长江中游区域性暴雨发展机理合成分析

Composite Analysis on the DevelopmentMechanism of Regional Torrential Rainover the Mid Reaches of the Yangtze River

利用高分辨 TBB资料、逐 6h NCEP/NCAR再分析资料和逐日降水资料及SCSMEX降水加密观测资料,通过对长江中游 8次区域性暴雨的合成分析,研究发现:暴雨落区发生在急流出口区南侧与南亚高压脊线近极地一侧之间发散气流辐散加强的区域附近;且与东亚副热带地区季风涌相关联;高空非地转惯性平流风散度是高空总散度的主要贡献者,高空倾斜急流轴(NW－SE向)出口区水平风场的分布不均匀,导致其出口区的右侧产生较强的辐散场,由于对流风的作用,低层辐合会对高层辐散产生响应,从而诱发暴雨发生。高空急流轴倾斜以及急流出口区右侧强辐散场的出现要早于暴雨的发生。

In the context of high-resolution TBB data, every 6h NCEP/NCAR reanalysis data sets and daily rain data, the mechanisms for the regional torrential rain development over the mid-Yangtze River basins are investigated by means of composite analysis. The results show that the heavy rainfall event often occurs in the area where the upper level diverging flow appears, and heavy rainfall is also related to East Asian Subtropical monsoon surge. Result further indicates that the ageostrophic inertial advection divergence makes the major contribution to the total upper level divergence fields. Due to the role of NW-SE oriented upper tropospheric jet axis, the distribution of horizontal wind field will be inhomogeneous on the jet exit area, and results in strong convergence over the right side of the upper level jet. The incline jet axis and strengthened convergence happen earlier than the rainfall does.