Spectral Modelling on the Characteristics of High Frequency Tail in Shallow Water Wave Spectra at Coastal Puducherry, East Coast of India

Abstract

About 8 years of measured wave spectra (June 2007–December 2014) off coastal Puducherry located in the east coast of India and bordering the Bay of Bengal were analyzed with an objective to understand the slope of the high frequency tail of the wave spectrum and to determine the occurrence of single peaked, double-peaked and multi-peaked spectra in varying sea states. The temporal and inter-annual variation of the spectral energy density over the years indicates marked variability and the study signifies that wave spectra were multi-peaked from June to October and predominantly double peaked during the rest of the year. Swell and wind sea components have been estimated from the wave spectra by separation frequency method. The analysis shows that swells dominate Puducherry coastal region not only during southwest monsoon (95%), but also during the post-monsoon (100%) and northeast monsoon season. The measured wave spectra were compared with numerical wave model outputs to attain a level of confidence with the buoy data. In addition, analysis on the slope of the high frequency tail of the wave energy spectra shows that its slope varied seasonally in the range of − 1.96 to − 3.27 at the coastal location. Further, the JONSWAP model fitted into measured wave spectra showed high discrepancy between the two, especially in the high frequency tail with Scatter Index ranging between 0.79 and 3.98. The correct slope for the high frequency or even whether a unique slope exists remains elusive for the ocean wave community.