中文摘要：

利用1958—2014年夏季NCEP/NCAR大气环流资料和中国486站降水观测资料,通过多种统计诊断方法,从与夏季中国东部3类不同雨型分布相联系的东亚高低层风场变化特征出发,依据与雨带变化密切联系的高层200 hPa纬向风定义了一个新的东亚副热带夏季风指数。分析表明,该指数不仅能反映夏季东亚大气环流的变化特征,兼顾北方冷空气活动和南方东亚夏季风环流变化,同时还能反映夏季中国东部降水南北差异的年际特征。强东亚副热带夏季风指数年,高层中纬度西风急流位置偏北,低层西太平洋副热带高压偏强偏北,有利于冷空气活动位置偏北和东亚东部西南暖湿气流向北推进,中国东部多以Ⅰ类雨型为主;弱东亚副热带夏季风指数年的环流变化刚好相反,中国东部多以Ⅲ类雨型为主。与现有东亚夏季风指数的对比分析表明,该指数在反映中国东部南北区域降水变化的差异方面有很大改进。

英文摘要：

Based on precipitation data collected at 486 observational stations in China and NCEP / NCAR reanalysis atmospheric circulation data from 1958 to 2014, the relationship between summer precipitation in China and winds at low and high levels is investigated first. A new East Asian subtropical summer monsoon index is then defined using 200 hPa zonal winds that are closely related to three types of summer rainfall pattern in eastern China. The results show that the new index can well reflect not only the integrated impact of circulations over the high and low latitudes, but also the characteristics of summer precipitati- on difference between northern and southern China. In strong East Asian summer monsoon years, the upper westerly jet strengthens, cold air activity is located to the north, the low-level West Pacific subtropical high intensifies and shifts north- ward, resulting in strong southwesterly flows over eastern East Asian, and pattern I rainfall occurs in eastern China; the cir- culation pattern in weak East Asian summer monsoon years is opposite to that in strong monsoon years, and pattern Ⅲ rainfall occurs in eastern China. Compared with the existing East Asian summer monsoon indices, the new index has a great advantage in reflecting the precipitation difference between the north and south of eastern China.