山西省夏季年际气候异常研究2．北少（多）南多（少）雨型

采用EOF分解和合成分析方法研究了1960-2003年山西夏季降水异常之北少(多)南多(少)型(第二类雨型)和山西省气温的变化异常.结果表明,两者具有较好的对应关系.分析了第二类异常雨型的时空分布,并给出相应的典型年份.EOF时间系数变化特征揭示了山西夏季降水第二类雨型有显著的年际振荡.利用合成分析,从500hPa位势高度场、纬向风、850hPa风场、700hPa水汽场和水汽输送场等物理量场研究了山西夏季第二类雨型的环流异常特征.结果表明,第二类雨型与弱的东亚夏季风相关联,北多南少和北少南多是弱夏季风的不同表现.山西省夏季降水北多南少年副高呈带状分布,位置偏北,强度较强;中高纬度地区异常波列呈大圆路径分布,在高纬度地区存在纬向排列的- -波列,同时在东亚大陆沿岸存在经向排列的- -波列.并且华北北部有西风异常,北支锋区偏北,由西南向东北水汽输送较强.北少南多年与之相反.海温场分析表明,第二类雨型与中北太平洋海温异常紧密相关.

On Shanxi Summer Inter-annual Climate Anomalies: 2. Seldom/Rich Rainfall in North/South and Rich/Seldom Rainfall in North/South Pattern

Using American National Centre of Environmental Prediction reanalysis data and monthly precipitation data at 64 observational stations of Shanxi Province,the summer rainfall an-omalies in1960-2003,that is the second rainfall pattern of rich/seldom in the north and seldom/rich in the south,and temperature anomalies variation were analyzed with EOF,wavelet analysis and composite analysis methods.The temperature linear trend indicated that warmer in the north and cooler in the south was well accordance to the seldom rainfall in the north and rich in the south from 1960 to 2003.The distinctive years of the second rainfall pattern were selected and the corresponding spatial and temporal distributions were made.The analysis was performed for the general circulation anomalies features with 500hPa potential height field,zonal winds,850hPa wind vector anomalous fields,700hPa water vapor field and water vapor transportation field.The results showed that the second rainfall pattern was closely related to weak East Asian summer monsoon and rich in the north or in the south were different appearances of weak monsoon.When the rich/poor rainfall in the north and poor/rich rainfall in the south pattern happened,the subtropical high was stronger/weaker and presented belt/block pattern,and there was westerly/easterly anomalies in north/south,which meant that the northern front region was located more north.And the water vapor transport from the southwest to the northeast was stronger/weaker too.When rainfall was rich in the north and seldom in the south,there was a wave train appearing big circle route at mid-and high-latitudes,while at high latitude the latitudinal wave train appeared- -anomalous circulation pattern and along the coast of East Asian continent- -anomalous circulation pattern too.Analysis of sea surface temperature showed that the second rainfall pattern has strong connection with Pacific SSTA at middle and high latitudes.