山西省夏季年际气候异常研究1.山西省一致多雨或少雨型

利用美国国家环境预报中心(NCEP)再分析资料以及山西64个测站的月降水量等资料,采用EOF分解和合成分析方法研究了1960-2003年山西夏季降水的年际变化异常以及时空特征.利用EOF方法分析山西夏季降水,第一类雨型是山西省夏季一致多雨型,并给出此类异常雨型的时空分布和相应的典型年份.山西省夏季降水趋势分析表明,自1960年以来山西省夏季降水趋于减少.从500hPa位势高度场、纬向风、850hPa风场、700hPa水汽场、海温场等物理量场分析表明,山西夏季一致多雨年对应偏强的东亚夏季风,一般出现在La Nina事件(冷水事件)发生的当年和El Nino事件(暖水事件)发生的来年,中高纬度地区易出现纬向排列的 - -环流异常纬向分布型,大陆地区为一个异常槽和两个异常脊,乌拉尔山以东地区和鄂霍次克海是异常高压脊,而贝加尔湖地区是一个异常低压槽.山西省夏季一致少雨年对应偏弱的东亚夏季风,一般出现在El Nino事件(暖水事件)发生的当年和La Nina事件(冷水事件)发生的来年,与一致多雨年相反,中高纬度地区通常呈现纬向排列的- - 环流异常纬向分布型,大陆地区出现两个异常槽和一个异常脊.山西省夏季第一类雨型的发生与中高纬度地区纬向排列的环流异常分布和赤道太平洋海温异常有关系.

On Shanxi Summer Interannual Climate Change I. Concurrent Rich/Seldom Rainfall Pattern

Using American National Centre of Environmental Prediction reanalysis data and monthly precipitation data at 64 observational stations of Shanxi Province,the precipitation and temperature anomalies variation and temporal/spatial distribution patterns in 1960-2003 summer was studied with EOF,wavelet analyses and composite analyses methods.The first rainfall pattern over Shanxi Province was concurrent rich/seldom rain pattern.The distinctive years were selected and the corresponding spatial distributions were made out.Summer precipitation trends appeared the same trend pattern with the first rainfall pattern and showed that precipitation in 43 years decreased mainly over whole Shanxi Province.With the first rainfall pattern,analyzed were the general circulation anomalies and meridional winds on 500hPa potential height field,850hPa wind vector anomalous fields,700hPa water vapor field and sea surface temperature anomalies and so on.The results showed that concurrent rich rainfall pattern in Shanxi Province corresponded to strong East Asian summer monsoon,normally appeared at the year when La Nina event was happening and El Nino event had happened during last winter.While at mid-and high-latitudes there was latitudinal - -anomalous circulation pattern,and over Asian continent there were one trough around Baikal and two ridges around Ural Mountain and Okhotsk Sea respectively.Concurrent poor rainfall pattern corresponded to weak East Asian summer monsoon,normally appeared at the year when El Nino event was happening and La Nina event had happened during last winter.At the same time,at mid-and high-latitudes there was latitudinal- - anomalous circulation pattern,and over Asian continent there were two troughs and one ridge.Therefore,The first rainfall pattern in Shanxi Province is strong related to the anomalous latitudinal wave train happened at mid-and high-latitudes and SSTA over the equatorial Pacific Ocean.