The response of ocean parameters to tropical cyclones in the Bay of Bengal

The Bay of Bengal (BoB) exhibits notable seasonal variations in tropical cyclone heat potential (TCHP), barrier layer thickness (BLT) and sea-surface temperature (SST). These parameters also undergo profound changes in the presence of tropical cyclones (TCs). The composite structures of these ocean parameters as a function of the season of TC formation, intensity, and translation speed are unknown and are developed in the present study. Composite structures are examined based on 1,222 instantaneous samples from 83 TCs during 2003–2016 using INCOIS-GODAS analyses. A BLT of 10–30 m and TCHP of 40–80 kJ/cm2 favours TC intensification in the central BoB. The multivariate regression of BLT and TCHP appears to be better for TC intensity up to 64 knots and is highly underestimated for the stronger TCs (>64 knots). The TC right-rear sector experiences significant changes in TCHP anomaly (TCHPA) as the intensity increases. The TCHPA ranges ∼10–15, ∼20–25 and ∼25–30 kJ/cm2 when a TC is at Cyclone Storm (CS), Severe Cyclonic Storm (SCS) and Very SCS (VSCS) stages respectively. The maximum TCHPA is generally aligned along the TC track during the post-monsoon season. Slow-moving TCs produce maximum TCHPA cooling of ∼20 kJ/cm2 within 250 km storm radius in the rear sector, while it is less and away from the storm centre for normal and fast-movers. The seasonal changes showed opposite relations between BLT and TCHP from pre- to post-monsoon seasons during the TC intensification. TC-induced SST cooling is maximum (∼0.5–1.2 °C) in the inner core for the strong (VSCS and above) and slow-moving TCs. The cooling decreases with an increase in the translation speed and is more pronounced in the pre-monsoon season. This study provides a baseline to verify and understand the limitations of the models, and also develop a climatological perspective of BoB TCs.