Observation of dominance of swells over wind seas in the coastal waters of the Gulf of Mannar, India

Abstract

Abstract. Wind seas typically dominate over swell seas in coastal gulfs. Waves measured at a location having a water depth of 12 m in the near-shore waters of the Gulf of Mannar during a 1-year period (1 May 2015 to 30 April 2016) are used to examine the predominance of wind seas and swells through spectral characterization. The study shows that even though the location is in a gulf, the annual average value ( ∼  0.84 m) of the significant wave height in this area is comparable to that along the coastal waters of the Indian subcontinent, but the annual maximum value ( ∼  1.7 m) recorded is much less than that (3 to 5 m) observed in those regions. Also, large seasonal variations are not observed in the wave height. The waves of the study region are under the control of sea breeze, with the maximum in the late evening hours and the minimum in the early morning hours. A 5 % increase in the forcing wind field during the monsoon period improved the comparison statistics between the model wave height and the measured values. A total of 53 % of the surface height variance in the study area is a result of swells from the southeast and south, and the remainder are wind seas from the east and southeast.