新疆夏季降水的环流差异分析

Analysis on the Circulation Differences of Summer Rainfall over Xinjiang

基于1961—2015年夏季6—8月NCEP/NCAR再分析数据和新疆81站逐月降水数据,分析了北疆和南疆夏季降水协同变化和单独变化时的环流差异。结果表明,当新疆夏季降水整体偏多时,中亚上空的异常气旋将阿拉伯海的水汽输送至新疆,西亚副热带急流位置南偏。当南疆夏季降水偏多,北疆夏季降水偏少时,中亚异常气旋南偏,至40°N以南,水汽由阿拉伯海和西北太平洋输送至南疆,急流位置南偏。当北疆夏季降水偏多,南疆夏季降水偏少时,中亚为异常的反气旋,北疆上空存在异常的气旋式切变,水汽由西北太平洋输送至北疆,急流位置北偏,强度加强。当南疆(北疆)夏季降水单独偏多时,中亚40°N以南为异常气旋(反气旋),以北为异常反气旋(气旋),急流位置南偏,水汽由阿拉伯海输送至南疆(北疆)。

Based on observed rainfall data of 81 stations in Xinjiang and the NCEP/NCAR reanalysis data during 1961-2015,the concurrent and individual variations of summer rainfall related to thermal circulation difference between southern and northern Xinjiang are analyzed.The results show that when the summer rainfall both over southern Xinjiang and northern Xinjiang is positive,the water vapor is transported from the Arabian Sea by anomalous cyclone over Central Asia,corresponding to the subtropical westerly jet in Western Asia shifting further south.When the summer rainfall in southern Xinjiang is positive and the summer rainfall in northern Xinjiang is negative,the anomalous cyclone in Central Asia moves southward to 40°N,and the water vapor is transported from Arabian Sea and northwest Pacific,corresponding to the subtropical westerly jet over Western Asia shifting further south.When the summer rainfall over northern Xinjiang is positive and the summer rainfall over south Xinjiang is negative,anomalous anticyclone exiting over Central Asia,anomalous cyclone exiting over Xinjiang and the water vapor is transported from northwest Pacific,corresponding to the intensity of subtropical westerly jet over Western Asia strengthened.When the summer rainfall over individual southern(northern)Xinjiang is positive,anomalous cyclone exiting over south(north)Central Asia and north(south)Central Asia,respectively,corresponding to the subtropical westerly jet over Western Asia shifting further south,and the water vapor is transported from Arabian Sea.