一次北上中亚气旋的结构演变与发生发展机制分析  

Analysis of structure evolution and development mechanism of a Central-Asian cyclone moving northward

作　　者：张昕[1] 熊秋芬[1] 姜晓飞 ZHANG Xin;XIONG Qiufen;JIANG Xiaofei(China Meteorological Administration Training Center,Beijing 100081)

机构地区：[1]中国气象局气象干部培训学院,北京100081

出　　处：《暴雨灾害》2023年第3期303-311,共9页Torrential Rain and Disasters

基　　金：中国气象局短时临近预报教学科研团队项目;中国气象局气象干部培训学院中短期天气预报教学团队项目;中国气象局气象干部培训学院科研项目(青2021-003)。

摘　　要：中亚气旋是造成新疆暴雨、暴雪、大风和沙尘等灾害性天气的一种主要天气系统。为深入了解中亚气旋的结构特征和形成原因,以2017年8月11—12日一次典型北上路径中亚气旋活动过程为例,利用常规气象观测资料、卫星水汽图像与NCEP再分析资料,分析了该中亚气旋的活动特征及环流形势,揭示了其垂直热力和动力结构特征,重点根据准地转理论和位涡守恒原理讨论了其发生发展机制。结果表明:(1)中亚气旋形成于500hPa高空槽前、伴有850hPa低涡和切变线影响以及高空辐散等有利环流背景之下。(2)水汽图像显示中亚气旋从初生、发展到减弱阶段,对应云系经历了由斜压叶状转变为逗点状、再由逗点状演变为螺旋状的过程。(3)地面气旋中心物理量垂直剖面显示,地面气旋初生时,其中心西侧有明显锋区并伴有正相对涡度柱,上升运动仅位于锋区以上;地面气旋发展时,锋区增强且变陡,锋区上下均存在强上升运动,气旋中心上空对流层低层正相对涡度值增大,其西侧对流层高层有正相对涡度高值区东移接近地面气旋中心;气旋减弱时,气旋西侧锋区减弱,其上空垂直上升运动也变弱,低层正相对涡度减小、整层正涡度区变陡。(4)气旋活动过程中,700hPa暖平流明显增强、高低空涡度平流差值增大以及高空辐散增强有利于气旋发生发展;另外,高空干空气的高值位涡区下沉及位涡梯度正值中心东移伴随地面气旋发展。Central-Asian cyclone is one of the major synoptic systems that causes disastrous weather such as heavy rain,snowstorm,strong wind,and sand dust in Xinjiang.In order to deeply explore the structure and the formation of Central-Asian cyclones,taking a Cen-tral-Asian cyclone with typical northward path from August 11 to 12 in 2017 as an example,we analyze its activity characteristics and circu-lation situation,using conventional meteorological observations,FY satellite water vapor images,and NCEP reanalysis data.We reveal its vertical thermodynamic structural characteristics,with the focus on its mechanism of occurrence and development based on the quasi-geo-strophic theory and the potential vorticity conservation.The main results are as follow.(1)The Central-Asian cyclone in front of the high trough at 500 hPa is due to the low vortex and shear line at 850 hPa and the divergence in upper atmosphere.Such condition and background is favorable to the occurrence of Central-Asian cyclone.(2)It can be seen from the water vaper images that the Central-Asian cyclone is in various stages from initial,development,and weakening,and the corresponding cloud systems in the three stages experience a transition from a baroclinic leafy shaped to a comma shaped,and then to a spiral shaped.(3)Vertical cross sections of physical fields in the center of surface cyclone show that there is an obvious cold front and a positive relative vorticity column at the beginning of the cyclone,and the upward mo-tion is only located above the frontal zone.During the development of cyclone,the front intensified and steepened with strong upward motion both above and below.The positive relative vorticity at the lower level above the cyclone center increases,and the high positive relative vor-ticity at the upper level on the west side moves eastward towards the cyclone center.At the weakening stage of the cyclone,the front zone on its west side and the upward motion over and below the cyclone weakens,with the positive relative vorticity at lower level

关 键 词：中亚气旋 准地转理论 位涡 位涡梯度 物理机制 

分 类 号：P443[天文地球—大气科学及气象学]