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气象:2018,44(11):1414-1423
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四川盆地一次极端大风天气过程成因及预报着眼点分析
康岚,刘炜桦,肖递祥,师锐,王秀明
(四川省气象台,成都 610071; 高原与盆地暴雨旱涝灾害四川省重点实验室,成都 610071; 中国气象局气象干部培训学院,北京 100081)
Analysis on Formation Reason and Forecast of an Extreme Gale in Sichuan Basin
KANG Lan,LIU Weihua,XIAO Dixiang,SHI Rui,WANG Xiumin
(Sichuan Meteorological Observatory, Chengdu 610071; Heavy Rain and Drought Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province, Chengdu 610071; China Meteorological Administration Training Centre, Beijing 100081)
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投稿时间:2017-04-05    修订日期:2018-08-23
中文摘要: 利用常规观测资料、FY-2E卫星云图、多普勒雷达产品、闪电定位资料、自动气象站资料等,分析了2015年4月4日傍晚到夜间发生在四川盆地的极端大风天气过程。分析指出:本次雷暴大风过程是由冷锋对暖湿气团的强迫抬升及干冷空气进入暖湿区域触发形成。中空干层、大的温度直减率、高低空急流耦合区、低层温度脊附近是利于极端雷暴大风出现的潜势区域。该区域为雷暴形成提供了条件不稳定、水汽、动力抬升等有利环境条件。冷空气首先从盆地西北部中低层入侵,在低层切变线上触发生成了一系列雷暴单体,在最有利于对流发展的潜势区域迅速发展。潜势区域中线状回波北段的中尺度涡旋环流、前侧入流和后侧入流的相互作用形成单体弓形回波,该弓形回波具有比普通雷暴更高的反射率因子、垂直液态含水量。根据雷达回波演变特征推断,本次极端大风是由单体弓形回波带来的湿下击暴流所导致。弓形回波中高反射率因子的高度连续下降意味着下沉气流伴随降水粒子下降,干空气被夹卷进入下沉气流使得雨滴被迅速蒸发,大大加强了下沉气流强度,因而显著增加了大风强度。分析还指出:通过分析对流发展背景条件,确定最有利对流发展的潜势区域,关注该区域中回波的生成、形态特点、演变特征,可提前预警大风天气。
Abstract:Using conventional weather data, FY-2E satellite data, Doppler radar products, lightning location data, automatic weather station data, this paper analyzes the 4 April 2015 evening to night thunderstorm gale process in Sichuan Basin. Our analysis shows that the thunderstorm gale process was formed by the cold front forced uplift on warm air mass as well as dry and cold air into the warm area. The area of hollow dry layer, large temperature lapse rate, coupling of high low jet area and the low level temperature near the ridge were conducive to the potential area of extreme thunderstorm gale. This area provided a favorable environmental condition for the thunderstorm such as significant unstable conditions, water vapor, dynamic uplift, etc. Cold air firstly invaded from the middle and lower layers of the northwestern part of the basin and triggered a series of thunderstorm cells on the low level shear line, which developed rapidly in the most favorable area for the development of convection. The interaction of the mesoscale vortex, the front inflow and the posterior inflow into the northern part of the latent region led to the formation of a single bow echo, which had much higher reflectivity and liquid water content than ordinary thunderstorm. According to the development characteristics of radar echo, the extreme gale was caused by the wet downburst brought by single bow ech. The descending height of the high reflectivity factor in the bow echo means that the sinking air stream was accompanied by a drop in precipitation particles. The dry air was trapped in the sinking air stream and raindrops evaporated quickly, greatly increasing the intensity of the sinking air stream, and thus increasing the strength of the gale. Our analysis also indicates that, by analyzing the background conditions of convective development, forecasters could identify the potential regions for the most favorable convective development paying close attention to the location of the trigger conditions and the characteristics of the radar echo shape as well as the evolution characteristics in the region could be helpful for the early warning of gale weather.
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基金项目:公益性行业(气象)科研专项(GYHY201506006)和四川强对流预报创新团队(川气函〔2017〕313号)、全国强对流预报专家团队共同资助
引用文本:
康岚,刘炜桦,肖递祥,师锐,王秀明,2018.四川盆地一次极端大风天气过程成因及预报着眼点分析[J].气象,44(11):1414-1423.
KANG Lan,LIU Weihua,XIAO Dixiang,SHI Rui,WANG Xiumin,2018.Analysis on Formation Reason and Forecast of an Extreme Gale in Sichuan Basin[J].Meteor Mon,44(11):1414-1423.