Effect of May 2003 tropical cyclone on physical and biological processes in the Bay of Bengal

Satellite observations are beginning to show the remarkable effects of tropical cyclones on upper ocean temperature and chlorophyll concentration. We use weekly, 4 km resolution chlorophyll-a and sea surface temperature (SST) from TERRA Moderate Resolution Imaging Spectroradiometer, weekly averaged SST at 0.25° resolution from Tropical Rainfall Measuring Mission Microwave Imager, modeled primary productivity (PP) from Goddard Space Flight Center and mixed layer depth generated by US Navy's Fleet Numerical Meteorology and Oceanography Center to study the response of upper ocean physics and biology to the passage of a tropical cyclone in the southern Bay of Bengal. Decrease in SST up to 5°C, associated with the deepening of mixed layer by about 12 m, was observed. Directly under the cyclone track, PP increased from its pre-storm value by up to $3800 mg C m^{-2} day^{-1}$, and chlorophyll-a concentration also increased. The increase in chlorophyll-a and productivity were not confined to the region under the cyclone track, but covered a much broader area, possibly due to forced coastal upwelling south of Sri Lanka. After the passage of the cyclone the SST slowly increased, and the chlorophyll decreased.