ECMWF驱动场谱逼近对浙江超强台风“利奇马”（2019）精细化数值预报的影响

为提升高分辨率区域数值天气预报模式性能，基于高质量的ECMWF全球预报模式产品和动力谱逼近方法优势，本文以2019年重创浙江的超强台风“利奇马”为例，探讨了ECMWF驱动场水平风场谱逼近技术对浙江台风精细化预报性能的影响。结果表明:（1）谱逼近对路径预报影响较明显，逐小时路径误差最大修正可达80 km。谱逼近的垂直层次选取对于谱逼近效果有一定影响，总体上800 hPa高度以上谱逼近对台风路径和强度预报改进最佳。（2）谱逼近对浙江台风大风和强降水精细化预报均有大幅改进，对于8级以上大风ETS评分平均改进率为8.0%，最大改进率达20.8%；对最强日降水的暴雨、大暴雨以上降水TS评分改进幅度达11.8%、26.2%。（3）谱逼近对台风路径西偏和浙西南风雨高估的改进主要与对流层形势场及台风引导气流修正、近地层风力减弱、局地山脉地形降水增幅作用减弱有关。

Impact of Spectral Nudging Technique Driven with ECMWF Data on the Fine Numerical Prediction of Super Typhoon Lekima (2019) in Zhejiang Province

In order to improve the performance of high-resolution regional numerical modeling, the impact from spectral nudging (SN) technique driven with the ECMWF data on the fine prediction of super typhoon Lekima (2019) in Zhejiang Province is investigated with the Weather Research and Forecasting (WRF) model, based on both the advantages of high accuracy forecasting data from European Centre for Medium-range Weather Forecasts (ECMWF) and SN technique. The results show that: (1) The improvement by using SN to track Lekima is obvious. For instance, the maximum hourly track error can be reduced by 80 km. Overall the improvement is the most significant for the track and intensity of Lekima (2019) when nudging is adopted above 800 hPa. (2) In Zhejiang Province, the fine predictions of gale and heavy rainfall induced by Lekima (2019) are largely improved through SN technique. Compared to the control experiment, the increased percentage of ETS (Equitable Threat Score) score for the wind stronger than 17.2 m s?1 is about 8% in mean and 20.8% in maximum. At the same time, the increased rates of TS (Threat Score) scores for the rainfall heavier than 50 mm (24 h)?1 and 100 mm (24 h)?1 reach 11.8% and 26.2%, respectively. (3) Further diagnosis illustrates that wind field spectral nudging can amend effectively the west deviation of typhoon track, the over-prediction of strong wind, and the heavy rainfall in southwest of Zhejiang Province, which all are related to the improvements in the atmospheric elements in troposphere, steering flow of Lekima, low-level wind field, and the resulted rainfall enhancement effect by the local topography.