中国东部夏季暴雨日数的分布特征及其与大气环流和海温的关系

采用1961—2010年NCEP/NCAR再分析资料,NOAA海表温度资料和中国国家气候中心整编的中国东部387站逐日降水资料,分析了中国夏季暴雨日数的分布特征及其与大气环流和海温的可能关系。结果表明:(1)近50年中国东部夏季暴雨日数经历了3次年代际变化,先后发生在20世纪70年代中后期、90年代初以及21世纪初。(2)根据经验正交函数(EOF)分析主模态的空间分布型,结合聚类分析的方法,将中国东部夏季暴雨日数主要分为6种类型:渤海型、北方型、淮河型、长江型、南方型、南方和北方两支型。该分型对实际暴雨日数分布具有较好的代表性。(3)分析中国东部夏季暴雨日数不同分布型的环流场特征,结果表明暴雨日数的分布类型与东亚夏季风密切相关,渤海型和北方型分布对应季风位置偏北,淮河型和长江型分布对应季风位置偏南,南方型分布时季风位置更加偏南,当暴雨日数呈现南方和北方两支型分布时,季风较强,影响中国东部大部分地区。(4)分析中国东部夏季暴雨日数不同分布型的水汽输送特征,结果表明,影响中国东部夏季不同暴雨日数分布型的水汽输送与西太平洋的异常反气旋式环流密切相关,形成暴雨的水汽更多来自于西太平洋。(5)分析中国东部夏季暴雨日数不同分布型的海温场特征,结果表明,渤海型和北方型暴雨日数多发生在拉尼娜发展或者维持时期;淮河型和长江型暴雨日数多发生在厄尔尼诺维持或者衰减时期;南方型暴雨日数多发生在厄尔尼诺发展时期;而当暴雨日数呈现出南方和北方两支型时,整个太平洋和北印度洋大部分地区均呈现出偏冷的状态,海、陆热力差异显著。

Spatiotemporal characteristics of summer rainstorm days in eastern China and their relationships with the atmospheric circulation and SST

By using the NCEP/NCAR reanalysis datasets, the NOAA SST datasets and Chinese 387-station daily precipitation data over eastern China for the period of 1961-2010, the spatiotemporal characteristics of rainstorm days during summer and their relationships with the atmospheric circulation and SST are studied. It is found that the summer rainstorm days over eastern China experience three interdecadal variation processes in the recent 50 years. According to the EOF and cluster analysis, the summer rainstorm days over eastern China are divided into six distribution patterns, namely the Bohai Sea pattern, north pattern, Huaihe River pattern, Yangtze River pattern, south pattern, and both branches pattern. The relationships between the six distribution patterns and the atmospheric circulation show that the summer rainstorm days are closely related to the East Asian summer monsoon. The Bohai Sea pattern and the north pattern correspond to the monsoon with its position by north, while the Huaihe River pattern and Yangtze River pattern correspond to the monsoon with its position by south, and the south pattern corresponds to a weak monsoon with its pisition even souther. When the both branches pattern occurs, the monsoon is strong, and affects most parts of eastern China. The relationships of the different distribution patterns with water vapor transport characteristics show that moisture transport is closely related to an anticyclonic circulation anomaly in the western Pacific with more available moisture. The relationships of the different distribution patterns with SST show that the Bohai Sea pattern and the north pattern occur more likely in the La Nia development or maintenance period, the Huaihe River pattern and Yangtze River pattern occur more likely in the El Nio maintenance or decay period, the south pattern occurs in the El Nio development period. While the both branches pattern occurs, the Pacific and most of the northern Indian Ocean show a cold state and a significant land-sea thermal difference.