中文摘要：

在综合考虑了东亚夏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东亚副热带夏季风指数,并利用1948—2007年NCEP/NCAR再分析资料分析了近60年来东亚副热带夏季风的变化特征。研究表明：该指数可以很好地反映东亚副热带夏季风的季节变动、年际变化、年代际变化等特征。另外,该指数与我国160个测站降水的相关分析表明：高指数年,夏季季风强,华北、西南内陆及华南沿海地区多雨,江淮地区少雨; 反之,低指数年,夏季季风弱,华北、西南内陆及华南沿海地区偏旱,江淮流域偏涝。最后,通过与其它四种有代表性的指数的对比,发现本指数在指示江淮夏季降水方面具有明显的优势。

英文摘要：

Based on synthetically calculated thermodynamic and kinetic features of the summer monsoon of East Asia, this article utilizes the moist potential vorticity （MPV） to define a new index of subtropical summer monsoon for this region, and uses the NCEP/NCAR data to analyze the variation features of the subtropical summer monsoon for the past 60 years. The result shows that this new index can well reflect the seasonal, interannual, interdecadal variations and abrupt climate change of the subtropical summer monsoon. Besides, correlation analysis of this new index and the data of 160 stations in China show that, in the high index year, the summer monsoon is strong, it rains more in North China and southwestern inland and South China＇s coastal areas while it rains less in the areas near Changjiang River and Huaihe River; the opposite is true in the low index year. Lastly, through comparisons with the other four representative indexes, this new index has obvious advantages in denoting the summer rainfall in the areas near Changjiang River and Huaihe River.