Trends in surface wind speed and significant wave height as revealed by ERA-Interim wind wave hindcast in the Central Bay of Bengal

Abstract

The Arabian Sea and Bay of Bengal (BoB) regions are special interested sea areas in the Northern Hemisphere with large seasonal variability. This study focused on the long-term wind and wave in the central BoB from 1979 to 2012 based on the ECMWF ERA-Interim reanalysis data sets. Data were validated with the nearest available buoy data for the years 2003, 2004 and 2005, and good correlation was observed (root mean square error ≈ 0.17–0.43 m). A clear seasonality was noted with intensified wind and waves during the southwest monsoon season. We observed statistically declining trends in the mean and extreme wind speed (90th percentile) with increasing trend in extreme significant wave height (SWH). Seasonal analysis also investigated and found that the stronger events/winds during the southwest (SW) monsoon season are weakening. Conflicting trends in the wind and wave height were mainly due to the swell dominance at the region which was identified by the separate trend analysis of wind-sea and swell height. The area average analysis is carried out to investigate the sensitivity of the identified trend results for the point location and found similar trends for extreme wind speed and SWH. The high (>5 m) annual maximum SWH in the study area was attributed to the influence of tropical cyclones in the BoB, and all of these high waves occurred before 1996 indicating that the influence of tropical cyclones in the study area decreased after 1996.