Interannual and interdecadal variations of moisture transport by Asian summer monsoon and their association with droughts or floods in China
CHEN Ji-Long, HUANG Rong-HuiCenter for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100080, China
The NCEP/NCAR reanalysis data (NCEP-R1) and the ECMWF reanalysis data (ERA-40) for the period of 1958～2002 are used to estimate interannual and interdecadal variations of vertically integrated moisture transport (VIMT) by Asian summer monsoon (ASM) and investigate their association with summer rainfall anomalies based on monthly precipitation at 160 stations in China. The results show that both VIMT by ASM and summer rainfall in China exhibit obvious biennial rhythms as revealed by time coefficient of the leading EOF mode. When summer VIMT is strong (weak) in the south Asia monsoon region, a dipole VIMT anomaly in the East Asia—western North Pacific is propitious to negative (positive) VIMT convergence anomalies in the middle and lower reaches of the Yangtze River and the Yangtze-Huaihe valley but positive (negative) VIMT convergence anomalies in South China and North China, which result in a meridional tripole structure of rainfall anomalies in eastern China, i.e., droughts (floods) in the middle and lower reaches of the Yangtze River and the Yangtze-Huaihe valley but floods (droughts) in South China and North China. On interdecadal scale, persistent floods in the middle and lower reaches of the Yangtze River but persistent droughts in South China and North China are mainly linked with weakening of VIMT by ASM and a dipole VIMT anomaly in the western North Pacific after the end of 1970s. In view of the in-phase relationship between summer rainfall anomalies and VIMT convergence anomalies in China, the analysed results also show interannual and interdecadal variations of VIMT by ASM can be better described by the ERA-40 reanalysis than the NCEP-R1 reanalysis.
【Fund】： 国家重点基础研究发展规划项目(2006CB403600);; 国家自然科学基金项目(40705034 40725016);; 中国科学院知识创新工程领域前沿项目(IAP07118)资助
【CateGory Index】： P46
【CateGory Index】： P46