一种改进的华西秋雨指数及其气候特征

利用1960～2011年中国601站9～10月逐日降水量、日照时数资料，针对他人提出的华西秋雨指数，并结合华西秋雨的天气气候特征，改进建立了一种新的华西秋雨指数，并与他人提出的指数做了对比分析。结果表明：改进的华西秋雨指数能够相对更好的反映华西秋雨易发地区的地理分布及其强度变化，更准确地表征华西秋雨的年际、年代际变化特征；利用新指数发现华西秋雨的全区一致性特征明显，并呈现准6年周期的年际变化，其年代际变化特征明显，1960年代到1970年代初，1980年代到1990年代初偏强，1970年代中后期和1990年代后期偏弱，进入21世纪，呈现出由弱转强的趋势。

Improved Index and Climatological Characteristics of the Autumn Rain in Western China

After analyzing the daily precipitation and sunshine duration data from September to October of 1960-2011 from 601 stations in China, a new autumn rain index was proposed by comparing it with the autumn rain indices presented by others, and combining the weather and climatological characteristics of autumn rain in western China. We also examined the proposed index by using high-resolution empirical orthogonal function (EOF) analysis. The results suggest that the modified autumn rain index better describes the geographical distribution and variations in autumn rain intensity, as well the interannual and interdecadal characteristics of autumn rain in western China. The application of the new index also suggests that autumn rain is consistent throughout western China. According to the power spectrum, the autumn rain index exhibits a quasi 6-year oscillation on the interannual timescale and pronounced interdecadal variations. In western China, the autumn rainfall was above normal during the 1960s to early 1970s and 1980s to early 1990s, whereas there was less rainfall in the mid to late 1970s, the late 1990s, and in the early 21st century. However, the autumn rainfall in western China has been increasing since the mid 2000s.