Simulation Experiments Of A Developing Extratropical Cyclone Process

The Zhejiang coastal waters are frequently influenced by developing extratropical cyclones after entering Sea (DECS) every year. DECS usually cause extreme gust and waves, which can bring about shipwrecks and fatalities. It remains a difficult problem in practical work to forecast the DECS. In this study, we discussed the characteristics of the DECS which influenced the Zhejiang coastal, and the Weather Research and Forecasting (WRF) model system, which is typically used in the regional meso-scale model prediction, is used to simulate a DECS process. Three experiments are conducted:the control run (without assimilation data), sensitive run (with assimilation of cloud drift wind data (CDWD), quality control is not conducted to the CDWD) and CDWD run (with assimilation of CDWD, quality control is conducted to the CDWD). The comparison of the three experiments shows that including the assimilation of CDWD can have positive impact on DECS prediction. The CDWD run results are very similar to the actual observation and can be used as the representation of the actual atmosphere. We examined the DECS-associated atmospheric field change at various levels, and analyzed the change of vorticity, divergence, humidity, vertical motion, and high-level jet stream. We discussed the forecasting focus of this type of mid-latitude cyclones and the possible approaches to improve the prediction accuracy.