用湿位涡定义的印度夏季风指数及其与中国气候的关系  

MOIST POTENTIAL VORTICITY INDEX OF INDIAN MONSOON AND ITS RELATIONSHIP WITH CLIMATE IN CHINA

作　　者：徐忠峰[1] 钱永甫[1] 

机构地区：[1]南京大学大气科学系,南京210093

出　　处：《气象学报》2006年第6期760-769,共10页Acta Meteorologica Sinica

基　　金：国家自然科学基金重点项目(40233037);国家重点基础研究发展计划(973)项目:"我国南方致洪暴雨监测与预测的理论和方法研究(2004CB418300)"

摘　　要：印度季风区是世界上季风现象最显著的地区,伴随着夏季风爆发和撤退,季风区的大气风场和湿度场都存在明显的季节转换,这种季节转换可以作为区分夏季风与冬季风的一个很好的标准。以往的季风指数大多只考虑了季风区的动力场或热力场的演变特征。在综合考虑了印度季风的热力和动力特征的基础上,利用湿位涡定义了一个新的印度夏季风指数。湿位涡是一个动力学和热力学的综合量,它既反映了风场的涡旋状况又反映了大气的垂直稳定度。研究表明:该指数可以很好地反映季风区大气热力场和动力场的季节演变特征。用湿位涡定义的印度夏季风指数不仅稳定而且可以较好地反映夏季风爆发时间、季风强度及季风的活跃与中断等多种特征。与以往的环流指数相比,湿位涡季风指数描述季风爆发时间的能力有较明显的改进。此外,该指数还可以很好地反映印度夏季降水的年际演变特征。初步的相关分析表明:印度夏季风爆发时间与中国西北及华北地区夏季降水呈负相关,与次年长江中下游以南地区夏季气温也存在显著的负相关。此外,印度夏季风平均强度与前期华南地区春季降水也有密切关系。The most striking, typical monsoon climate in the world exists in South Asia. With the onset and withdrawal of the Indian summer monsoon, the wind and moisture fields generally show abruptly seasonal transitions, which can be taken as criteria to distinguish the summer monsoon from the winter monsoon. As for various existed monsoon indices, each index only considers an evolutional characteristic of dynamic or thermodynamic field of the Indian monsoon area. On the basis of the analyses of the dynamic and thermodynamic characteristics of the Indian summer monsoon using the NCEP/NCAR daily reanalysis dataset in 1958 - 1997, a new Indian summer monsoon index, moist potential vorticity monsoon index, Ipj, is defined by ρ^-1ξ·∨e, and it is able to simultaneously reflect both the dynamic （rotational flow filed） and thermodynamic （vertical stability） characteristics of the atmosphere. The research results show that Ipj reveals the seasonal variation characters of the stream and humidity fields in the Indian monsoon region very well. It is also found that Ipj is robust in describing monsoon onset date, seasonal intensity and active-break transition of the monsoon. Ipj is evidently superior to the previous monsoon circulation indices in describing the onset date of Indian summer monsoon, and furthermore, the Indian summer monsoon average intensity, Ia, shows a closer relationship with the all Indian summer rainfall. The correlation analysis also shows that the onset date of Indian summer monsoon determined by Ipj is significantly positively correlated with the summer rainfall in North China and Northwest China, and negatively with the next summer temperature in the south of the middle-low reaches of the Yangtze River. Besides, Ia also bears a significant relationship with the preceding spring rainfall in South China.

关 键 词：印度季风 湿位势涡度 季风指数 中国气候 相关分析 

分 类 号：P426[天文地球—大气科学及气象学]