热带环流指数与夏季长江中下游旱涝的年际变化

TROPICAL CIRCULATION INDEX AND ITS RELATION TO INTERANNUAL VARIATION OF YANGTZE FLOOD/DROUGHT

比较利用海—陆气压差和南亚季风环流定义的夏季风指数对夏季长江中下游旱涝年际变化的表征能力，根据影响东亚季风的主要热带环流定义了一个环流指数，该指数与长江中下游旱涝的年际变化存在很好的对应关系。利用１９８２年～１９９４年夏季平均可降水量距平、北半球５００ｈＰａ位势高度场距平，通过高、低指数合成和高度场与同期的热带海表温度异常的ＳＶＤ分析，结果表明，热带环流指数的高、低差异和年际变化对影响东亚夏季降水的大气环流型具有较强的分辨能力。

Summer monsoon index defined by land sea presure contrast is compared to that by south Asian monsoon circulation in characterizing the interannual variation of floods/droughts over the mid lower valleys of the Yangtze. In terms of principal tropical circulation of east Asian monsoon defined is the summer monsoon index that is found to reflect well the interannual variation in the flood/droughts. The study shows that the difference in both higher and low index and the interannual variation has higher ability to identify the pattern of atmospheric circulation related to east Asian summer rainfall through the use of the index compositing and SVD analysis of northern 500 hPa height and synchronous SSTA at tropics in the context of 1982～1994 mean precipitation (precipitable water) and the 500 hPa height anomalies.