中低层增温对强降水中涡旋形成的敏感性研究  

Sensitivity Study of Middle-low Level Temperature Increase for Mesovortex Formation in a Heavy Rainfall Case

作　　者：陈贵川 吴钲 谌芸 李强 朱岩 

机构地区：[1]重庆市气象台,重庆401147 [2]重庆市气象科学研究所,重庆401147 [3]国家气象中心,北京100081

出　　处：《高原气象》2016年第6期1498-1511,共14页Plateau Meteorology

基　　金：公益性行业(气象)科研专项(GYHY201406001);中国气象局气象关键技术集成与应用项目(CMAGJ2015M49);中国气象局预报员专项(CMAYBY2013-055)

摘　　要：2012年7月21日22:00-23:00重庆盘龙出现了180.9 mm·h-1的极端强降水,这在西南低涡暴雨中比较罕见的。通过对雷达资料的分析,发现此次极端强降水过程中有近于中气旋强度的中涡旋形成和发展。为了研究中低层增温对强降水中涡旋形成的作用,利用中尺度数值模式WRF-ARW,结合雷达资料同化的ARPS-3DVAR方法和复杂云分析方案,并对中低层进行中心增温同化敏感性实验,对上述过程中出现的近于中气旋强度的强降水中涡旋进行了数值模拟。结果表明:全球预报系统GFS(Global Forecasting System)预报场同化雷达反射率因子和径向风资料之后,能较好地模拟出西南低涡东侧准线性对流系统(Qusi-Linear Convective System,QLCSs)、强降水落区、强降水中心、盘龙附近的β中尺度气旋式环流以及镶嵌在其中的γ中尺度涡旋(即中涡旋);850 h Pa和700 h Pa经过中心增温同化后能增强中涡旋的强度,当700 h Pa中心增温2℃同化后能模拟出与盘龙附近相似的近于中气旋强度的中涡旋。同时,此次强降水中涡旋形成的机制为中低层异常高的温湿条件导致异常强的对流不稳定性,上升运动快速发展,中低层水汽通量辐合迅速增强,大量水汽凝结并急剧释放潜热,高温高湿气柱随上升运动迅速增长导致增温中心附近位势高度急剧下降,水平位势梯度加大,风速增大,中涡旋迅速发展增强到中气旋的强度。表明中低层垂直风切变偏弱的环境中中低层异常高的温湿条件是形成强上升运动,促进近于中气旋强度的中涡旋形成的重要条件。An extreme precipitation event characterized by hourly rainfall of 180. 9 mm ·h-1occurred near Panlong,Chongqing from 22： 00 to 23： 00 on July 21 2012,which was fairly rare among rainstorms caused by the southwest vortex. An analysis of Radar data reveals that during the process,a mesovortex that almost rivals a mesocyclone was observed to had been forming and evolving. To investigate the impact of low-level warming exerted on the formation of mesovortex,basing on WRF model,a set of numerical simulations that combined complex cloud analysis and ARPS-3DVAR method that incorporated radar assimilation,together with the sensitivity experiment of center temperature increment assimilation（ CTIA） on low-level atmosphere,had been carried out to explore the relationship between mesovortex and aforementioned extreme precipitation. The results indicate that after the assimilation of reflectivity and radial velocity of radar,the GFS forecast performs well on the simulation of the qusi-linear convective system（ QLCSs）,the area and the center of heavy rainfall and the meso-β-scale cyclonic circulation in the eastern part of Southwest vortex near Panlong with a meso-γ-scale vortex embedded in.The intensity of meso-γ-scale vortex was increased due to CTIA done at both level of 850 h Pa and 700 h Pa. With2 Celsius degree’s incensement of CTIA at 700 h Pa,the mesovortex which was comparable to a mesocyclone was successfully simulated. Meanwhile,the mechanism of the forming of mesovortex could be explained as follows： the abnormal warmness and humidity at lowlevel lead to the abnormal intensification of convective instability,which further triggered the booming development of updraft. As vapor flux converges drastically,a large amount of vapor condenses,rapidly releasing latent heat. The geopotential height near the warming center dropped rapidly as warm and humid air column stretches due to the intensification of updraft. The horizontal gradient of geopotential height thus increase as well as the wind speed sur

关 键 词：数值模拟 中心增温同化 西南低涡 中涡旋 中气旋 

分 类 号：P435.1[天文地球—大气科学及气象学]