近40年来塔什干低涡活动特征的统计分析

Statistical Analysis on Activity Characteristic of Tashkent Vortex in Last 40 Years

利用1971—2010年NCEP/NCAR逐日再分析资料,根据塔什干低涡定义,分析了塔什干低涡的时空分布特征、移动路径及其对南疆天气的影响。结果表明:(1)1971—2010年,塔什干低涡过程平均每年出现7.95次,成熟期生命史平均为3.1天,4天以上的仅有13.5%;(2)4—6月和9—10月是塔什干低涡活动的两个高峰期,其中5月出现次数最多,其次是10月和6月;(3)塔什干低涡频次的年代际变化呈抛物线型,1970-1980年代由78次增加到83次,之后逐渐减少,年低涡频次存在7年左右的显著振荡周期,同时具有13年的次振荡周期;(4)塔什干低涡活动有两个高频中心,分别位于67.5°E,40.0°N和72.5°E,35.0°N,移动路径以偏东方向为主,占84%,西退塔什干低涡仅有5.7%;造成南疆显著降水天气的塔什干低涡占其总数的23.3%,夏季此类低涡所占比例最高,达41.2%。

Based on the given definition,the characteristics of spatial and temporal distributions and moving track of Tashkent vortex in 1971-2010 were investigated using the NCEP/NCAR reanalysis data in 1971-2010.The analyzed results are as follows：（1） There are 7.95 times for Tashkent vortex process every year in 1971-2010.The average life of mature Tashkent vortex is 3.1 days,and only 13.5% lasting more than 4 days.（2） There are the two peak periods of Tashkent vortex in 4-6 and 9-10 months,and the biggest in May,then in October and June.（3） The interdecadal change of frequency of Tashkent vortex shows as parabola.Frequency of Tashkent vortex increases from 78 in 1970s to 83 in 1980s,then it decreases gradually after 1980s.Annual frequency change of Tashkent vortex has significant 7-year oscillation period,as well as the characteristic of 13-year sub-oscillation period.（4） There are two high-frequency regions,one is 67.5°E,40.0°N,the other is 72.5°E,35.0°N.The moving path of Tashkent vortex is mainly to the east direction,and it reaches 84% of the total.At the same time,the moving westward from Tashkent vortex is 5.7%.The rate of precipitation-vortex is 23.3%,which is highest in summer（41.2%）.