Atmospheric and oceanic responses to Super Typhoon Mangkhut in the South China Sea: a coupled CROCO-WRF simulation

The South China Sea (SCS) is the largest marginal sea in the Northwest Pacific Ocean, and it encounters frequent typhoons. The atmosphere and ocean will create significant thermal and dynamic responses during the intense disturbance caused by typhoons. However, these responses have not been thoroughly investigated owing to the complicated marine environment. According to the satellite data, the SCS Basin was observed to have a strong sea surface temperature (SST) response to Typhoon Mangkhut, resulting in widespread SST cooling. A coupled model was used to investigate the atmospheric and oceanic responses to Typhoon Mangkhut. Best-track data, satellite SST, and ARGO measurements show that the coupled WRF-CROCO simulation displays better track, intensity, SST, temperature, and salinity profiles than those of the WRF-only simulation. Results show that the typhoon induced rightward intensifications in wind speed, ocean current, and SST. The following are some remarkable atmosphere and ocean responses: (1) the SST below the inner-core region is cooled by 1 °C, resulting in a 37%–44% decrease in wet enthalpy, and the central pressure is increased by ∼9 hPa. Therefore, the changes in SST below the inner-core region of the SCS Basin have a significant impact on air-sea fluxes under high-wind conditions; (2) the ocean boundary layer analysis shows that near-inertial oscillations on the right side of the typhoon track and a strong inertial current up to ∼2.28 m/s in the upper ocean were observed, which resonated with the local wind and flow field on the right side and induced strong SST cooling; (3) a decrease in SST decreased the moist static energy of the typhoon boundary layer, thereby weakening the typhoon’s intensity. The difference in equivalent potential temperature and sea surface pressure have a good correlation, indicating that the influence of moist static energy on typhoon intensity cannot be overlooked.