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气象:2018,44(4):485-499
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2017年广州“5·7”暖区特大暴雨的中尺度系统和可预报性
伍志方1,2,蔡景就1,林良勋1,胡胜1,张华龙1,韦凯华1
(1 广东省气象台,广州 510641 2 中国气象局广州热带海洋气象研究所/广东省区域数值天气预报重点实验室,广州 510641)
Analysis of Mesoscale Systems and Predictability of the Torrential Rain Process in Guangzhou on 7 May 2017
WU Zhifang1,2,CAI Jingjiu1,LIN Liangxun1,HU Sheng1,ZHANG Hualong1,WEI Kaihua1
(1 Guangdong Meteorological Observatory, Guangzhou 510641 2 Institute of Tropical and Marine Meteorology/Guangdong Provincial Key Laboratory of  Regional Numerical Weather Prediction, CMA, Guangzhou 510641)
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投稿时间:2017-08-06    修订日期:2018-03-06
中文摘要: 2017年5月7日广州发生了特大暴雨,各家确定性业务预报模式均漏报了此次过程。本文利用常规观测资料和广州天气雷达资料对此次暖区特大暴雨过程的天气尺度背景、中尺度系统演变和可预报性进行了详细分析,同时通过分析ECMWF集合预报中成功预报出广州周边地区出现局地强降水与预报了弱降水的成员间的差异,探讨影响本次大暴雨发生的关键触发因子。结果表明:2017年“5·7”大暴雨的环境条件和动力强迫较弱,在弱风场环境下,冷高压后部东南风或偏南风回流,经过城市热岛区域,转为偏暖气流,与山坡下滑冷气流在山前一带形成的水平风场辐合,结合山前强水平温度梯度,共同触发了初生对流单体。其后,雷暴出流和边界层暖湿气流形成的辐合线又触发新生单体,并使已减弱的降水单体重新加强产生第二阶段强降水。前两个阶段的局地特大暴雨分别是由稳定少动的块状强回波单体发展到嵌有中涡旋的强单体和较长生命史的弱HP型超级单体造成的,第三阶段的大暴雨是由向南传播合并新生单体并随短波槽东移的带状回波造成;三个阶段成熟回波垂直结构上均呈低质心暖云降水的特点。由ECMWF集合预报成功预报出局地强降水与弱降水成员之间的差异可见,加强的温度梯度及地面风场辐合可能是本次局地强降水的重要触发因子。短期时效内数值模式难以做出暖区尤其是弱风场环境下暴雨以上降水预报,目前的监测和短时临近预警是主要手段。
Abstract:Based on the conventional observation data and the Guangzhou Doppler weather radar data, this article analyzed the synoptic background, mesoscale systems and predictability of the torrential rain process which occurred in Guangzhou on 7 May 2017. By contrasting the members of ECMWF ensemble forecast which successfully forecasted the local heavy precipitation on 7 May 2017 with the failed member, key triggering factor affected this process was investigated. The results show that the ambient condition and dynamic forcing were weaker on 7 May 2017. In the context of weak wind field, a convergence line formed between the warm flow from the sea and the cold downslope wind in the front of mountain, combined with the intense temperature gradient, initially triggering the generation of convective storms. Subsequently, the outflow of the preexisting thunderstorms impacted the warm, moist flow at boundary layer, inducing new convergence lines continually. Therefore the weakened storm-cells enhanced again and aroused the second stage of heavy rainfall. The first stages of the local torrential rain on 7 May 2017 was induced by short-lived severe local storm with a meso-vortex evolved from the steady and strong block-shaped echo. The second stage of this torrential rain was caused by long-lived heavy precipitation (HP-type) supercell storm. However, the band echo merging from a mass of new-born convective cells and moving eastward with the short-wave trough was responsible for the third stage of this torrential rain. The radar echo had the low-quality core vertical structure and warm cloud precipitation character during all the three stages. It has turned out that more enhanced temperature gradient and surface wind convergence might be the important triggering factors for local severe precipitation. This finding is based on the member comparison of ECMWF ensemble forecast that successfully forecasted the local heavy and weak precipitation on 7 May 2017. Now, it is still difficult for numerical models to forecast the extremely heavy rains in short lead-time forecast under the condition of warm sector and, especially, the weak wind field. The main method for this is to enhance rainstorm disaster monitoring and early warning.
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基金项目:公益性行业(气象)科研专项(GYHY201506006)、气象预报业务关键技术发展专项[YBGJXM(2017)02-05]、国家科技支撑计划(2015BAK11B01)、广东省科技计划项目(2015A020217008)、中国气象局强对流预报技术专家创新团队和广东省短临监测预警技术创新团队共同资助
引用文本:
伍志方,蔡景就,林良勋,胡胜,张华龙,韦凯华,2018.2017年广州“5·7”暖区特大暴雨的中尺度系统和可预报性[J].气象,44(4):485-499.
WU Zhifang,CAI Jingjiu,LIN Liangxun,HU Sheng,ZHANG Hualong,WEI Kaihua,2018.Analysis of Mesoscale Systems and Predictability of the Torrential Rain Process in Guangzhou on 7 May 2017[J].Meteor Mon,44(4):485-499.