利用海-气-浪耦合模式（COAWST）对北印度洋一次强热带风暴“Fani”(2019)过程的数值模拟

利用最新研发的区域海-气-浪耦合数值模式(Coupled Ocean-Atmosphere-Wave-Sediment Transport，COAWST)，对印度洋一次超强热带气旋“Fani” (2019)过程进行了数值模拟试验。“Fani” 4月26日从热带印度洋面上的低压扰动中生成，在移动北上的过程中逐渐增强为强热带风暴，并于5月3日在印度登陆，造成了严重的破坏。利用COAWST耦合数值模式，在印度洋区域设计了数值模拟试验，分析了“Fani”发展增强到登陆时间段(4月30日12时—5月3日12时)大气物理量场、海洋表面温度及通量场，以及海浪参数的相应变化。通过与International Best Track Archive for Climate Stewardship (IBTrACS)的实测风暴路径、强度数据，以及欧洲中心ERA5再分析资料对比结果表明:模式模拟“Fani”的移动路径与观测较为接近，但是在强度模拟上偏弱；大气地表2 m温度场、潜热和感热通量与ERA5再分析资料存在一定偏差，但模拟的海表面温度场强度和特征与ERA5再分析资料都比较接近；在强烈的热带气旋与海洋相互作用下，耦合模式给出在气旋发展阶段，海浪有效波高达到近10 m；数值试验结果表明耦合模式可以有效描述热带气旋-海洋之间的相互作用，对于印度洋强热带风暴具备一定的模拟能力。 

NUMERICAL SIMULATION OF SEVERE TROPICAL STORM FANI (2019) IN THE NORTHERN INDIAN OCEAN USING THE COAWST MODEL

In the present research, the extremely severe cyclonic storm Fani (2019) is studied by using the recently developed Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) model. Fani was originally formed from low depression over the Indian Ocean on April 26, and rapidly intensified into a severe tropical cyclone. It made landfall in India on May 3, causing severe damage. Using COAWST, we configure a regional numerical experiment to simulate the development and landfall process of Fani (April 30 12: 00—May 3 12: 00 UTC), and investigate the atmospheric and oceanic parameters as well as significant wave height. The results are compared with the measured storm track and intensity data from the International Best Track Archive for Climate Stewardship (IBTrACS) and the ERA5 reanalysis data. The results show that the movement path of Fani simulated by the model is close to the observation, but the simulated intensity is weaker. The simulated 2m temperature, latent heat and sensible heat flux are slightly different from the ERA5 reanalysis data, but the simulated intensity and characteristics of the sea surface temperature field are close to ERA5 reanalysis data. Significant wave height of 10m is obvious during the whole process of Fani, and this strong tropical cyclone-ocean interaction has been well modeled, which reveals the large potential of COAWST to model tropical cyclones over the Indian Ocean.