Assessment of input and dissipation source terms in the spectral wave model during tropical cyclones of varying intensity in Bay of Bengal

The vulnerability of the tropical cyclonic activities in the Bay of Bengal (BoB) domain are analyzed in terms of its destructive potential. The wave characteristics due to cyclones of varying intensities: Vardah, a Very Severe Cyclonic Storm (VSCS); Phethai, a Severe Cyclonic Storm (SCS); and Amphan, the Super Cyclonic Storm (SuCS) in BoB during 2016, 2018, and 2020 causing loss to human life and wealth, are investigated. The input-dissipation source term packages in the spectral wave models under tropical cyclones are studied through (i) integrated parameter, significant wave height, and (ii) individual source term analysis. In addition to the default linear drag coefficient in the wind input source term of van der Westhuysen et al. (2007), two nonlinear formulations of the drag coefficient are included to understand its influence on the source terms. The integrated parameters such as significant wave height are compared with buoy measurements, and the performance of the packages is ascertained through statistical error estimates. Energy contribution from the different source terms under various packages to generate the extreme significant wave height over the domain during the cyclonic period is established. The influence of the drag coefficient on the input source term is found to be pronounced.