“6·30”川渝特大暴雨过程中西南低涡发展机制模拟分析  

A Numerical Simulation Study of the Southwest Vortex Mechanism during the "6·30" Heavy Rain Event in Sichuan and Chongqing

作　　者：邓承之 赵宇[2] 孔凡铀 翟丹华 李强 何跃 DENG Chengzhi;ZHAO Yu;KONG Fanyou;ZHAI Danhua;LI Qiang;HE Yue(Chongqing Meteorological Bureau,Chongqing 401147,China;Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)/Key Laboratory,Meteorological Disaster of Ministry of Education(KLME),NUIST,Nanjing 210044,Jiangsu,China;Center for Analysis and Prediction of Storms,University of Oklahoma,Norman 73072,USA)

机构地区：[1]重庆市气象台,重庆401147 [2]南京信息工程大学气象灾害预报预警与评估协同创新中心/气象灾害教育部重点实验室,江苏南京210044 [3]俄克拉荷马大学风暴分析与预报中心,美国诺曼73072

出　　处：《高原气象》2021年第1期85-97,共13页Plateau Meteorology

基　　金：国家重点研发计划项目(2017YFC1502000);重庆市基础研究与前沿探索项目(cstc2018jcyjAX0434);重庆市风暴尺度集合数值预报系统建设项目。

摘　　要：利用地面加密自动站、NCEP(1°×1°)再分析及WRF-ARW数值模拟资料,对造成2013年6月29日至7月1日川渝地区特大暴雨过程的西南低涡的演变特征及热动力机制进行了诊断分析。此次特大暴雨过程分为三个阶段,其中与西南低涡发展相关的第二阶段为主要降雨时段。结果表明:(1)西南低涡生成后,呈现增强-减弱-再次增强的波动性演变特征,在6月30日上午和夜间分别经历了两次显著的涡度发展过程,并在第二次发展过程中达到最强。(2)低空辐合是西南低涡最主要的涡源,由低空辐合导致的正涡度增加近乎贯穿于整个西南低涡的生命史。在西南低涡的第二次发展过程中,中层辐合和涡度的垂直输送显著增强,也是西南低涡的重要涡源。(3)负值非平衡动力强迫激发了低空辐合的增长,在非平衡动力强迫的各项中,位势高度的拉普拉斯项为非平衡动力强迫提供了主要的负贡献来源。(4)非绝热加热先于西南低涡而增强,两者间的正反馈作用可能是西南低涡波动性发展的重要机制。在关闭了微物理过程中的潜热和地面潜热及感热通量的敏感性试验中,西南低涡及降雨的模拟均有不同程度的减弱。The Southwest Vortex weather event that brought extremely heavy rainfall in regions across Sichuan and Chongqing from 29 June to 2 July 2013 was analyzed using datasets from intensive automatic weather stations,NCEP reanalysis(1° ×1°)and WRF-ARW numerical simulations. This extremely heavy rainfall episode could be classified into three stages,with the primary precipitation process occurred in the second stage that was closely associated with the Southwest Vortex development. The analyses revealed that:(1)The Southwest Vortex in this case,after emerged,exhibited enhance-weaken-enhance pattern,with vorticity intensification during morning and midnight on 30 June,respectively,peaked in the second period.(2)Low-level convergence was the primary origin of positive vorticity throughout the Southwest Vortex life cycle. Mid-level convergence and vertical transport of vorticity increased significantly during the second intensification period of the Southwest Vortex.(3)The low-level convergence was maintained by negative non-equilibrium dynamic forcing,mainly attributed to Laplace term of potential height.(4)Diabatic heating intensified ahead of Southwest Vortex’s intensification. The positive feedback between the two might be a key mechanism for the development of the Southwest Vortex. Sensitivity experiments using WRF model simulations with latent heating from microphysics and sensible and latent heat fluxes from the surface turned off produced weaker Southwest Vortex and precipitation.

关 键 词：暴雨 西南低涡 涡度收支 非平衡动力强迫 非绝热加热 

分 类 号：P458[天文地球—大气科学及气象学]