华南6月降水的十年际和极端年际差异及其环境分析

INTERDECADAL TRANSITIONS AND EXCEPTIONAL TWO YEARS OF JUNE PRECIPITATION OVER SOUTH CHINA

6月是华南季风降水的集中季节。利用高分辨率的1978—2006年亚洲降水资料分析得到,华南6月降水存在1980—1989年的十年少降水期和1992—2001年的十年多降水期,以及2004年的极端低值年和2005年的极端高值年。以华南的十年际和极端年际降水变化为中心,存在着环南海西侧越南到华南和我国东南地区的6月降水异常的一致性分布。降水正(负)异常对应850 hPa上异常的东南(西北)风到达越南,异常的西南(东北)风到达华南沿海和我国东南沿海地区。降水十年际正(负)异常的前冬季和当年春季,中高纬度西北太平洋出现正(负)的海温距平,表现为偏强(弱)的黑潮延伸体暖流影响我国东部沿海地区。2005年6月华南降水异常偏多对应半年前冬季赤道中太平洋出现假El Ni?o事件。2004年6月华南降水异常偏少,对应赤道中太平洋海温负异常和赤道东部与西部两端的海温正异常。

An analysis of high-resolution precipitation data for 1978--2006 indicates that the precipitation over southern China in June experienced a low-value period in 1980---1989 and a high-value period in 1992--2001. It also reveals that exceptional heavy （light） precipitation occurred in June 2005 （2004） since 1951. For these variations on both interdecadal and interannual timescales, fairly uniform anomalies of precipitation appeared over Vietnam, southern China, and southeastern China, surrounding the western edge of the South China Sea. Corresponding to positive （negative） precipitation anomalies, anomalous southeasterly （northwesterly） flow at 850 hPa reached Vietnam and anomalous southwesterly （northeasterly） flow expanded to the coastal regions of southern and southeastern China. Negative （positive） anomalies of sea surface temperature appeared over the extratropical northwestern Pacific in the winter and spring seasons before the positive （negative） precipitation anomalies during 1992--2001 （1980---1989）, associated with a strong （weak） extension of the warm Kuroshio Current that affects the coastal region of eastern China. The above-normal precipitation in June 2005 was associated with the La Nifia event in the previous winter, and the below-normal precipitation in June 2004 was associated with negative anomalies of sea surface temperature over the equatorial central Pacific and positive anomalies over the equatorial western and eastern Pacific.