Characteristics of individual surface waves measured by moored buoys in the coastal waters of the eastern Arabian Sea

Abstract

In this study, the characteristics of the individual surface waves in the eastern Arabian Sea over one year are examined based on the measured time-series data using Waverider buoys at four locations covering ~500 km of the western Indian coastline. At all locations, the number of waves is high during the non-monsoon compared to the monsoon period (June-September). Number of waves in a year is higher in the northern location (~6,417,657) than in the southern locations (~5,497,168) since comparatively more short-period waves are observed in the north. Maximum wave height varied from 7.0 to 7.6 m, and the steepness of the largest waves varies from 0.056 to 0.082 at different locations and is much smaller than the wave breaking limit. Number of short-period waves observed is higher than the long-period waves at all locations except in the monsoon, when a significant number of intermediate-period waves are present. The mean wave steepness of the 30-min record is ~22% higher than the conventionally reported significant wave steepness based on mean wave period. Hilbert-Huang transform method is used to detect the freak wave and analyze the abnormal wave group structure. It is observed that freak wave occurrence is high during the monsoon