南北半球高低层环流切变与长江流域夏季降水异常的关系

RELATIONSHIP BETWEEN SUMMER RAINFALL IN THE YANGTZE RIVER AND SHEAR OF CIRCULATION ON 850HPA AND 200HPA OVER SOUTH AND NORTH HEMISPHERES

利用奇异值分解 (SVD)方法分析和讨论了夏季 85 0hPa和 2 0 0hPa高低层纬向风距平差与我国夏季降水异常的关系 ,发现澳大利亚东北部高低层纬向风切变与长江中下游地区降水有较好的反相关 ,并定义了澳大利亚季风指数。 9个澳大利亚冬季风 (南半球 )指数低值年与 7个高值年我国夏季降水的平均差值图表明 ,显著的降水差异出现在长江中下游 ,低值年有利于长江中下游地区降水偏多 ;澳大利亚冬季风指数与夏季北半球 5 0 0hPa高度场的相关图在东亚至西太平洋的相关分布呈现出“ - + -”结构 ,在我国长江以南的中低纬和贝加尔湖的高纬地区是负相关区 ,正相关在我国北方至日本的中纬地区。

The relationship between summer rainfall over China and the shear of zonal wind at 850 hPa and 200 hPa was analyzed by the method of SVD. Result shows a good relation between summer rainfall in the reaches of the Yangtze River and the shear of zonal wind at 850 hPa and 200 hPa over the northeast of Australian. The Australian monsoon index was defined as I_ AM. The distribution of rainfall difference between the 9 high I_ AM years and 7 low I_ AM years shows that the most significant difference occurs over the reaches of the Yangtze River. In the low (high) I_ AM years, summer precipitation is more (less), I_ AM also shows a notable relationship with 500 hPa geopotential height over the north hemisphere.