华南冬春降水的年际变化及其与水汽输送的联系

INTERANNUAL VARIABILITY OF WINTER AND SPRING PRECIPITATION IN SOUTH CHINA AND ITS RELATION TO MOISTURE TRANSPORT

利用1960—2008年华南47个基准站降水资料和NCEP/NCAR再分析资料,研究了华南冬春降水的年际变化特征及其与水汽输送的联系。结果表明,1960年代—1970年代和1990年代末至今,华南冬、春降水明显偏少。华南冬春降水异常以"全区冬春同号型"居多,且冬春连旱频率较高。影响华南冬春连续旱/涝的水汽输送存在季节性差异,冬季水汽输送变化主要来源于孟加拉湾和南海,春季水汽输送变化则来源于南海和我国北方。进一步探讨海温异常的影响发现,与华南冬春连续旱(涝)事件相关的Ni o3.4海温存在正、负异常型,海温异常中心分别偏向Ni o4(Ni o3)区和Ni o3(Ni o4)区。Ni o3.4区海温正异常时,孟加拉湾和南海水汽输送与华南冬春连续旱涝有密切联系;Ni o3.4区海温负异常时,冬季自西北太平洋经南海的水汽输送及春季自菲律宾海经南海的水汽输送和北方水汽输送对华南冬春连续旱涝有重要影响。以上水汽输送在两种海温异常情况下,连涝(旱)年均异常偏强(弱)。因此,Ni o3.4海温异常的变化及分布与华南冬春持续旱/涝事件存在联系,在此气候背景下,水汽输送异常是影响华南冬春降水异常的重要物理因子,其中南海是水汽输送异常显著相关区。

The interannual variability of winter and spring precipitation in SC and its relation to moisture transport are investigated by using the monthly precipitation data of National Meteorological Information Center（NMIC） and NCEP/NCAR reanalysis data from 1960 to 2008.The results show that winter and spring precipitation in SC is less than normal from the 1960s to the start of 1970s and from the end of 1990s to now.Most of rainfall anomalies on the regional scale of SC are well in phase during winter and spring and the frequency of persistent drought is more than that of persistent flood.Seasonal variations of the SC moisture transport differences between persistent drought and flood events are observed： the differences in winter are characterized by the moisture transport from the Bay of Bangle（BOB） and South China Sea（SCS）,while differences in spring are characterized by that from SCS and North China（NC）.There are two types of Ni？o3.4 sea surface temperature anomaly（SSTA） that are related to persistent winter and spring drought（flood） events in SC;one is positive SSTA following Ni？o4（Ni？o3） and the other is negative SSTA following Ni？o3（Ni？o4）.Moreover,the variations of moisture transport from BOB and SC have important effects on persistent drought/flood in SC with positive phase of Ni？o3.4 index,while that from western North Pacific-SC in winter and that from the Philippine Sea-SC and NC in spring primarily contribute to persistent drought/flood enevts in SC with negative phase of Ni？o3.4 index,and these stronger（weaker） moisture transports are observed in persistent flood（drought） during winter and spring regardless of the Ni？o3.4 index.In conclusion,with the correlation between the variations and distributions of Ni？o3.4 SSTA and persistent drought/flood events in SC,moisture transport is responsible for the formation of precipitation anomalies.In addition,the moisture transport from SCS is significantly correlated with persistent winter and spring drought/flood events.