The impacts of mesoscale eddies on the modulation of typhoon-induced oceanic responses are important for understanding ocean dynamics. Satellite observations identified prominent ocean surface temperature and chlorophyll changes over the regions with mesoscale eddies after two sequential typhoons, e.g., Linfa and Nangka, in the South China Sea. The impacts of typhoons on the ocean surface were more prominent within cyclonic eddies than within anticyclonic eddies. The wind speed (translation speed) of Linfa was much larger (slower) than that of Nangka; thus, the changes induced by Linfa were stronger. However, the second typhoon easily generated mixing through the weak stratification induced by the first typhoon and impacted the upper ocean. The strong chlorophyll enhancement induced by Nangka was identified at a cyclonic eddy. Using a combination of reanalysis data, the depth of water origin (DWO) was applied to quantify the depth to which a typhoon’s impact could be exerted. Prominent changes were identified when the DWO reached the depth at which the temperature and nutrients differed from those within the mixed layer. This method can overcome the impacts of cloud coverage when examining a typhoon’s influence with remotely sensed data and offers a quantitative approach to determine the mechanisms responsible for typhoon-induced ocean surface changes.

The unique tropical storm (TS) Deliwe (2014) occurred in the northern Mozambique Channel on 17 January 2014 and turned right during its whole life cycle, moving south along the west coast of Madagascar Island. During the development of the TS, the anticyclonic eddies in the Mozambique Channel had an important influence on the intensity and track of Deliwe, which existed for months. In this study, multisource reanalysis, conductivity temperature depth (CTD) and Argo buoy data were used to investigate the mechanism of dynamics. The results showed that the anticyclonic eddies in the Mozambique Channel were a major cause of Deliwe strengthening, weakening and then deflection to the right. On 17 January, the maximum latent heat flux of anticyclonic eddy W1 reached 103.1 w/m². After Deliwe passed, the tropical cyclone heat potential (TCHP) of anticyclonic eddy W1 was significantly reduced by 3 kJ/cm². The mixed layer of anticyclonic eddy W1 was deeper than the surrounding waters, supporting the development of Deliwe. As the TS intensity decreased, the low-pressure center of 500 hPa moved above anticyclonic eddy W2, and the westerly wind belt moved northward to form a westerly trough of low pressure, which caused the TS to keep turning right and formed a unique TS track. This study provides a new understanding of the influence of marine anticyclonic eddies on the development of tropical cyclones (TCs) in the Mozambique channel.

A tropical storm (TS) Roanu occurred in northern Sri Lanka in 2016, which transported northwards along the west coast of the Bay of Bengal (BoB). During the development of the TS, ocean eddies on its track had an important effect on the intensity of Roanu. The dynamic mechanism was investigated with multisource reanalysis and Argo float data in this study. The results show that ocean eddies were the main reason why Roanu first enhanced, weakened, and then enhanced again. Warm eddy W1 supports the initial development of the TS, cold eddy C1 weakens Roanu, and warm eddy W2 continues to support Roanu. On May 19, 2016, the maximum average latent heat flux over W1 was 260.85 w/m², while that of C1 was only 200.71 w/m². After the passage of Roanu, the tropical cyclone heat potential (TCHP) of eddies significantly decreased. The TCHP of W1, W2, C1 and C2 decreased by 20.95 kJ/cm², 11.07 kJ/cm², 29.82 kJ/cm², 9.31 kJ/cm², respectively. The mixed layer of warm eddies deepened much more than that of cold eddies, supporting Roanu development. In addition, changes in potential vorticity (PV) values caused by the disturbance of eddies may also reflect changes in the TS intensity. This study offers new insights on the influence of ocean eddies in regulating the development of tropical cyclone (TC) in the BoB.