Observational perspective of SST changes during life cycle of tropical cyclones over Bay of Bengal

Sea surface temperature (SST) plays a significant role in tropical cyclone (TC) formation and intensity evolution, while at the same time, TC induces SST changes during its life cycle. This work deals with the TC-induced SST changes associated with 21 TCs of Bay of Bengal (BoB) during 2006-2013. The SST analyses obtained from National Centre for Oceanic Information Services (INCOIS-SST) and real-time global SST (RTG-SST) are used along with buoy observations. Initial analyses reveal that INCOIS-SST is consistently better than RTG-SST with a good correlation and least root-mean-square error for both post- and pre-monsoon seasons. Overall results demonstrated that mean SST cooling decreases with increased translation speed of TCs within a radius of 50, 100 and 200 km from its centre. Further, a maximum SST cooling of similar to 2 and similar to 1.8 degrees C is noticed in pre- and post-monsoon, respectively, within the radial distance of 50-100 km from centre for slow-moving TCs, 1.2 and 1.0 degrees C for moderate and 0.9 and 0.7 degrees C for fast-moving TCs. The TCs formed over the southern BoB have a greater SST cooling up to 200 km radial distance followed by those formed over central and northern BoB in pre- and post-monsoon; however, the magnitudes of cooling in pre-monsoon seasons are greater than post-monsoon season. The minimum cooling over northern BoB may be attributed to the strong haline stratification as compared to the central and southern BoB during both seasons. However, there is a higher magnitude of stratification in post- compared to pre-monsoon, which might play a significant role in lesser SST cooling in post-monsoon season compared to pre-monsoon season.