Long-term seasonal inhomogeneity and recent patterns in air-sea conditions and tropical cyclone activities over the Bay of Bengal

The Bay of Bengal (BoB) covers about 0.7% of the world ocean area but produces almost 4% of the Tropical Cyclones (TCs) of the world. Moreover, about 75% TCs of the North Indian Ocean (NIO) generate in the BoB. The TCs in the BoB have pronounced seasonal variation and predominantly occur in two seasons, Pre-Indian Summer Monsoon (ISM, ~ 23%) and post-ISM (~ 65%). This study presents a quantitative analysis to discuss the seasonality in ocean, atmospheric conditions and the TC activities over the BoB using long-term (1982-2022) data. The quantitative statistical analysis also highlights the changing patterns of the air-sea and TC parameters in recent years (2001-2022). The results show that the air-sea conditions have a strong seasonal variation during pre- and post-ISM over the analysis period. In recent years, the air-sea conditions followed a strong changing pattern which leads the major shift in TC frequency, movements and intensifications. Overall, the study shows that the seasonal inhomogeneity in the upper ocean thermodynamics and atmospheric conditions trigger the seasonal variations in TC activity over the BoB. The upsurges in intensified TC activities over the BoB in the recent years is also reflected in the air-sea forcing conditions.