Regional wise characteristic study of significant wave height for the Indian Ocean

A proper knowledge and understanding of wind-wave characteristics and its variability on basin, regional and local scales have profound importance and practical applications in marine related activities, ocean engineering, and coastal zone management. The present study deals with the comparison of synoptic annual trends derived from space borne measurements (1992–2016), ERA-5 (1992–2018), and NCEP WWIII global run (1997–2018), monthly and seasonal wave climatology, characteristics of the annual cycle in regional basins and monthly trends of wind-wave climate on a pentad scale. Evaluation of wind-wave characteristics was performed for sub-divided domains of the IO. Further, the wave heights were segregated into percentile ranks (from 99th to 10th) by which a detailed analysis was carried out at the regional scale. Analysis of monthly and seasonal climatology signifies that the highest wave activity is observed in the extra tropical South Indian Ocean (ETSI) and the least in the Bay of Bengal. Higher percentile waves (99th, 95th, and 90th) in the ETSI are observed to be active for more than 6 months in a year. In the Arabian Sea, the maximum occurrence of 99th percentile waves (about 65%) is prominent during the month of July. An apparent pentad variation has been identified in the ETSI from 1997 to 2016 whereas, decadal variability in the north Indian Ocean (NIO) and Tropical South Indian Ocean for the lower percentile significant wave heights (25th and 10th percentiles). During the period 2007–2011, the IO experienced a considerable decreasing wave activity in all the sectors. The observed trends in annual maximum significant wave height for the ETSI and the annual mean significant wave height for the NIO are found increasing at a rate of 3.3 cm/year and 0.27 cm/year, respectively.