嘉兴夏季降水与副高的年际年代际变化关系分析

为了定量描述副高变化及其与嘉兴夏季降水的关系,在500 hPa高度场上选择一个特定的关键区定义了一个副高指数,分析发现该指数既存在大于45年周期、准9~16年的年代际变化周期,也存在4年和准2年的年际变化,与降水间存在很好的相关关系,可以作为预测降水的一个重要因子。嘉兴夏季降水与西北太平洋副热带高压在1980年前后发生了一次同期的年代际尺度跃变。1980年以前,副高强度明显偏弱,主体偏东,嘉兴夏季降水偏少;而1980年以后则反之。

Interannual and Interdecadal Variation of Relation between Summer Precipitation in Jiaxing and Subtropical High

In order to describe quantitatively the relation between subtropical high variation and summer precipitation in Jixing,a subtropical-high index is defined by selecting a specified key area on 500 hPa.The analysis of the index indicates that there existed very good relation between subtropical-high index and summer precipitation with interdecadal variation periods of more than 45 years and about 9 to 16 years,as well 4 years and quasi-2 years.The index can be used in operational precipitation forecasting.There occurred a synchronous interdecadal jump in summer precipitation in Jiaxing and Northwest Pacific Ocean tropical high around 1980.Before 1980,the tropical high intensity was weaker and farther eastern than normal,while the precipitation in Jiaxing was less than normal;and after 1980,vice versa.