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气象:2019,45(10):1426-1438
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冷池对引发新乡“7·9”特大暴雨的中尺度对流系统的影响分析
徐姝,东高红,熊明明
(天津市气象台,天津 300074; 天津市气候中心,天津 300074)
Impact of Cold Pool on Mesoscale Convective System for Extreme Rainfall over Xinxiang on 9 July 2016
XU Shu,DONG Gaohong,XIONG Mingming
(Tianjin Meteorological Observatory, Tianjin 300074; Tianjin Climate Centre, Tianjin 300074)
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投稿时间:2018-03-26    修订日期:2019-04-09
中文摘要: 利用NCEP再分析资料、常规观测资料、FY-2E卫星TBB资料、多普勒雷达探测资料和地面加密自动站资料分析了2016年7月9日新乡特大暴雨过程的中尺度特征,并揭示了冷池形成原因及其对产生强降水的中尺度对流系统发生发展的影响。研究结果表明:新乡地区特大暴雨是由一个“低质心”结构的后向传播-准静止-涡旋状中尺度对流系统产生的。由层状云和对流性降水产生的冷池出流形成的中尺度温度梯度导致地面辐合进而触发了对流。冷池出流与环境风场形成的假相当位温密集带为对流系统提供不稳定能量,两者强度相当的对峙使能量密集带稳定少动,而中尺度对流系统的上风方即冷池出流南侧由于锋生作用将暖湿空气抬升并不断触发新对流,这种后向传播方式导致中尺度对流系统移动缓慢处于准静止状态,新生对流单体在地面中尺度涡旋流场的作用下呈有组织的涡旋状旋转,不断经过新乡地区造成强降水持续。湿冷的冷池同时也是本次强降水过程近地面水汽来源之一。太行山的阻挡作用导致冷池在山前堆积后向承载层平流方向相反的方向移动;小地形的峡谷效应有助于冷池出流南移,而且为中尺度地面涡旋形成提供了一支重要的西北气流。
Abstract:Based on a variety of NCEP reanalysis data, conventional weather data, temperature of black bold (TBB) data from FY-2E satellite, Doppler radar products and densely observed data from automatic surface weather observation system, the mesoscale characteristics of the torrential rain process that occurred over Xinxiang on 9 July 2016 are analyzed. Furthermore, the formation mechanism of the cold pool is revealed and its impact on mesoscale convective system (MCS) produced extreme rainfall is studied. The results show that: the back-building-quasi-stationary and vortex-shaped MCS, with low-qualify core structure, led to the extreme severe rain over Xinxiang. The cold pool outflow, caused by stratiform precipitation and convective precipitation, led to the surface convergence, and furthermore, the surface convergence triggered and intensified the convection. MCS obtained unstable energy from the dense zone of surface potential pseudo-equivalent temperature formed by cold pool flow and ambient wind. The cold pool outflow and ambient wind were similar in strength, resulting in a stable dense zone of surface potential pseudo-equivalent temperature. For the frontogenetic function, the warm and moist air was lifted to the point of saturation, and upstream reignited deep convection in the south of the cold pool. Such backward propagation decreased the moving speed of MCS, and even made it into a quasistatic state. Under the effect of surface mesoscale vortex system, new convective cells organically rotated like vortex, and repeatedly passed Xinxiang, bringing continuous heavy rain to Xinxiang. The moist cold pool was an important source for the surface water vapor. The Taihang Mountain was thought to trap the cold pool from spreading. As a result, the cold pool moved in the opposite direction of the steering flow. Canyon effect of small topography contributed to the south movement of the cold pool. In addition, it provided an important northwest flow for the surface mesoscale vortex system.
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基金项目:中国气象局预报员专项(CMAYBY2019 006)、天津市气象局重点项目(201812zdxm02)共同资助
引用文本:
徐姝,东高红,熊明明,2019.冷池对引发新乡“7·9”特大暴雨的中尺度对流系统的影响分析[J].气象,45(10):1426-1438.
XU Shu,DONG Gaohong,XIONG Mingming,2019.Impact of Cold Pool on Mesoscale Convective System for Extreme Rainfall over Xinxiang on 9 July 2016[J].Meteor Mon,45(10):1426-1438.