盛夏西太平洋副热带高压对陕西降水的影响

Impacts of Western Pacific Subtropical High on Mid-summer Precipitation in Shaanxi Province

利用1961-2008年陕西78个气象站7-8月降水资料、西太平洋副高逐月指数资料及500hPa位势高度场和700hPa风场月平均再分析资料,通过相关、回归分析、小波凝聚谱分析等方法探讨盛夏西太平洋副热带高压对陕西降水的影响及机制,为盛夏陕西降水的气候预测提供依据。结果表明,盛夏副高强度、脊线、西伸脊点指数与陕西降水关系密切,副高偏强偏西时陕西降水偏多,副高偏北时陕西北部降水偏多、南部偏少。8月副高3个指数与陕西降水的相关关系更为密切,通过显著性检验的站点明显增多。副高的强度和位置变化引起副热带和中高纬度大气环流的异常,进而影响陕西降水。8月副高偏强偏西时,巴尔喀什湖阻高增强,700hPa西南季风的水汽输送增强,陕西位于冷暖空气交汇区,降水偏多;副高偏南时,水汽辐合区位于陕南,陕西南部多雨、北部少雨;副高偏北时,水汽辐合区位于陕北,陕西北部多雨、南部少雨。8月副高强度指数与同月陕西降水的显著共振周期为7～8a,且副高强度变化超前于陕西降水变化1.26a,说明8月副高强度的年际变化是引起同月陕西降水年际变化的重要原因。

In order to provide evidence to precipitation prediction in Shaanxi province,the impacts of Western Pacific Subtropical High（WPSH） in mid-summer on precipitation in Shaanxi province and its mechanism was analyzed by using of correlation analysis,regression analysis and wavelet coherence spectra analysis,based on precipitation data collected from 78 meteorological stations in Shaanxi province,monthly WPSH indices data provided,monthly reanalysis datasets about 500hPa geopotential height and 700hPa wind field from July to August from 1961 to 2008.The results showed that there was correlation among precipitation and the intensity,ridgeline location,western extension ridge point of the WPSH.The rainfall was more than normal when WPSH was strong and further west,when WPSH was located further north than normal,precipitation was more than normal in northern Shaanxi and less in southwestern.The three indices of WPSH in August had more close relationship with precipitation,and the numbers of stations which passed significance test were obviously increased.Anomalous atmospheric circulation in subtropics and mid-high latitudes was caused by the intensity and location variation of WPSH,which influenced precipitation in Shaanxi province further more.When WPSH was stronger and further west,the Balkhash Lake Block and 700hPa summer monsoon strengthened,Shaanxi province was located the confluence of cold and warm air,and precipitation would be higher.However,when the WPSH moved toward south,water vapor convergence zone located in southern Shaanxi,and vice versa.There was a remarkable resonance cycle of 7-8 years between the high-intensity index of WPSH and precipitation in Shaanxi in August,and the intensity index of WPSH ahead of the precipitation changes 1.26 years,which indicated that annual precipitation variation in Shaanxi mainly caused by WPSH annual intensity variation.