 0hPa的暖平流以及夜间海洋暖水面提供了热源 ,使低层气压降低 ,高层气压升高 ,低层产生局地气旋性环流 ,高层维持反气旋性环流 ,产生斜压不稳定 ,积聚能量 .暖下垫面范围进一步扩大 ,太阳的辐射加热以及舟山群岛地形的抬升作用是触发机制 .高空急流通过雷暴系统内部的垂直环流下传动量是雷雨大风产生的直接原因 .最后总结出几个雷雨大风预报的着眼点 .

The statistics of the automatic wind observatories in the Zhoushan Archipelagos and the data provided by T213 in the MICAPS system about a process of thunder wind are studied. It is shown that this convective process is originated from low layer air. The warm advection in 850 hPa and the warm sea in night provide the warm source, which make the law air pressure descend and the upper air pressure ascend. Then a clockwise circle is produced in low air and the counterclockwise circle in upper air maintains. At the same time, baroclinic unstability is forming and energy is being collected. The trigger mechanism is the enlargement of the range of the warm surface, the radiation of the sun and the orographic lifting in the Zhoushan Archipelagos. The direct reason to produce the thunder wind is that the upper jetstream disseminate momentum down through the vertical circle in the thunder system. At last some focuses of attention to forecast thunder wind are provided.