南方地区连续暴雨过程扰动能量的积累和传播分析

ANALYSIS OF THE ACCUMULATION AND PROPAGATION OF WAVE PACKETS DURING A HEAVY RAINFALL PROCESS IN SOUTHERN CHINA

利用NCEP/NCAR再分析资料,通过波包传播的诊断方法,对2008年5月26日—6月18日我国南方地区连续暴雨过程期间波包传播和积累进行分析与研究。由中低层500 hPa和700 hPa高度场的波包分布特征分析可知,强降水过程产生期间,绝大部分发生强降水的地区均是波包大值区,扰动能量的积累和释放与降水过程的发展有一定对应关系。扰动能量的发展和积累与强辐合区内不稳定能量的输送也有较好的对应。波包值的经向和纬向传播特征表明,在强盛的西南季风背景下,这次南方地区连续暴雨过程的扰动能量主要来自孟加拉湾地区,在降水期间有源源不断的波包由该地区向降水区域传播;西太平洋副热带高压(简称西太副高)所处的高值区范围偏南,有利于副高北侧西南气流扰动能量的传播;高原地区的扰动能量对降水也有重要影响,南支锋区扰动异常活跃。中低层扰动能量的传播、积累及频散与降水的发生、维持及结束有着紧密的联系。

Based on the NCEP/NCAR reanalysis data and a diagnostic analysis of wave packet propagation （WPD）, the propagation and accumulation of wave packets during a sustained southern China heavy rainfall process are analyzed. The characteristics of wave-packet propagation at 500 hPa and 700 hPa indicate that most of the area where heavy precipitation took place was in the area controlled by large wave-packet values. Development and accumulation of perturbation energy correspond better to the transport of unstable energy in the strong convergence area. In the background of a powerful southwest monsoon, the perturbation energy of this strong precipitation is mainly from the Bay of Bengal area; wave-packets kept spreading to the area during precipitation; as the western Pacific subtropical high is located more southward than usual, it is favorable to the propagation of perturbation energy by a southwest air current north of it; the perturbation energy of the Tibetan Plateau also influenced the precipitation. The propagation, accumulation and break-up of the perturbation energy have close relationships with the emergence, sustaining and ending of the precipitation.