西风带南支槽对云南天气的影响

利用中国2 474个台站观测逐日降水资料和美国NCEP/NCAR再分析资料，分析了2015年冬季云南两次强降水的极端特征及其环流异常演变特征，讨论了降水异常与大气低频振荡的关系。
结果表明：两次过程强降水期间南支槽、水汽和偏南急流均具有异常特征，且第一次过程的异常强度明显强于第二次过程；中高纬源自北大西洋的Rossby波能量频散对云南极端降水有明显作用，南支槽前的西南急流和菲律宾副热带系统的西北传播和云南极端降水也关系密切；第一次过程的波作用能量的传播方向、辐合程度以及菲律宾-南海-中南半岛-云南的显著垂直环流圈均较第二次过程更加有利于云南低频降水的增强，进而导致了两次过程降水强度和范围的差异。

The NCEP/NCAR 40 Year Reanalysis Project

Based on the daily precipitation data from 2 474 stations in China and the National Centers for Environmental Prediction-Department of Energy (NCEP-DOE) daily reanalysis data, the extreme characteristics of two heavy precipitation events in Yunnan in winter of 2015 and the evolution characteristics of circulation anomalies are analyzed, and the relationship between precipitation anomalies and atmospheric low-frequency oscillations is discussed. The results suggest that the South Branch trough, water vapor and the South jet have anomalous characteristics during the two heavy rainfall events. The abnormal intensity of the first event is obviously stronger than that of the second event.
The energy dispersion of Rossby waves originating from the North Atlantic in the middle and high latitudes plays an important role in the extreme precipitation in Yunnan province. In addition, the southwest jet in front of the South Branch Trough and the northwest propagation of the Philippine subtropical system are closely related to the extreme precipitation in Yunnan province. The wave action energy propagation direction, the convergence degree and the significant vertical circulation circle of Philippines-south China sea-Indochina peninsula-Yunnan in the first event are more conducive to the enhancement of low-frequency precipitation in Yunnan than those in the second event, which leads to the fact that the range and intensity of the first precipitation event are stronger than that of the second precipitation event.