中国东部夏季极端降水年代际变化特征及成因分析

本研究利用逐日降水资料对中国东部夏季极端降水进行检测，并对转变前后的特征进行对比分析，进而从海、陆对增温的响应不同导致的环流调整给出成因分析。结果表明，（1）中国东部夏季极端降水在1990年前后出现显著的年代际转变，极端降水由偏少转为偏多。转折后与转折前相比，中国东部夏季极端降水落区南移，南方偶极子分布型加强，南方极端降水增加、北方极端降水减少，其中华南和华东地区，极端降水量和降水日数增加，对夏季降水的贡献率增大；华北地区，极端降水量和降水日数减少，对夏季降水的贡献率减小。（2）西太平洋暖池区异常升温造成的海陆温差减小是中国东部夏季极端降水1990年前后转变的重要驱动因素之一。它造成1990年之后低纬度季风强度减弱、西太平洋副热带高压增强并南移、南海副高增强，而中高纬度气旋性环流异常被破坏、东亚大槽增强，进而导致华北经向水汽输送减弱，下沉运动显著加强，极端降水量和降水日数减少。于此同时，华南和华东地区则水汽输送加强，上升运动显著，有利于降水偏多，并伴随极端降水量和降水日数有所增加。

Analysis of the Characteristics and Causes of Interdecadal Changes in the Summer Extreme Precipitation over Eastern China

Using daily precipitation data from eastern China, in this study, we investigated the interdecadal shift in the summer extreme precipitation (SEP) and analyzed the characteristics before and after the climate shift. We also analyzed the cause from the perspective of different responses to global warming between land and ocean, which leads to circulation adjustments. The results show that the SEP in eastern China exhibited an obvious interdecadal shift around 1990, after which it became a positive anomaly. Compared with the SEP before the shift, the distributions of major modes shifted south, the intensity of SEP was enhanced, and the contribution rate to summer precipitation increased in both South and East China, whereas in North China all of these factors exhibited the opposite change. The change in the temperature difference between land and ocean caused by the strong positive anomaly of the sea surface temperature in the western Pacific warm pool is one of the important factors driving this shift, leading to the interdecadal adjustment of the East Asia summer monsoon system. In the low–middle latitudes, the intensity of the summer monsoon weakened, the West Pacific subtropical high strengthened and moved south, and the South China Sea high was also enhanced. In the middle–high latitudes, this cyclonic anomaly was broken and the East Asia Trough strengthened. Under the influence of this circulation adjustment, the water vapor decreased (increases) and vertical motion weakened (is enhanced) in North China (South and East China). Thus, the SEP decreased in North China and increased in South and East China.