新一代区域海-气-浪耦合台风预报系统

依托国家重点基础研究（973）计划项目"上层海洋对台风的响应和调制机理研究"，中国气象局上海台风研究所联合国家海洋局的相关单位，通过实施近海台风的外场观测科学试验、加强台风边界层（特别是海气相互作用）物理过程诊断分析及参数化方案等的研究，建立并改进了台风强度预报的海-气-浪耦合预报模式系统，并在此基础上发展了台风强度的集合预报技术，在历史典型台风个例和2016-2017年台汛期的业务化测试中表现出良好的预报性能。     

ASSIMILATION OF REAL OBSERVATIONAL DATA WITH THE GSI-HYBRID DATA ASSIMILATION SYSTEM TO IMPROVE TYPHOON FORECAST

A hybrid GSI (Grid-point Statistical Interpolation)-ETKF (Ensemble Transform Kalman Filter) data assimilation system has been recently developed for the WRF (Weather Research and Forecasting) model and tested with simulated observations for tropical cyclone (TC) forecast. This system is based on the existing GSI but with ensemble background information incorporated. As a follow-up, this work extends the new system to assimilate real observations to further understand the hybrid scheme. As a first effort to explore the system with real observations, relatively coarse grid resolution (27 km) is used. A case study of typhoon Muifa (2011) is performed to assimilate real observations including conventional in-situ and satellite data. The hybrid system with flow-dependent ensemble covariance shows significant improvements with respect to track forecast compared to the standard GSI system which in theory is three dimensional variational analysis (3DVAR). By comparing the analyses, analysis increments and forecasts, the hybrid system is found to be potentially able to recognize the existence of TC vortex, adjust its position systematically, better describe the asymmetric structure of typhoon Muifa and maintain the dynamic and thermodynamic balance in typhoon initial field. In addition, a cold-start hybrid approach by using the global ensembles to provide flow-dependent error is tested and similar results are revealed with those from cycled GSI-ETKF approach.     

毫米波雷达在台风外围云系研究中的应用

为评估台风条件下毫米波雷达的探测表现,利用上海2018年和2019年4个台风影响期间的毫米波雷达数据,结合雨滴谱仪、静止卫星、S波段天气雷达等资料,探讨了利用毫米波雷达研究台风外围云系的可能性。结果表明：毫米波雷达探测台风外围区域具有良好的性能,对于云降水结构的垂直探测具有一定应用潜力;在降水强度低于5mm·h-1时雷达对于云顶高度的探测较为准确;提出一种融化层亮带判别方法,亮带识别结果与探空观测一致。对比毫米波雷达与S波段天气雷达降水强度反演,结果显示利用毫米波雷达衰减特征能够实现降水强度廓线的反演,但需要对存在显著雨滴碰并增长的降水进行识别并订正,可为毫米波雷达探测台风外围云系提供参考依据。