Trends in wind-wave climate over the head Bay of Bengal region

Abstract

The average population density is significantly higher along the nearshore coastal zones compared to inland areas. Therefore, proper assessment and evaluation of the impact of climate change on coastal belts has immense societal benefits. The head Bay region located in the north Indian Ocean is a thickly populated area and highly vulnerable to threats from sea-level rise and extreme weather events. In this study, the wave climatology for the north Indian Ocean specifically covering the head Bay region was examined, utilizing the past 21 years of satellite altimeter data for the period ranging from 1992 to 2012. In addition, the study also examines the significant wave heights obtained from the WAVEWATCH-III (WW3) model to substantiate and evaluate the findings of the observed variability from altimeter records. The study used daily altimeter data from eight satellite missions to understand the annual and seasonal variability in wind speed and significant wave heights for the head Bay region. The annual distribution of these parameters follow the climatology, whereas the percentage variability in both wind speed and significant wave height show a clear contrasting trend exhibiting a zonal dipole. The study establishes the fact that the responsible mechanism for this contrasting trend is the variations in mean sea level pressure over the head Bay region. In addition, a comprehensive analysis using empirical orthogonal function (EOF) shows that the second mode that represents the inter-seasonal variations substantiates the trend observed in the percentage distribution of these parameters. Interestingly, the study clearly signifies that trends in both wind speed and significant wave height was lower for the western side, unlike that noticed over the eastern portions in the head Bay of Bengal region.