多家数值产品沿海大暴雨预报性能检验

Performance Verification of Coastal Torrential Rainfall Forecast with Several Numerical Products

2010年8月4—5日和2010年8月21—22日两次天气过程都是在副热带高压外围产生的沿海大暴雨天气,利用多种资料,重点针对基层气象台(站)常用的几家数值模式产品,对两次暴雨过程从环流形势、影响系统、降水量要素等方面进行检验分析。结果表明:各家数值模式产品对暴雨定量预报有一定的预报能力,但降雨量级普遍偏小,对强降水中心的预报稳定性较差;在降水量级上,EC模式预报较准确,具有较高的参考价值。对产生暴雨天气影响系统位置和强度的预报,不同的数值模式有所差异;对西太平洋副热带高压的预报,T639模式和EC模式各时效预报脊点位置跟实况场一致,但强度较实况偏弱;但对高空槽和切变线的预报跟实况都有一定的偏差。因此在暴雨预报中需要在参考数值预报的基础上,结合强对流工具、实况加密资料、物理量场、相似个例和经验外推等其他辅助手段提高暴雨站点预报准确率,从而提升灾害性天气服务的效果。

Two coastal heavy rain events occurred in 4-5 and 21- 22 August 2010 were caused by the subtropical high. For several kinds of numerical products that are used widely, verification is conducted mainly from the aspects of circulation situation, influencing systems, and precipitation elements. The results show that these numerical products have certain prediction capability for heavy rainfall quantitatively, but predicted rainfall levels are generally smaller, and the prediction of the strong precipitation center is poor in stability; the position forecasts of EC and T639 models are more accurate, but the intensity forecasts are smaller than the actual situation. There are certain differences between numerical models and the actual situation in the position and intensity of the weather systems producing the heavy rainfall. As for the West Pacific subtropical high, the 72-h forecast of the T639 model is weaker than the actual storm, and the stability of EC model is higher, but there is certain deviation in upper trough and shear line forecasts. In torrential rain forecasting, it is necessary, on the basis of numerical forecast products, to combine strong convective products with such auxiliary tools as intensive observation data, physical fields, similar examples, experienced empirical extrapolation, etc., to improve the forecast accuracy of heavy rain forecasts.