中国东部夏季三个雨带降水的年代际变化及其与中高纬环流和海温的关系

INTERDECADAL VARIATIONS OF MONSOON RAINBANDS OVER CHINA AND THEIR RELATIONSHIPS WITH OCEAN-ATMOSPHERIC SYSTEMS IN MED-HIGH LATITUDES

分析了华南、长江流域和华北夏季风三雨带降水的年代际变化特征及其与海气系统的关系。结果表明,三雨带的开始日、结束日都有明显的年代际变化特征,主要表现为自1990年代至今,三雨带开始日推迟,华北雨带终止日明显提前。夏季风的进程与两极涛动密切相关,也与局地海陆热力差异有关:长江流域降水对应于欧亚大陆的位势高度正异常,而华南和华北降水都对应于欧亚大陆的位势高度负异常。华南、华北降水与北太平洋中纬度SST年代际变率密切相关,而长江流域降水与北大西洋中高纬度和西太平洋暖池SST的年代际变率有关。这说明年代际时间尺度上,夏季风进程的不同阶段对应着显著的环流和海温差别,中高纬的环流和海温对夏季风降水有重要的影响。

The interdecadal variations of the three Monsoon rainbands(South China,Yangtze River Valley,North China) and their relationships with the variations in global ocean-atmospheric systems are analyzed. The results show that,there are obvious trends in the initial (final dates) identified in three rainbands, especially in NC and YRV. The initial dates are delayed and finial dates advanced since 1990's. The advance of rainbands are closely related with circulation systems in mid-high latitudes (AO,AAO) and geopotential height anomaly in the Eurasia continent. In decadal time-scales,SST in mid-high latitudes plays a very importment role in the course of monsoon rainfall. Rainfall in South China and North China is closely associated with decadal SST variability in mid-latitudes of North Pacific, while rainfall in Yangtze River Valley with that of in mid-high latitudes of North Altantic.