1998年7月河套气旋强烈发展时的暴雨过程分析  

Diagnosis of a Heavy Rain Event Caused by the Intense Development of Yellow River Cyclone in July,1998

作　　者：梁丰[1] 陶诗言[1] 

机构地区：[1]中国科学院大气物理研究所

出　　处：《应用气象学报》2007年第5期577-585,共9页Journal of Applied Meteorological Science

基　　金：国家自然科学基金课题"干旱背景下黄河流域致洪暴雨的多尺度天气学模型研究"(ZR2006-03);北京市科委项目"北京奥运会国际天气预报示范计划支持技术研究"(Z0006279040191)共同资助

摘　　要：采用位涡理论对1998年7月4—7日的一次河套气旋强烈发展中的暴雨过程进行分析。结果表明:此次夏季河套气旋的强烈发展是在高层正位涡平流和低层暖平流的共同作用下产生的。高空双急流结构产生的强烈辐散加强了低层辐合,有利于气旋的加强。强降水出现在河套气旋强烈发展过程中,是由高层冷空气与季风涌带来的西南暖湿气流辐合而引起的大尺度降水过程。在这次气旋强烈发展过程中,对流层低层到中上层均出现强的上升气流,使得南方深厚的暖湿空气不断随西南风流入暴雨区上空。暴雨发生时,华北地区处于地面Ω型的θse高能舌之中,其上空500 hPa存在一个由大尺度动力强迫形成的东北—西南向的非地转湿Q矢量辐合带,对流云带与Q矢量辐合中心有非常好的对应关系。A Yellow River cyclone intensifies rapidly during July 5 to 7, 1998. Its center pressure decreases by 12 hPa over a 24 h period and it produces heavy rain with the maximum rainfall exceeding 350 mm in Beijing. A diagnostic study is conducted from a potential vorticity or ＂PV thinking＂ perspective using NCAR/NCEP 6 hourly reanalysis data. The results show that the rapid development of the Yellow River Cyclone is related to the coupling between a surface low system and an upper level positive PV anomaly. When the positive PV anomaly near the tropopause advects over a pre-existing surface cyclone, the cyclone deepens dramatically. Warm advection at 850 hPa intensifies the development of cyclone. Heavy rain occurs in the rapid intensification stage of the Yellow River Cyclone. This is a synoptic scale precipitation case, which is caused by the convergence between cold air descending from stratosphere and southwest warm and moisture air flow brought by the Monsoon Surge. On the vertical cross section through the region of heavy rain, abrupt jump of tropopause is shown clearly. The tropopause is near 250 hPa on the cold side and rises dramatically to above 100 hPa on the warm side. The extent of the descent of stratospheric air in the storm can be deduced by the tongue of 1 PVU extending from 200 to 600 hPa. While the cyclone intensifies rapidly, there are strong ascending motions, which lead to the deep moisture air from the south of China transporting to the heavy rain region continually by southwest wind. From the low to mid level of troposphere, the humidity increases. The amount of precipitable water vapor increases 10.2 mm in 24 hours. The atmosphere is baroclinic over heavy rain region. High level jet with wind speed greater than 30 m·s^-1 and low level jet with wind speed greater than 12 m·s^-1 are found at 200 hPa and 850 hPa, respectively. At surface, a tongue of high θse value prevails in North China. At 500 hPa, there is a convergent zone of non-geostrophic wet Q vector extending from southwest to n

关 键 词：河套气旋 位涡 非地转湿Q矢量 暴雨 

分 类 号：P447[天文地球—大气科学及气象学] P458.121.1