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气象:2020,46(8):1026-1038
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华南前汛期强降水个例模式降水预报误差成因初探
胡宁,符娇兰,汪会
(国家气象中心,北京 100081; 中国气象科学研究院灾害天气国家重点实验室,北京 100081; 中国气象局-河海大学水文气象研究联合实验室,北京 100081; 中国气象局云雾物理环境重点实验室,北京 100081)
Analysis of the Source of Model Precipitation Prediction Bias for a Heavy Rainfall Event in the Pre-Flood Season in South China
HU Ning,FU Jiaolan,WANG Hui
(National Meteorological Centre, Beijing 100081; State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081; CMA-HHU Joint Laboratory for Hydrometeorological Studies, Beijing 100081; Key Laboratory for Cloud Physics, CMA, Beijing 100081)
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投稿时间:2019-07-16    修订日期:2020-05-27
中文摘要: 2015年5月19—20日,华南出现一次暴雨过程。检验表明欧洲中期天气预报中心全球确定性预报模式(以下简称EC模式)预报的20日强降水落区在广东境内较实况明显偏北,高估了天气尺度系统附近的降水强度,漏报了其南侧暖区内中尺度对流系统(mesoscale convective system, MCS)造成的降水,华东中尺度模式预报明显优于EC模式。利用高分辨率中尺度天气研究预报模式(以下简称WRF模式)对该暴雨过程进行了模拟,对比EC模式降水物理过程,初步探索了EC模式降水预报误差的成因,结果表明:20日位于广东暖区内的对流组织发展成MCS,并造成明显的低层冷池出流和中高层潜热加热,二者共同作用使得中低层气旋式环流在广东中东部发展,配合其南侧的强西南风水汽输送,在气旋式切变附近不断触发新的对流并南移使得广东中南部暖区内出现强降水,WRF模式能较好地模拟出该过程,而EC模式未能预报出暖区对流及其反馈,从而导致其漏报了广东中南部的强降水;EC模式预报的降水与天气尺度环流之间的正反馈进一步加大了降水的预报偏差。EC模式预报的20日白天的强降水主要位于华南北部切变线附近,且以层状云降水为主,降水产生的潜热使得对流层低层切变线附近减压更明显,预报的切变线辐合较分析场明显偏强,使得其预报的切变线附近降水较实况偏强。
Abstract:For the heavy rainfall event in South China in 19-20 May 2015, ECMWF-IFS model (EC mo-del) overestimated its rainfall intensity near the large-scale shear line, but underestimated the heavy rainfall induced by the mesoscale convective systems (MCSs) in warm sector, resulting in a northward displacement bias of the forecasted rainfall compared with the observation in Guangdong Province on 20 May 2015. In this paper, a high resolution numerical simulation of WRF model is performed to explore the source of forecasting error of EC model. The results indicate that the well-organized MCSs in the warm sector induced a significant cold pool outflow, which converged with the strong warm and moist southwest flow. New MCSs were triggered along the convergence line continually and produced heavy rainfall in the warm sector. The WRF model successfully depicts the whole process, while EC model failed to present the above mechanism and caused the underestimated rainfall in the warm sector. The feedback of convective rainfall to synoptic scale flow in South China can be described by WRF model, which can simulate the well-orga-nized MCSs. Most of the rainfall in EC model is the stratiform rainfall caused by the shear line, which may further strengthen the circulation in the middle and low level and increase the precipitation along the shear line in turn. The underestimate of convective rainfall in warm sector and a strong stratiform rainfall feedback work together to cause a northward displacement bias of the forecasted rainfall in EC model.
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基金项目:国家重点研发计划(2018YFC1507703)、国家自然科学基金项目(41975001)、国家重点研发计划(2017YFC1502501)、中国气象局预报员专项(CMAYBY2018-089)、国家科技支撑计划(2015BAC03B02)及灾害天气国家重点实验室开放课题(LASW2014-B05和2018LASW-B02)共同资助
引用文本:
胡宁,符娇兰,汪会,2020.华南前汛期强降水个例模式降水预报误差成因初探[J].气象,46(8):1026-1038.
HU Ning,FU Jiaolan,WANG Hui,2020.Analysis of the Source of Model Precipitation Prediction Bias for a Heavy Rainfall Event in the Pre-Flood Season in South China[J].Meteor Mon,46(8):1026-1038.