Remote sensing and in situ platform based study on impact of Bay of Bengal cyclones (Phailin, Helen, Lehar, and Madi) on ocean chlorophyll and associated physical parameters

Impact of four major cyclones: Phailin, Helen, Lehar, and Madi have been studied in terms of changes in ocean productivity utilizing Indian satellite Oceansat-2 ocean color monitor and MODIS-Aqua data during October–December 2013. The 8-day and monthly composite chlorophyll images have been generated owing to the pre-, during, and post-stages of four cyclones; out of which, three were very severe cyclonic storms and the Helen was severe cyclonic storm. The chlorophyll concentration increased two- to threefolds due to the aftereffect of cyclone in the coastal water, and the concentration was very high (around 2–3 mg/m3). To understand the possible links of cyclones to cooling and upwelling, MODIS-Aqua sea surface temperature (SST) images have been processed. The SST images have shown the cooling effect near the cyclone track pass, over Bay of Bengal. The cooling was observed by 2–3 degree Celsius during the above cyclones. To understand the in situ surface water and water column salinity and temperature variability, the Argo float data are plotted and interpreted. The surface contour shows the lowering of salinity and temperature with effects of cyclones. In addition, the Argo depth profile data have shown possible mixed layer deepening in few profiles around halocline and thermocline depths. This study will be useful for mapping potential fishing zone, ocean biogeochemistry and other useful applications and research.