贵州初夏两次暖区暴雨的对比分析

利用常规气象观测资料、NCEP 1°×1°格点再分析资料和FY 2D卫星红外云图云顶亮温TBB资料，对贵州2008年5月25—26日(简称08.05)和2010年6月28—29日(简称10.06)初夏两次暖区暴雨天气过程进行对比分析，探讨两次暴雨发生发展的天气学条件差异。结果表明：暖区暴雨形成时，地面均为热低压控制，地面辐合线加强触发暖区暴雨发生；850 hPa低空急流明显加强，暴雨区位于低空急流左前侧。所不同的是：两次暴雨过程中高层影响天气系统不同，08.05暴雨中层影响系统为高原槽，10.06暴雨中层影响系统为两高切变低涡，高层为南亚高压脊。08.05暴雨过程中，多个β中尺度对流单体独立发展逐渐合并为一个α中尺度对流系统，对流云发展旺盛、伸展高度较高、具有混合相层和暖云层剖面结构，属于积状云为主的混合降水。10.06暴雨，经历了两次β中尺度对流系统的发展和减弱，对流云团呈东北—西南向的带状和椭圆状，对流发展高度较低，具有深厚的暖云层，回波在暴雨区持续时间较长，属于层状云和积状云混合降水。通过对两次暴雨触发机制讨论得出，贵州暖区暴雨预报应着眼于影响贵州的低空急流的建立和加强以及地面低压中辐合线的加强锋生。

Comparison Analysis of Two Warm Area Torrential Rain Systems in Early Summer in Guizhou

In eastern China, there is one kind of rainfall that is related to the upper troposphere anticyclone, i.e., the South Asian High (SAH). The average heavy rainfall of central eastern China in annual cycle happens in the northeastern side of the SAH ridge line and shows a quasi biweekly oscillation in latitude when the SAH ridge line shifts northward or southward. The satellite water vapor (WV) images reveal the atmosphere movement of upper troposphere. The WV image and the derived wind can describe the location of the anticyclone center of upper troposphere and its ridge line and can also trace the downward dry and cold flow from middle high latitude, which is important to heavy rainfall in summer. The small scale dark area extending southward on WV images is usually the strong potential vorticity area in mid high latitude, and it can intensify the rainfall when moving to rainfall belt. There are two severe rainfall areas related to the SAH, one is in the southwest side of the SAH and another is in the northeast side of the SAH where the flow is divergent in the upper troposphere. In the north side of the SAH subtropical westerlies exist when the westerlies are strong, the divergence in the northeast side of the SAH in the upper levels is strong, which can induce strong precipitation in China. The SAH can affect most of China when it advances and withdraws from early May to early October. As a result, the concept model of the satellite image characteristics which is got from the cases over Huaihe River region in summer can also be used in other seasons or places such as Northwest China and North China regions. The location and shape of the SAH can affect the region and intensity of heavy rainfalls and meanwhile severe precipitation also has feedback on the SAH, leading the asymmetric instability development of the SAH.