东中国海夏季潜热通量的时空特征及其与中国东部降水的联系

Temporal and Spatial Characteristics of Latent Heat Flux in the East China Sea and Its Association with Summer Rainfall in East China

利用1985—2006年OAflux、NCEP/NCAR再分析资料和中国大陆东部的120个测站降水资料,应用EOF分解和线性回归等方法分析了东中国海夏季海气热通量时空特征及其与中国东部夏季降水的关系。结果表明,东中国海夏季潜热通量EOF1模态空间场的强信号区为黄海、东海至台湾海峡和南海北部局部海域,时间系数(PC1)表现出显著的年际变化和1997年前后的突变。降水和经向环流的PC1回归分析还表明,夏季潜热通量的异常变化与中国东部降水和经向环流的变化密切相关,潜热通量正异常对应黄淮地区和华南地区的上升气流正异常,降水偏多,而东北与华北地区为下沉气流正异常,降水偏少。1997年前后东中国海潜热通量发生突变之后呈明显的上升增强趋势,使得上述现象更为显著,即:对应东中国海夏季潜热通量的正异常,黄淮地区和华南地区为上升气流正异常,降水偏多;东北地区和华北地区为下沉气流正异常,降水偏少。这表明夏季东中国海及邻近海域潜热通量的异常变化是导致中国东部汛期降水年际和年代际异常的重要原因之一。

Based on the OAFLUX,the NCEP/NCAR reanalysis data for the period of 1985-2006 and the observed precipitation data at 120 observational stations of East China,the temporal and spatial characteristics of sea-air heat fluxes in the East China Sea and its association with summer rainfall in East China are analyzed by using the Empirical Orthogonal Function（EOF） and the Linear Regression Analysis methods.The analyzed results show that the spatial pattern of EOF1 mode of latent heat flux displays strong signal in the Yellow sea,East China Sea,Taiwan Strait and the regional parts of northern South China Sea.Furthermore,the corresponding to time coefficient of EOF1（PC1） indicates significant interannual variation and a climatic shift in 1997.In this paper,the regression patterns of the meridional circulation and summer rainfall with respect to PC1 show that the abnormal change of latent heat flux in summer has a close relation with the change of summer rainfall and meridional circulation.In contrast to the situation in North China and Northeast China,as latent heat flux anomaly in East China Sea is positive,the meridional circulation will be manifested as updraft anomaly in the regions of Yellow River-Huai River valleies and South China,which may result in summer rainfall.The above phenomena exhibit prominent after the climatic jumping in 1997,i.e.,as latent heat flux anomaly in the East China Sea is positive,the meridional circulation will be manifested as updraft anomaly in the region of Yellow River-Huai River valleies and South China and the summer rainfall anomaly is also positive,and that is opposite to North China and Northeast China.It is suggested that the abnormal change of latent heat flux in the East China Sea and its adjacent sea area is one of the most important reasons for the abnormal of summer rainfall in East China on the interannual and interdecadal timescales.