Zhejiang Institute of Meteorological Sciences
To improve the performance of high-resolution regional numerical model, based on both advantages of high accuracy forecasting data from European Centre for Medium-range Weather Forecasts (ECMWF) and spectral nudging (SN) technique, the impact from spectral nudging (SN) technique drived by ECMWF data on the fine prediction of super typhoon Lekima (2019) in Zhejiang province are investigated by the Weather Research and Forecasting (WRF) model. The results show that: (1) The contribution of SN to track of Lekima is obvious, for instance, the maximum hourly track errors can be reduced about 80 km. (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 score of strong wind larger than 17.2 m/s is about 8% in mean and 20.8% in maximum. At the same time, the increase rate of TS scores of heavy rainfall with threshold as 50 mm/24h (100 mm/24h) reaches 11.8% (26.2%). (3) Further diagnosis illustrates that wind field spectral nudging can amend efficiently the west deviation of typhoon track and the over-prediction of strong wind as well as the heavy rainfall in southwest of Zhejiang province, which are related with the improvements in all atmospheric elements in troposphere, steering flow of Lekima, low-level wind field and resulted rainfall enhancement effect by local topography.