引发新疆强降水的中亚气旋分析

Analysis of Central-Asia Cyclone With Intense Precipitation in Xinjiang

利用常规观测、地面加密观测、风云二号气象卫星水汽云图等资料,统计分析了20142018年给新疆造成强降水的中亚气旋的特征,归纳了中亚气旋的概念模型。结果表明:在新疆115次强降水过程中,有24次伴有中亚气旋。中亚气旋主要发生在北疆及其周边地区,以巴尔喀什湖及其附近地区最多,而南疆盆地较少。从时间分布来看,中亚气旋在夏季-初秋较多、春季和冬季较少。6、8、9月最多,各为5次;而3、10、12月一次也没有。移动方向为东移或东北移,且移速快。水汽云图上主要表现为逗点云系或斜压叶状云系。大多数气旋强度为1000~1010 hPa,强度较弱。17次中亚气旋发生在高空急流出口区的左侧,7次在高空急流入口的右侧。虽然中亚气旋强度不强,但其生成和发展时均伴有高空辐散。与中亚气旋相伴的强降水先发生在暖区,然后是气旋和冷锋或暖锋共同作用产生降水。中亚气旋为浅薄的斜压系统。在“东高西低”的形势下,中低层低涡、切变线,以及低涡东侧的偏南风和偏东风水汽输送等均有利于强降水产生。中亚气旋中三条输送带的特征是:从近地层暖区上升的偏南暖湿空气沿锋面爬升到对流层上层形成了暖输送带,而从地面气旋东侧、东路冷空气后部上升到850 hPa低涡东北侧的偏东气流形成了冷输送带,从对流层上层沿西北气流下沉到对流层中、下层的干空气构成了干带。强降水与这三条输送带密切相关。

Using conventional observations,hourly surface observations and FY satellite imagery,the features of central-Asian cyclone associated with intense precipitation in Xinjiang from 2014 to 2018 are studied and conceptual models are constructed.Results showed that 24 out of 115 precipitation episodes were due to central-Asian cyclones.Central-Asian cyclones mainly occurred over northern Xinjiang and its surrounding regions,most in the Balkhash Lake and its nearby region,but fewer in the southern Xinjiang.There were 5 cases in June,August and September respectively,but no cases in March,October and December,so we can see the frequency of central-Asia cyclone is higher in summer and early autumn,but lower in spring and winter.These cyclones moved towards east or northeast quickly.They showed up the features of comma clouds or baroclinic leafs on the FY satellite images.The intensities of most central-Asian cyclones ranged from 1000 to 1010 hPa.The locations of cyclones were in the left front quadrant of upper-level jet(ULJ)with 17 cases while 7 cases occurred in the right rear quadrant of ULJ.Although these cyclones were usually weak in intensity,their formation and development were always accompanied by divergence in the upper troposphere.The severe rainfall accompanying the central-Asian cyclones first appeared in warm sector,and then the cyclones interacted with warm fronts or cold fronts,resulting in heavy precipitation.Under the condition of thorgh,vortexes and shear lines in the middle and lower layers,as well as water vapor transport with southerly wind and easterly wind on the east side of the vortexes were favorable for intense precipitation in Xinjiang.The characteristics of the three conveyor belts in the central-Asian cyclones are that the warm and moist air near surface rose up to the upper troposphere,forming the warm conveyor belt,while the cold conveyor belt was formed by the easterly air flows which rose up from the east side of surface cyclone and the rear of easterly cold air to the northeast side of the 850 hPa vortex,and the dry conveyor belt was generated by the dry air subsiding from the upper troposphere down to the middle-low troposphere.The occurrence of intense precipitation was closely related to the three conveyor belts.