Surface and Sub-surface Ocean Response to Tropical Cyclone Phailin: Role of Pre-existing Oceanic Features

The upper oceanic thermal response induced by Tropical Cyclone Phailin (9-14 October 2013) under the influence of East India Coastal Current (EICC) and a cyclonic eddy is investigated and contrasted with the response from open ocean region using a high-resolution HYbrid Coordinate Ocean Model simulation. There is significant cooling (7 degrees C) inside the cold core eddy and negligible cooling (0.5 degrees C) within the EICC region characterized by the shallow and deeper thermocline, respectively. Our analysis of mixed layer heat budget terms showed that the horizontal advection plays a significant role in determining the temperature tendency for the location within the EICC, in contrary to the general dominance of vertical processes as reported in previous studies during the cyclone period. The analysis for the locations inside eddy and open ocean concurs with the previous studies showing the dominance of vertical processes toward the temperature tendency. Further, near the coast, the surface cooling is minimal compared to the subsurface cooling, dominantly seen between 50- and 100-m depth. This disparity indicates that the factors responsible for the surface temperature anomalies are different from those of subsurface. Our analysis of thermal signatures after the passage of cyclone showed that the EICC and cyclonic eddy contribute to the faster advection of cold wake and recovery of sea surface temperature to the prestorm state.