Estimation and Validation of Offshore Wave Characteristics of Bay of Bengal Cyclones (2008-2009)

Abstract

Offshore wave characteristics viz; significant wave height (Hs) and peak wave period (Tp) during cyclonic storms are important in planning and design of offshore structures, ship operations and other offshore activities. During June, 2008 to May, 2009 four cyclonic storm (CS) and one depression (D) originated over Bay of Bengal (BoB). In this paper, with the help of empirical formulae (Young's model, 1984; SMB method, 1984 and Sanil et al. (2003) we have estimated the offshore wave characteristics along the tracks of the four CS and one depression using the cyclone wind climate of Indian Meteorological Department (IMD). The spectral wave model of MIKE 21 is used to simulate wave characteristics of BOB while the observed wave characteristics off Gopalpur measured at 23 m water depth is used for validation. Various statistical parameters viz. root mean square error (RMSE), scatter index (SI), and correlation coefficient (R) are derived to inter-compare the observed, simulated and estimated results. The observed and simulated values of Hs show very good agreement (correlation coefficient of 0.86) while the agreement in case of wave period is relatively lower (R=0.55). Comparison between simulated and estimated Hs shows good agreement for Young's model and SMB method, while Sanil et al. equation shows over estimation as compared to simulation. Similar comparison for Tp shows good agreement with Young's model and Sanil et al. equation and over prediction for SMB method.