近57a南疆帕米尔地区春季降水季节内差异及环流异常分析

Analysis of Intraseasonal Variation of Spring Precipitation and Its Related Atmospheric Circulation Anomalies during Recent 57 Years in Pamirs,Southern Xinjiang,China

基于1961—2017年帕米尔地区3站的日降水资料及NECP/NCAR再分析资料,利用气候诊断分析及多元统计学方法,研究了近57 a来帕米尔地区春季降水特征及季节内差异,并讨论了降水偏多年大气环流异常特征。研究表明:(1)近57 a来,帕米尔地区季节尺度上和月尺度上降水增加明显,旬尺度上有不显著的增加趋势。21世纪初帕米尔地区进入新的多雨期,降水正距平年份强度和频率均有显著增加。(2)500 hPa高度场上3月东欧沿岸脊发展、东欧—西西伯利亚槽加深,4—5月欧洲沿岸槽加深、乌拉尔山脊发展、巴尔喀什湖槽加深是帕米尔地区降水异常偏多的关键系统及指标。(3)降水异常年的高空急流较常年强度更强、位置更偏东,在旬尺度上是一个逐渐减弱西退的过程;其低层风场距平分为西南风距平辐合型、西南风和东北风距平辐合型和气旋式环流距平辐合型,均有利于低层辐合。(4)降水异常偏多年水汽输送以偏西路径为主,同时还有偏东、西南和偏南路径,水汽辐合强度较常年更强,更有利于降水的产生。

The intraseasonal variation of anomalies in Pamirs of China from 1961 spring precipitation and its related atmospheric circulation to 2017 were analyzed combining the climate diagnostic analysis and multi-variables statistic methods based on daily mean precipitation data from meteorological stations and daily NCEP/NCAR reanalysis data. Results showed that： （1） In recent 57 years, there was an obvious increasing trends in seasonal and monthly precipitation, but not significant in ten day scales. And a new pluvial period was begin in early 2010s, the intensity and frequency of rainy years increased significantly. （2） The key indicators and systems of pluvial year in Pamirs included developing of the eastern European coastal ridge, deepening of the Eastern Europe- Western Siberia Trough at March, and developing of the Ural Ridge, deepening of the Eastern European Costal Trough and Balkhash Lake Trough. （3） The high level jet in anomalous precipitation years was stronger and more easterly than normal, it was gradually weaking of west retreat on the tenth scale precipitations. The low level jets anomaly was divided into southwest wind anomaly convergence type, southwesterly wind anomaly convergence type, and cyclonic anomaly convergence anomaly, which were all favorable for the convergence in low-level to generate rainfall. （4） The water vapor transport paths in anomaly precipitation years was mainly west-oriented, also with the eastern, southwest, southerly paths. And the water vapor convergence intensity was stronger than the normal, which was more conducive to the spring precipitation in the Pamirs.