Spectral Wave Characteristics over the Head Bay of Bengal: A Modeling Study
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Information on spectral wave characteristics is an essential prerequisite for ocean engineering-related activities and also to understand the complex wave environment at any given location. To the best of our knowledge, there are no comprehensive studies attempted so far to study the wave spectral characteristics over the head Bay of Bengal, a low-lying deltaic environment. The present study is an attempt to describe the spectral characteristics of wave evolution across different locations over this deltaic region based on numerical simulations. Therefore, it implements a multi-scale nested modeling approach using two state-of-art wave models, WAM and SWAN, and forced with ERA-Interim winds spanning the year of 2016. Model-computed integrated wave parameters are validated against wave rider buoy data as well as remotely sensed SARAL/AltiKa and merged altimeter data. Analysis of the monthly averaged one-dimensional spectrum reveals a single peak during the southwest monsoon and existence of double peaks from November to January, and occasionally up to March. Variance energy density undergoes inter-seasonal variation and attains its maxima during the month of July. Transformation of swell wave energy as a function of depth is found to be mostly associated with physical processes such as wave-bottom interaction and attenuation by opposing winds during the northeast (NE) monsoon. Fetch restriction for the evolution of wind seas (from the NE), modification in wind shear stress by opposing swells, and bottom effects remarkably contribute to the reduction in wind sea energy at shallow water depths. This study indicates that the influence of swells is higher along the eastern side of the basin as compared to the western side, and marginally higher variance is also observed over the east except during February–April. The two-dimensional wave spectra exhibit differential wave systems approaching from various directions attributed to a reflected swell system from the south-southeast throughout the year, southwest swells, reversing wind seas following local winds, and reflected wind seas from the land boundary.
KeywordsHead Bay of Bengal SWAN WAM wave spectrum wave transformation
The authors sincerely thank the Ministry of Human Resources Development (MHRD), Government of India for the financial support. This study is conducted as a part of the Mega Project “Future of Cities” under the module ‘Effect of Climate change on local sea level rise and its impact on coastal areas: Kolkata region as a pilot study’ supported by MHRD at IIT Kharagpur. The authors are grateful to the Indian National Centre for Ocean Information Services (INCOIS), Ministry of Earth Sciences, Hyderabad, for providing the waverider buoy data.
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