2004年主汛期各数值预报模式定量降水预报评估
Evaluation of Quantitative Precipitation Forecasting of Multiple NWP Models in Summer of 2004
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摘要: 随着数值预报技术的飞速发展, 模式定量降水预报已成为天气预报业务工作中的主要参考依据。本文对目前在国家气象中心应用的3个业务运行模式T213L31, HLAFS0.25, 华北中尺度模式MM5和德国模式及日本模式的降水预报产品进行了季节空间分布、区域时间序列演变及统计检验, 试图从空间、时间及统计方面对降水预报产品的预报性能进行综合评估。检验结果表明:目前的数值预报模式对短期时效内定量降水预报均具有一定的空间预报能力, 但强降水中心位置有一定的偏差; 从时间序列演变检验来看, 模式对区域强降水过程的发展趋势具有较强的预报能力, 但降水量预报与实况有一定的差距; 从累加统计评分检验结果来看, 模式短期时效的预报性能差别不大, 全球模式在小中雨预报方面有一定优势, 其中日本模式的综合预报性能最好, 大雨以上量级的预报则是国内的模式有一定的优势, 其中华北中尺度MM5模式, T213L31模式各有所长, 但均存在预报量和预报区偏大问题。Abstract: With the fast development of numerical weather prediction (NWP) technology, the quantitative precipitation forecast of NWP models has become a major basis of everyday operation weather forecast in most countries all over the world at the moment. The precipitation forecasts of five NWP models, including T213L31, HLAFS 0.25, Huabei-meso-MM5, a Germen global model and Japanese global model which are widely applied in National Meteorological Center and other weather prediction offices in China, are verified and assessed synthetically by the spatial distribution of seasonal mean daily rain rate, the time series of regional mean rainfall rate and statistic verification method. The result of the verification shows that there is certain spatial forecast capability for the quantitative precipitation forecasting of short term (for forecast durations of 24/36~48/60 h at 24-hour intervals) by NWP models at present, but there are some biases or errors for position of heavy rainfall center or rain belt. With the forecasting valid time increasing, the errors of rain belt increase. Most models often overestimate the rainfall in the western part of China or underestimate the precipitation in the eastern part of China. Through the verification of the time series of regional mean daily precipitation, it is found that there is more obvious forecasting capability of NWP model for the developing trends of heavy rainfall processes in some regions in the eastern part of China than ordinary processes, and the forecast of the middle and lower reaches of the Yangtze is the best. However, there are some errors for the quantity of forecast precipitation against the observation rainfall. For example, MM5 model often overestimates the rainfall in South China while HLAFS model usually overestimates the precipitation in Southwest China. According to the results of accumulative verification, there are not much differences for Ts of light rain and moderate rain among five models. The global models' Ts are higher than those of regional models, and the forecast by Japanese model is the best among the five models forecast for the two classes. But for heavy rain or more severe rain, the performance of domestic models is super to foreign models. There are unique advantages of MM5 and T213L31 model for different valid time or rainfall classification, but for quantity and area of forecast rainfall are greater than those of observation.
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表 1 用于检验的各种数值预报模式的基本情况
表 2 2004年夏季各数值预报模式全国降水预报累加检验结果
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