远距离台风影响陕北突发性暴雨成因分析  

ANALYSIS OF THE ABRUPT RAINSTORM IN NORTH SHAANXI IN RELATION TO TYPHOON FAR AWAY

作　　者：井喜 贺文彬 毕旭 艾丽华 

机构地区：[1]陕西省榆林市气象局,榆林719000

出　　处：《应用气象学报》2005年第5期655-662,共8页Journal of Applied Meteorological Science

摘　　要：该文对2002年7月4～5日发生在陕西子长县受远距离台风影响而产生的突发性暴雨进行了诊断分析.结果表明:子长特大暴雨是由于β-中尺度强对流云团在子长重复出现而产生的.中低纬度系统的相互作用形成了有利于中尺度强对流云团在子长生成、发展和重复出现的水汽条件、不稳定条件、动力条件和天气尺度环流背景.湿位涡诊断分析表明:当台风向西北方向行进时,(1)暴雨区对流层低层MPV1负值发展的同时伴随对流高层MPV1正值的发展,为对流层低层不稳定能量的充分积累创造了条件;(2)暴雨区形成有利于中尺度强对流云团生成发展的湿位涡正压项、斜压项垂直结构配置;(3)850 hPa等压面上MPV2等值线密集区和MPV1=-2 PVU中尺度强对流不稳定核心区形成耦合,耦合区对下游中尺度强对流云团发生发展指示意义明显.当台风向北偏东方向行进时,暴雨区对流层低层和高层形成双层不稳定;850 hPa MPV2等值线密集区东移,暴雨区MPV2正值发展,积累的对流不稳定能量在子长形成集中猛烈释放.Diagnosis is performed of the abrupt rainstorm on 4--5 July, 2002 in Zichang County of north Shaanxi Province under the influence of a far-away typhoon. Results suggest that the rainfall event happens due to the repeated occurrence of a meso-β intensely convective cluster moving over the study county. Obviously, the interactions between weather systems at low and middle latitudes are responsible for the moisture, instability, dynamic condition and a synoptic circulation background that favor the genesis, development and repetitive occurrence of the meso convective cloud cluster over the study county. Diagnostic study of moist potential vorticity （MPV） indicates that the typhoon traveling toward the northwest leads to the fact that 1） the low-level negative MPV1 intensification is accompanied by the positive MPV1 enhancement in the higher troposphere, thereby creating a condition for the accumulation of unstable energy in large amounts at lower levels; 2） the rainstorm area gives rise to the favorable distribution of MPV barotropic and baroclinic terms in vertical answerable for the generation and development of the cloud cluster; 3） the area of close-together MPV2 contours at the 850 hPa level is coupled with the MPV1 = - 2 PVU meso convectively unsteady core, which is clearly indicative of the production and evolution of the cluster downstream of the coupling. Diagnosis also shows that when the typhoon moves north by east the instability occurs at lower and high levels over the rain zone; the area of MPV2 close-together contours at 850 hPa moves eastward and positive MPV2 is intensified, resulting in dramatic release of accumulated convectively unsteady energy in the study county.

关 键 词：西北涡 台风 湿位涡 突发性暴雨 成因分析 距离 对流不稳定能量 强对流云团 陕北 诊断分析 

分 类 号：P458.121.1[天文地球—大气科学及气象学] P444