基于T213集合预报的延伸期产品释用方法及初步试验

摘要

基于T213集合预报系统2008年1月中国及附近区域500 hPa高度和850 hPa温度的1～15 d预报资料，构建延伸期产品释用方法，通过对逐日11～15 d预报资料做集合平均和后向衰减权重系数滑动平均，进而得到延伸期（11～15 d）候平均和候距平预报，并对预报效果进行检验，结果表明：对11～15 d预报场做集合平均和后向衰减权重系数滑动平均均能降低预报误差，改善整体预报效果。由此得到的500 hPa高度场和850 hPa温度场11～15 d候平均预报误差与逐日控制预报第5 d的水平相当，候距平相关系数均接近0．6，整体而言效果较好，具备一定的应用价值。500 hPa 高度场和850 hPa 温度场11～15 d候距平预报在中国大陆地区位相准确率均较高，东南沿海和东北部分地区稍差，且850 hPa 温度场的位相准确率整体高于500 hPa高度场。候距平预报对延伸期（11～15 d）的大范围持续性异常距平具有较强的捕捉能力，对异常距平出现的范围和分布、强距平中心的位置的预报均较好，但强度整体偏弱。%Based on the 11-15 d forecast data of T213 EPS 500 hPa geopotential height and 850 hPa tem-perature in China and the adjacent regions in January 2008,an interpretation method of extended range forecast product is designed,and the pentad average and pentad anomaly forecast of extended range (1 1-1 5 d)are got after the 1 1-1 5 d daily forecast data are processed by ensemble mean,moving average of backward decaying weighting coefficient and pentad average.Meanwhile,the forecast effect of the pentad average and pentad anomaly forecast is verified.The results show that ensemble mean and moving average of backward decaying weighting coefficient both can reduce the prediction error and improve the forecast effect.The pentad mean absolute error of the 11-15 d pentad average forecast of 500 hPa geopotential height and 850 hPa temperature are equal to the level of the 5th d forecast of daily control forecast.The pentad anomaly correlation coefficients of 500 hPa geopotential height and 850 hPa temperature are both close to 0.6.Taken as a whole,the forecast effect of 11-15 d pentad average is good enough to use.The phase accuracy rate of 11-15 d pentad anomaly forecast of 500 hPa geopotential height and 850 hPa tem-perature are both very good in mainland China except for part of the southeast coastal area and the north-east area.In general,the phase accuracy rate of 850 hPa temperature is better than 500 hPa geopotential height.The 11-15 d pentad anomaly forecast can reflect the persistent large-scale anomalous anomaly. The range,distribution and center of anomalous anomaly can all be forecasted well but the overall intensity is weaker than observed field.