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气象:2018,44(1):53-64
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“7·20”华北强暴雨集合预报的中期预报转折和不确定性分析
王毅,马杰,代刊
(国家气象中心,北京 100081)
Ensemble-Based Analysis of Medium-Range Forecast Change and Uncertainty for the 20 July 2016 Severe Heavy Rainfall over North China
WANG Yi,MA Jie,DAI Kan
(National Meteorological Centre, Beijing 100081)
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投稿时间:2017-02-20    修订日期:2017-07-18
中文摘要: 中央气象台主观预报和数值模式对2016年7月20日华北强暴雨过程的中期预报出现了一定的误差,本文利用ECMWF(简称EC)集合预报和T639集合预报等资料对“7·20”华北强暴雨过程的中期预报效果进行了分析,结果发现:(1) EC集合预报在7月16日前后对降雨区及强度的预报出现了明显转折,其因是大尺度影响天气系统的预报发生了转折性变化,7月16日20:00起报的环流形势集合平均场对比15日20:00起报场显示,在河套地区附近500 hPa低槽发展更深,其下游华北高压脊也更强,形成了移动缓慢“东高西低”的环流型,黄河气旋及中低层西南涡北抬加强,导致降雨预报更接近于实况;(2)集合敏感性分析发现对降雨中期预报敏感的区域与转折前后预报的环流差异的分布型一致,引起降雨预报转折的影响系统也是降雨中期预报不确定性的来源;(3) 对于降雨预报最敏感的环流系统是黄河气旋,集合成员预报的黄河气旋偏西偏北,强度越强,则预报的京津冀地区降水量越大。
Abstract:Errors occur for medium range forecast of heavy rainfall over North China on 20 July 2016 by subjective forecast of National Meteorological Centre and numerical models. The medium range forecast performance of this heavy rainfall event is analyzed based on ECMWF ensemble forecast and T639 ensemble forecast data. The results reveal that: (1) there are obvious changes of location and intensity of rainfall of EC ensemble forecast which is caused by change of forecast for large scale weather system before and after 16 July. Compared to forecast initialized at 20:00 15 July, the ensemble mean circulation on 20 July initialized at 20:00 BT 16 July show that trough at 500 hPa over Hetao Region is deeper whereas downstream ridge is stronger, thus forming the pattern of slowly moving “high pressure to the east and low pressure to the west”. The Yellow River cyclone and mid lower level southwest vortex move northward and become stronger. The forecast heavy rainfall is closer to the observed precipitation accordingly. (2) Ensemble sensitivity analysis shows that sensitivity areas are consistent with the spatial pattern of circulation difference before and after the forecast change. The large scale weather systems leading to the change of forecast of heavy rainfall are also sources of uncertainty of medium range rainfall forecast. (3) The most sensitive circulation system to precipitation forecast is the Yellow River cyclone. The Yellow River cyclone, the ensemble member is westward and northward and intensity is deeper, the corresponding forecast precipitation amount over Bejing Tianjin Hebei Region is larger.
文章编号:     中图分类号:P456,P458    文献标志码:
基金项目:国家科技支撑计划项目(2015BAC03B01和2015BAC03B02)及公益性行业(气象)科研专项(GYHY201306002)共同资助
引用文本:
王毅,马杰,代刊,2018.“7·20”华北强暴雨集合预报的中期预报转折和不确定性分析[J].气象,44(1):53-64.
WANG Yi,MA Jie,DAI Kan,2018.Ensemble-Based Analysis of Medium-Range Forecast Change and Uncertainty for the 20 July 2016 Severe Heavy Rainfall over North China[J].Meteor Mon,44(1):53-64.