登陆台风外围极端降水过程的中α尺度系统特征  

Alpha mesoscale characteristics of extreme precipitation processes outside landfall typhoons

作　　者：李君 胡晓琳 丛春华 LI Jun;HU Xiaolin;CONG Chunhua(Key laboratory for Meteorological Disaster Prevention and Mitigation of Shandong,Ji'nan 250031,China;Zibo Meteorological Bureau of Shandong Province,Zibo 255000,China;Shandong Meteorological Observatory,Ji'nan 250031,China)

机构地区：[1]山东省气象防灾减灾重点实验室,山东济南250031 [2]山东省淄博市气象局,山东淄博255000 [3]山东省气象台,山东济南250031

出　　处：《海洋预报》2023年第6期102-114,共13页Marine Forecasts

基　　金：中国气象局创新发展专项(CXFZ2023J015);华东区域气象科技协同创新基金合作项目(QYHZ201812);山东省气象局引导类科研项目(2021SDYD40)。

摘　　要：采用全国多普勒雷达反射率因子拼图、山东省自动气象观测站数据,结合ERA50.25°×0.25°再分析资料,分析台风“利奇马”造成山东极端暴雨的中α尺度系统特征。结果表明:台风北侧东南急流与西风槽后偏西气流的切变引发的中α尺度辐合区是直接造成极端降水的中尺度系统;对流始于800~750 hPa,随后沿西风槽向高层发展,再伸展到低层,在台风北侧低层切变附近强烈发展;初始对流由低空急流触发,后高空出流迅速增强,促进上升运动发展,高低空急流上下耦合的正反馈作用促进了中α尺度辐合区深度发展,是极端降水发生发展的重要原因;初始对流发生在对流不稳定环境中,凝结潜热释放造成的湿斜压性和中低层垂直切变形成的条件性对称不稳定增长,使对流发展为有组织而长时间维持的深对流;水平风场将水汽汇集向暴雨区,上升运动将水汽向中高层输送,湿层逐渐增厚,当水汽通量15 g/(cm·hPa·s)等值线向上伸展到500 hPa时,降水强度超过20 mm/h;鲁中山区地形是影响降水中心落区的重要因素。This paper uses puzzles of the national Doppler radar reflectivity,data from regional automatic weather observation station,combined with NCEP/NCAR 6-hour daily re-analysis data,to analyze the mesoscale convective system that caused extreme rainstorms in Shandong by Typhoon"Lekima"and found:The mesoscale convergence system caused by the shear of the southeast jet on the north side of the typhoon and the westward airflow after the westerly trough is the mesoscale system that directly causes extreme precipitation.Convection starts from 800~750 hPa and then develops along the westerly trough to the upper layers,Extending to the lower level,it develops strongly near the low-level shear on the north side of the typhoon.The initial convection was triggered by the low-level jet stream,and the outflow increased rapidly after the upper level,promoting the development of upward motion.The coupling positive feedback effect of the upper and lower air jet stream promoted the depth development of the middleαscale convergence zone,which is an important reason for the development of the extreme precipitation.During the development of the mesoscale system,there is an obvious high-level dry and cold air intrusion from the northwest,and the upper layer is ahead of the lower,which is conducive to the enhancement of instability and promotes the formation and development of mesoscale system,which in turn increases precipitation.When the height of dry and cold air invades into 500 hPa,initial convection appears.The lower intrusion height,the more precipitation,and the most precipitation appears in the boundary layer.The horizontal circulation concentrates the water vapor to the heavy rain area.The vertical upward movement of the mesoscale convergence system transports the water vapor to the middle and upper layers,and the wet layer gradually thickens.When the contour of the water vapor flux 15 g/(cm·hPa·s)extends upward to 500 hPa,the precipitation intensity increases to more than 20 mm/h.The terrain of central Shandong mountain is

关 键 词：台风“利奇马” 中α尺度系统 高低空急流 条件性对称不稳定 水汽 地形 

分 类 号：P445[天文地球—大气科学及气象学]