Numerical Simulation of Tropical Cyclone Mora Using a Regional Coupled Ocean-Atmospheric Model

Tropical storms (TS) are highly sensitive to the behavior of nearby oceans, and the only way to improve their predictability is to include all the possible factors contributing to their genesis and motion. The present study evaluates the response of air–sea coupling on TS Mora, which occurred during the pre-monsoon season of 2017. Mora is simulated using a non-hydrostatic regional atmospheric modeling system coupled to a regional ocean modeling system model. The observations show a low-level Rossby wave in the atmosphere during the storm genesis. There was also evidence of increased sea surface height simultaneously in the form of a downwelling Kelvin wave at the west coast of the Bay of Bengal. The present study emphasizes the relationship between near-surface oceanic and atmospheric circulation patterns. We have tried to elucidate the process with the help of dynamical equations and model solutions. We also analyze the pivotal role of the atmospheric Rossby wave in the formation of the coastal Kelvin wave. The Kelvin wave seems to produce a warm pool required to form a low-pressure system, which further gave rise to the tropical storm Mora. The changes in the temperature and salinity profile within the ocean subsurface layers during storm passage are further used for inferences regarding the vertical structure of the upper ocean due to wind-generated mixing. The model analysis reveals that the ocean and atmospheric counterparts responsible for storm genesis are well recorded in the coupled model when compared to the observations. It was found that air–sea coupling in the model made it possible to realistically capture ocean and atmospheric responses.