华南连续性特大致洪暴雨个例分析

Case Study of Extraordinary Flood-Inducing Rainstorm in South China

利用气象常规观测资料及NCEP／NCAR再分析资料，从越赤道气流、降水时空分布以及过程开始、持续和结束环流时特征等方面对2005年6月18-24日华南连续性特大致洪暴雨过程进行了分析。结果发现，暴雨的空间分布有着双雨带特征，即南北两条雨带，北面雨带对应着切变线，南面的雨带对应着低空急流；暴雨开始前及暴雨过程中，索马里附近一直维持强盛的越赤道气流，同时在100°～160°E之间也有越赤道气流活动并有西进现象；500hPa西风槽、850hPa切变线是这次过程开始和维持的重要系统；华南上空对流层高层东风的建立是这次过程结束时重要特征；南海北部至广东上空低空急流中心风速的周期性脉动与广东强降水的日变化现象有着很好的对应关系。

The extraordinary flood-inducing rainfall in South China in June 2005 is analyzed synoptically on the basis of the conventional observation data and NCEP/NCAR reanalysis data. The results show that the heavy rainfall, which had two main rain belts and significant daily variations, was mainly associated with the active 500 hPa trough, 850 hPa shear line, low-level jet and cross-equatorial flows. The westerly fluctuations related to the 500 hPa trough and 850 hPa shear line （tropical systems related to the strong southwesterly and cross-equatorial flows） mostly account for the rain belt in the northern （southern） part of Guangdong province. As the activities of the westerly fluctuations decayed, the north rain belt decreased gradually. The southern rain belt had the peak periods of rainfall corresponding to the peak phrases of the meridional winds in the mid-low layer over the southern coastal area, which indicates the impacts of the low-level jet. The occurring of heavy rainfall was induced by the strong cross-equatorial flows, which provide sufficient water vapor for South China, and the end of heavy rainfall is featured by the buildup of the upper-level easterly.