新疆夏季降水异常的时空特征及北极涡与阻塞高压对其的影响

采用新疆地区50个站1960-2000年6～8月降水资料,运用标准化距平、二项式系数加权平均、Morlet小波分析及线性倾向估计等方法分析了新疆夏季降水异常的时空特征,并基于NCEP/NCAR的500hPa再分析高度场资料对极涡、阻高与新疆夏季降水做奇异值分解,从而讨论了极涡与阻高对新疆夏季降水的影响,得到了一些结果。新疆夏季降水具有明显的空间不均匀性,天山山脉附近的降水量最大,而南疆的塔克拉玛干沙漠周边及新疆东部戈壁滩地区的降水量最小。新疆夏季降水存在明显的年际差异,20世纪80年代初之前年际变化振幅较小,之后年际差异急剧增大。新疆夏季降水的年代际变化、周期性也很显著,降水量总体上呈现明显的线性增长趋势。同期及前期冬春季极涡与阻高对新疆夏季降水均有重要影响。

Space-time features of summer rainfall anomaly of Xinjiang and the effect of North Polar Vortex and blocking

With standard deviation,binomial coefficient smooth,Morlet wavelet analysis and linear trend estimate,the anomaly space-time characteristics are analysed with the observed data of precipitation(June-August)at 50 stations in Xinjiang from 1960 to 2000.Based upon NCEP/NCAR reanalysis monthly mean geopotential height data at 500hPa,the effect of northern polar vortex and blocking on summer precipitation over Xinjiang is discussed by means of singular value decomposition.The result shows that the distribution of summer precipitation in Xinjiang is obviously asymmetric.The maximum lies in Tianshan mountains,but the minimum locates nearby the grand Taklimakan Desert and the Gobi in east Xinjiang.The summer precipitation exists evident inter-annual variation.Before 1980s,the variation extent of summer mean precipitation is little,but it is contrary after that.It is found that the precipitation also has distinct inter-decadal variation,periodicity and trend.The overall precipitation trends to increase linearly as a whole.Polar vortex and blocking during summer and last winter-spring play important role in summer precipitation in Xinjiang.