分段副热带高压位置指数的建立及应用

Establishment and Application of the West and East WPSH Meridional Indices

由于西太平洋副热带高压(简称副高)东西部分的经向位置对我国气候有着不同影响,定义了西段、东段副高位置指数:分别为10°~60°N、110°~130°E和10°~60°N、130°~150°E范围内子午线上500 hPa位势高度最大值所在的平均纬度,并将两者平均值定义为副高中心位置指数。这些指数与我国东部夏季降水的相关性较业务副高脊线指数有所提高,尤其是西段副高位置指数与华北平原夏季降水的正相关关系,同时副高位置指数基本维持了业务副高脊线指数与长江流域降水的负相关关系和与华南降水的正相关关系。西段副高位置指数偏北时,对应西北太平洋上500 hPa出现反气旋环流,反气旋中心位于38°N、130°E附近;而东段副高位置指数偏北对应的反气旋中心位置偏东偏北,位于40°N、145°E附近。此外,西段、东段副高位置指数偏南、偏北的不同配置对应我国雨带分布的四种类型。分段副高位置指数与我国夏季降水年际变化较好的相关性将为降水季节预测和季节内雨带移动的研究提供更多的指示意义。

Since the meridional positions of the east and west part of western Pacific subtropical high(WPSH)affect the climate over China differently,we redefined the meridional index of WPSH in this study.The mean latitude of the location of 500 hPa geopotential height maximum along several meridian in 10°-60°N,110°-130°E and 10°-60°N,130°-150°E is defined as new west index(Index_NEW_west)and new east index(Index_NEW_east),respectively.Their average value is defined as new meridional index of WPSH(Index_NEW).The correlation between these indices and summer precipitation over eastern China is more significant than the ridge index defined by National Climate Centre(Index_NCC),specifically for the positive correlation between Index_NEW_west and precipitation over North China Plain.The negative correlation between Index_NEW_east and precipitation over Yangtze River Basin is similar to that of Index_NCC.Regression of the 500 hPa horizontal wind with respect to Index_NEW_west(Index_NEW_east)presents anticyclonic circulation over western North Pacific and the anticyclone center locates near 38°N,130°E(40°N,145°E).The various collocations between north/south anomalies of Index_NEW_west/Index_NEW_east correspond to four types of rainfall patterns.The good relationship between the interannual variation of new indices and summer precipitation over eastern China could provide more valuable references for the study of precipitation prediction and interseasonal movement of rainfall band.