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气象:2018,44(1):142-150
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冷空气和热带低压共同作用下的一次暴雨预报失败原因分析
陈淑琴1,徐燚2,曹宗元1,刘菡1,陈梅汀1
(1 浙江省舟山市气象台,舟山 316021 2 浙江省气象台,杭州 310017)
Results of a Failure Forecast About a Rainstorm Caused by Cold Air and Tropical Low Pressure
CHEN Shuqin1,XU Yi2,CAO Zongyuan1,LIU Han1,CHEN Meiting1
(1 Zhoushan Meteorological Observatory of Zhejiang Province, Zhoushan 316021 2 Zhejiang Meteorological Observatory, Hangzhou 310017)
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投稿时间:2017-02-28    修订日期:2017-07-17
中文摘要: 利用NCEP再分析资料、高空、地面观测资料和雷达资料分三个阶段,从水平、垂直方向分析了2014年8月18—20日冷空气和热带低压共同作用下的浙江暴雨过程中水汽输送、垂直运动过程,以及对流不稳定特征,总结预报失败原因。结果表明:(1)第一阶段浙北的暴雨主要是由冷锋引起的,但南海热带低压的存在加强了西南暖湿气流,使得北方冷空气与西南暖湿气流相遇,产生变形场锋生作用。预报偏小的原因主要是没有注意到热带低压的存在和影响,其次是对降水时间的长度也估计不足。(2)第二阶段浙中南的大暴雨,水汽主要是由热带低压东侧和南侧的偏南或西南气流输送的。热带低压在福建登陆后,与冷空气相遇,移动缓慢,导致低层在浙南有中尺度辐合线长时间维持。两个系统耦合,产生了强烈的上升运动,低层又有不稳定能量释放,最终产生了大暴雨。预报偏小的原因是对热带低压的作用估计不足(包括水汽、动力和不稳定能量方面)。(3)第三阶段预报偏大的原因主要是数值预报误差较大。得出的一些启示: 预报暴雨时要注意分析降水时间长度,也应重视分析热力条件,以及对数值预报的订正应用。热带系统和中纬度系统相遇,往往会造成大暴雨,主要原因是两个系统耦合会造成强烈的上升运动,同时两个系统对峙会使强降水区长时间维持在同一个地方,热带系统附带的急流又提供了充足的水汽、能量,所以实际雨量往往会比数值预报更大。
Abstract:Based on the NECP/NCAR reanalysis data, high level and surface observation data and radar data, this paper analyzes the three stages of the heavy rainfall that occurred in Zhejing Province during 18-20 August 2014. The water vapor transmission, vertical movement and convective instability of the rainstorm are investigated from horizontal and vertical directions, so the lesson of a failure forecast could be summarized. The results are as follows. (1) The first stage of the heavy rainfall in northern Zhejiang was mainly caused by the cold front, but the existence of the tropical depression played a positive role in strengthening warm wet flow coming from southwest, making the north cold air meet with the warm wet flow, which induced the frontogenetic function in the deformation field. So, the neglected existence and influence of the tropical depression are the main inaccurate reason of the less precipitation forecast. In addition, the duration of the rainstorm was also underestimated. (2) The second stage of the heavy rainfall happened in the central and southern Zhejiang. The southerly and southwesterly flow around the eastern or southern side of the low pressure drew abundant water vapor. There was a slow moving cold front that resulted in the maintenance of the mesoscale convergence line in the lower atmosphere for a long time when the tropical depression landed at Fujian Province. There existed the coupling of the two systems, generating strong upward motion, and the instability energy in the lower level released. Finally, the severe downpour occurred. So, the underestimated influences of the tropical depression (moisture, dynamic and instability energy conditions) are the main inaccurate reason for the less precipitation forecast. (3) The big error of numerical forecasting is a crucial reason for overestimating the precipitation in the third stage. As a result, we find that the duration of the rainfall, heat condition and correction of numerical forecasting played important roles in predicting the precipitation of such rainstorm. Besides, there was strong upward motion caused by the coupling of tropical weather system and mid latitude weather system, and meanwhile, severe precipitation area maintained at the same place when the two systems confronted each other. What is more, plenty of water vapor and energy brought by jet caused the heavy rainfall frequently. Therefore, the actual rainfall was bigger than the forecasted rainfall.
文章编号:     中图分类号:P456,P458    文献标志码:
基金项目:国家自然科学基金青年科学基金项目(41705031)和中国气象局预报员专项(CMAYBY2017 029)共同资助
引用文本:
陈淑琴,徐燚,曹宗元,刘菡,陈梅汀,2018.冷空气和热带低压共同作用下的一次暴雨预报失败原因分析[J].气象,44(1):142-150.
CHEN Shuqin,XU Yi,CAO Zongyuan,LIU Han,CHEN Meiting,2018.Results of a Failure Forecast About a Rainstorm Caused by Cold Air and Tropical Low Pressure[J].Meteor Mon,44(1):142-150.