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基于快速更新同化数值预报的小时降水量时间滞后集合订正技术
唐文苑, 郑永光
(国家气象中心)
Improvement of Hourly Precipitation Forecast Using a Time-lagged Ensemble based on Rapid Analysis and Forecasting NWP System
Tang Wenyuan, Zheng Yongguang
(National Meteorological Centre)
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投稿时间:2017-12-04    修订日期:2018-09-07
中文摘要: 由中小尺度对流系统造成短时强降水天气的发生发展十分迅速,对其落区和时效的预报预警一直都是预报业务中的难点。本文基于快速更新同化的中尺度数值预报系统GRAPES-RAFS 0.1°×0.1°分辨率逐小时降水预报,首先通过时间滞后(Time-Lagged)集合预报方法构建了多个集合成员,使用平均TS评分值计算相应预报成员权重系数建立预报方程,然后采用频率匹配订正法进行降水量级订正,从而得到集合订正的逐小时降水量预报。2017年8-9月的逐日试验和典型个例预报结果评估表明效果良好。(1)GRAPES-RAFS最新时次的预报场并不完全代表最好的预报效果,通过Time-Lagged集合订正方法自动识别优选预报成员,显著提高了预报能力;(2)GRAPES-RAFS预报存在降水量级偏弱的系统性误差,经过频率匹配方法订正后,在量级预报上更接近实况;(3)时间滞后集合预报对我国中东部(包括黄淮、江淮、江南地区)的小时降水量订正效果最好;(4)进一步使用的频率匹配订正方法显著提升了逐时降水量的预报效果,其在降水频率更高、强度更大的江南南部、华南、西南地区效果更为显著;(5)对于中小尺度的强降水过程,经过上述方法订正后,显著提高了模式对强降水系统位置、形态及降水量级的预报水平。
Abstract:The formation and development of short-term heavy precipitation caused by small and mesoscale convective systems are very rapid, and the prediction and warning of the location and period of precipitation are always difficult in the operational forecast. In this paper, based on hourly precipitation forecast from Rapid Analysis and Forecasting System GRAPES – RAFS ( 0.1 ° x 0.1 °) during August-September 2017, ensemble members are formed by the Time - Lagged ensemble forecast method, using the average TS score to calculate weight coefficients of corresponding ensemble members, and then frequency matching method is adopted to correct precipitation forecast bias. Six conclusions are drawn from this study: (1) for the Rapid Analysis and Forecast System GRAPES-RAFS, the most accurate precipitation forecast does not always come from the most recent ensemble member. Time-Lagged ensemble method can significantly improve the prediction ability of the model by automatic identifying the preferred forecast members; (2) the GRAPES-RAFS hourly precipitation forecast presents significantly systematic weak bias. After correcting by the frequency matching method, the hourly precipitation forecast is more close to the actual situation in the magnitude; (3) the Time-Lagged ensemble method works better for the Middle East China; (4) the frequency matching method works better for South of the Yangtze River, Southern China and southwest China, where precipitation exhibits higher frequency and greater strength; (5) the method can significantly improve the prediction capacity for the precipitation location, amount and the rainfall patterns in the strong precipitation process due to small and medium scale system.
文章编号:201712040526     中图分类号:    文献标志码:
基金项目:国家自然科学基金项目(面上项目,重点项目,重大项目)、气象预报业务关键技术发展专项
引用文本:
唐文苑,郑永光,0.[en_title][J].Meteor Mon,():-.
Tang Wenyuan,Zheng Yongguang,0.Improvement of Hourly Precipitation Forecast Using a Time-lagged Ensemble based on Rapid Analysis and Forecasting NWP System[J].Meteor Mon,():-.