Ray, S.; Swain, D.; Ali, M.M.; Bourassa, M.A. Coastal Upwelling in the Western Bay of Bengal: Role of Local and Remote Windstress. Remote Sens.2022, 14, 4703.
Ray, S.; Swain, D.; Ali, M.M.; Bourassa, M.A. Coastal Upwelling in the Western Bay of Bengal: Role of Local and Remote Windstress. Remote Sens. 2022, 14, 4703.
Ray, S.; Swain, D.; Ali, M.M.; Bourassa, M.A. Coastal Upwelling in the Western Bay of Bengal: Role of Local and Remote Windstress. Remote Sens.2022, 14, 4703.
Ray, S.; Swain, D.; Ali, M.M.; Bourassa, M.A. Coastal Upwelling in the Western Bay of Bengal: Role of Local and Remote Windstress. Remote Sens. 2022, 14, 4703.
Abstract
Monsoon winds drive upwelling along the eastern coast of India during the south-west (SW) monsoons. These winds also provide alongshore windstress (AWS) resulting in positive cross-shore Ekman transport (ET) from March to the end of September. While instances of high ET and sea surface temperature based upwelling index (UI_SST) were observed along two parts of the coast: between Kashinagara and Kakinada in the north, and between Kavali and Point Calimere in the south. The UI_SST illustrated a much poorer agreement with local ET in the northern section, where the onset of UI_SST preceded the rise of ET and the subsidence of UI_SST signals occurred during a period of rising ET. Additionally, negative sea surface height anomalies (SSHAs), typically associated with coastal upwelling, were also missing through most of the upwelling period. A complex empirical orthogonal function (CEOF) analysis revealed two coherent modes of SSHA variation. The first mode showed a SSHA signature spatio-temporally coincident with the first upwelling and downwelling Kelvin waves closely associated with the equatorial zonal winds that drive them. The second CEOF mode, with a coastal SSHA pattern similar to the SSHA signatures of coastal upwelling, was associated with local offshore ET along the Indian east coast. The CEOF analysis exhibited the triggering of coastal upwelling in April and its suppression from June by coastally trapped Kelvin waves along the northeastern coast of India, while local AWS driven ET was the primary driver of coastal upwelling along the southeastern coast. The second CEOF mode also exhibited a coherent negative coastal SSHA signature excited by local AWS driven ET during the upwelling period. This study examined the spatio-temporal variability of premonsoon and SW monsoon coastal upwelling along the western Bay of Bengal and its relation to remotely forced coastal Kelvin waves.
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