1961—2018年九江夏季降水的年际变化特征及其可能原因

Interannual Variation Characteristics of Summer Precipitation in Jiujiang from 1961 to 2018 and Its Possible Causes

采用1961—2018年中国160站降水资料、NOAA海面温度资料及NCEP/NCAR再分析资料,利用回归分析等方法,对九江夏季降水的年际变化特征及其可能原因进行分析。结果表明:九江夏季降水具有明显的年际变化特征,存在准4a的变化周期;九江夏季降水与中国105°E以东的长江中下游及以南地区夏季降水呈显著正相关关系;中国邻近海域的西北太平洋(140°—150°E,15°—25°N)为影响九江夏季降水的海面温度关键区。西北太平洋海温异常与九江夏季降水异常的对应关系为:当西北太平洋夏季海温偏高时,西北太平洋副热带高压偏强偏南、贝加尔湖阻塞高压偏活跃、东亚副热带夏季风偏弱,长江中下游及以南有异常南、北风交汇,且水汽充沛、垂直运动旺盛。这种环流配置有利于长江中下游及以南地区包括九江的夏季降水偏多;反之亦然。

Based on the precipitation data of 160 stations in China, NOAA sea surface temperature data and NCEP/NCAR reanalysis data from 1961 to 2018, the interannual variation characteristics and possible causes of summer precipitation in Jiujiang are analyzed by the regression analysis and other methods. Results show that summer precipitation in Jiujiang presents obvious interannual variation characteristics, with a quasi-4-year variation period. There is a significant positive correlation between summer precipitation in Jiujiang and summer precipitation in the south area of the middle and lower reaches of the Yangtze River, east of 105°E. The Northwest Pacific Ocean (15°-25°N,140°-150°E) is the key area of sea surface temperature affecting summer precipitation in Jiujiang. The corresponding relationship between SSTA in the northwest Pacific and summer precipitation anomaly in Jiujiang can be summarized as follows:When SSTA in the northwest Pacific is higher in summer, the subtropical high in the northwest Pacific is stronger and further south, the blocking high in Lake Baikal is more active, the east Asian subtropical summer monsoon is weaker, and there is an anomalous convergence of south and north winds in the middle and lower reaches of the Yangtze River and south of the Yangtze River, where the water vapor is abundant and the vertical motion is vigorous. This circulation configuration is conducive to summer precipitation in the middle and lower reaches of the Yangtze River and south of the Yangtze River, including Jiujiang, and vice versa.