A coupled model analyses on the interaction between oceanic eddies and tropical cyclones over the Bay of Bengal

Abstract

The Bay of Bengal (BOB) region of Indian Ocean is affected by numerous tropical cyclones during pre- and post-monsoon seasons when various eddies are generated in the central and western bay. Here, numerical simulations of few tropical cyclones (Aila, Laila, Phailin, Hudhud and Madi) that occurred in different seasons are carried out using an ocean atmosphere coupled numerical model, consisting of Weather Research and Forecasting (WRF) and Regional Ocean Modeling Systems (ROMS), to analyse the influence of eddies on tropical cyclone intensifications over the bay. The model is able to track the tropical cyclones with less error, while the central pressure and wind speed are underestimated. Also, the coupling process steer the cyclones to the observed track compared to standalone WRF model. The variations in simulated sea surface temperature and salinity are in agreement with the satellite and in situ measurements. During the passage of Phailin and Hudhud over the eddies, the cyclones intensified almost twice of their initial central pressure and wind (before interacting with eddies), which the model captured very well. The eddy feedback factor, which estimate the influence of warm eddies on tropical cyclones, is about 152% for Phailin and 90% for Hudhud. In the case of the pre-monsoon cyclones, Aila and Laila, the eddy feedback factor is estimated up to 36% and 21%, respectively. Madi cyclone lost its intensification up to 80% because of its interaction with a cold eddy. These predictions are comparable with that of the observations during the cyclone passage. Also it is noted that the warm eddy regions resulted in the maximum transfer of latent heat resulting in strong intensifications of the cyclones. Our study reveals that the eddies play an important role in the intensification and dissipation of BOB cyclones and understanding their nature can help in estimating the track and intensity of cyclones.