晋北地区秋季降水异常的时空分布及环流特征分析

Analysis of Temporal Spatial Features and Circulation Characteristics of Autumn Precipitation In Northern Shanxi

利用美国国家环境预报中心（NCEP）再分析资料以及晋北地区18个台站1960—2008年秋季降水资料，通过M—K突变曲线、滑动t检验法以及累积距平法检验方法，对晋北地区秋季降水进行了检验分析；并利用合成分析方法，对晋北秋季多雨、少雨年的大气环流异常特征进行了分析。结果表明：（1）晋北地区秋季降水在1967年前后和2003年发生了由少到多和由多到少的转折；秋季降水量线性趋势西南部为负值，东北部大同、浑源、广灵、灵丘、朔州、繁峙、五寨线性为正值，负趋势的台站多于正趋势台站，降水有减少的趋势。（2）多雨年中高纬度，500hPa呈现“东高西低”的分布特征，在乌拉尔山以东至贝加尔湖以西一带有低压槽加强，晋北地区处于低槽的东南侧，冷暖空气多交汇于山西一带，因而造成秋季多雨天气；少雨年巴湖附近的低压槽位置偏西偏南，而高压脊位于贝湖的北部，不利于降水的产生。（3）对流层低层流场多雨年西北太平洋有暖湿气流向北输送，与鄂霍次克海回流下来的弱冷空气在贝湖及华北一带交汇，有利于降水；少雨年虽西太平洋有暖湿气流向北输送，但冷空气势力较弱，不利于降水的产生。

Based on NECP reanalysis data and the observational data fron18 stations in Northern Shanxi during 1960-2008 , by using the linear t rend analysis , M-K sudden change test , t-test and other ethods , the statistic analysis shows that the autumn precipitations turn from less to more and more to less in 1967 and 2003.The autumn precipitation linear trend was negative in southwest , the linear trend was positive in the Northeast of Shanxi. The negative trend stations was more , the precipitation trend was decreasing, by composite analyzing the abnormal atmospheric circulation character of rainy and drier years in northern Shanxi , It showed that the 500hPa geopotential height have ＂east high west low＂ distribution characteristics In rainy years of autumn , From the east of the Ural Mountains to the west of Lake Baikal, the trough of low pressure was strengthen. Northern Shanxi was in the southeast side of the trough. The cold air and the warm air intersect in Shanxi area resulting rainy weather in autumn, the trough of low pressure was south and west in drier years. The ridge of high pressure was in the north of the lake , which was not conducive to the autumn precipitation in northern Shanxi. The warm and humid air transport from west Pacific to the north in drier years, but the forces of cold air was weak and without a good trigger mechanism , so it was not good for raining .