Modeling of storm surges and wave heights during few cyclones over Bay of Bengal using uncoupled and coupled (ADCIRC+SWAN) models

Abstract

In this study, the uncoupled (ADCIRC) and a tightly-coupled SWAN (Simulating Waves at Near shore) + ADCIR (Advance circulation Model) models are used to estimate the storm surge heights along the east coast of India. four cyclones over the Bay of Bengal during 2013, viz; <em>Mahasen </em>( May 10-17 ), <em>Phailin </em>(October 8-14 <em>), Helen</em> (November 19-23) and <em>Lehar</em> (November 23-28),. Due to finite element nature of ADCIRC, the mesh (grid) structure was having variable spatial resolution with higher resolution (~5Km) near to the coast and 50 km offshore. The validation of simulated surges from both stand alone and coupled configurations was carried out using observations from tide gauges .The simulated wave heights were validated using observations from Ka-band Altimeter onboard SARAL(Satellite with ARgos and ALtiKa). It is found that the coupled model (ADCIRC+SWAN) performed well compared with the uncoupled model, in predicting the storm surges. The simulated maximum Water level for uncoupled (ADCIRC only) run that considers the astronomical and meteorological forcing was about 2.3 m, at Gopalpur coast (landfall point). The coupled model that considers additional wave radiation stress provides the maximum water level elevation as 3.0 m at the above location. The observed surge height close to this location was 2.9 m. The significant wave heights (SWH) estimated by the models are compared with the SARAL Altika data. More than 12000 observations are used for comparison, It is found that the correlation between the estimated and observed values of SWHs were high and significant in all the four cyclones and the highest correlation of 0.67 was observed in case of <em>Lehar</em>