山西省主汛期降水的特征研究

Precipitation characteristics in Flood season in Shanxi Province

以山西省1960-2005年逐日降水资料为基础,采用线性分析、小波分析等数理统计方法,分析46年来山西省主汛期降水及主汛期暴雨日数的变化特征,并利用NCEP日资料计算了影响山西区域的季风强度指数,综合研究结果表明:山西省的主汛期为7月上旬到8月中旬,这与季风在山西建立和撤退的多年平均日期是一致的,因而划分是较为科学的。山西大部分地区主汛期降水量均呈下降趋势,多年的变化趋势在0.1mm/10a～-30mm/10a之间,其中,中部的东部部分地区为显著下降趋势,通过了α=0.05的显著性检验。进入21世纪以后,山西主汛期降水虽然仍在减少,但暴雨的次数有所增加,说明气温升高后,降水量虽然趋于减少,但极端降水事件有增多的趋势。山西主汛期降水及主汛期暴雨的出现与季风强度有显著的正相关,当季风偏强(弱)时,山西省主汛期降水量偏多(少),主汛期暴雨站·次数偏多(少)。山西主汛期降水与7、8月份500hPa的位势高度场的相关分析表明,西太平洋副高偏强,贝湖至内蒙一带为异常低值区,中纬度环流呈东高西低的时候山西主汛期降水偏多。乌山阻高的建立有利于维持使山西主汛期降水偏多的环流形势。山西主汛期降水与7、8月份850hPa的经向风的相关表明当偏南异常气流深入我国东部北方大陆时,山西省主汛期多雨,这也是强夏季风年850hPa上的明显环流特征。

Based on observed daily precipitation data of 65 observation stations in Shanxi from 1960 to 2005,variable characteristics of precipitation and daily storm rainfall in main flood season were analysised.Results showed that mail flood season of Shanxi Province is from the first 10 days of July to the middle of August.Mean annual variable trend is in the range of 0.1mm--30mm every 10a.Main flood season precipitation of Shanxi is still decreasing,but frequency of storm is raising after the 21 century.Main flood season precipitation of Shanxi and occurrence of rain storm show positive correlation with the strength of monsoon.The correlation analysis of main flood season precipitation and 500hPa geopotential height of July and August show that when west pacific ocean subtropical anticyclone is strong the precipitation in the region between lake Bai and Inner Mongolia is abnormal lack,and when middle latitude circulation appears high,main flood season precipitation in east and low west Shanxi is abundant.