Hourly maximum individual wave height in the Indian shelf seas—its spatial and temporal variations in the recent 40 years

Abstract

The spatial and temporal variability of the high individual wave heights, which pose a hazard in India’s shelf seas, has not been investigated. In this study, the spatial and temporal variation of hourly maximum individual wave height (Hmax) in the Indian shelf seas is examined based on 40 years ERA5 Re-Analysis data from European Centre for Medium-Range Weather Forecasts. Waverider buoy data from five locations are used to assess ERA5 Hmax. The variability of Hmax in different temporal scales; daily, monthly and interannual and their linkages with major ocean-atmosphere coupled interaction in the Pacific and the Indian Ocean are presented. Wave climatology throughout India’s western shelf seas shows average Hmax exceeding 2 m during most of the year. Maximum Hmax in the western shelf seas is during May–July, whereas in the southern tip and the eastern shelf seas are during the tropical cyclones and are either in October–December or May. Maximum Hmax is 17.94 m, and it occurred at the northern Bay of Bengal on 25 May 2009 during the passage of tropical cyclone Aila. Spatial variations in Hmax between locations spaced at 1.5° latitude are less than 10% in the northwestern and southeastern shelf seas, but large variations (~ 28%) are in the southwestern and northeastern shelf seas. Annual mean Hmax shows contrasting trends when data for 1979 to 2018 and 1992 to 2018 is considered. Indian Ocean Dipole influence on the Hmax suggests negative correlations in the western shelf seas and positive correlations in the eastern shelf seas. The correlation with climate indices is similar for both significant wave height and Hmax.