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Tropical cyclones when on land create havoc, but over the oceans they can trigger a very strong biological response, giving rise to phytoplankton blooms. The Super Cyclone (TC) 05B that occurred during October 25-29, 1999, in the Bay of Bengal over the tropical Indian Ocean was one of the most significant tropical cyclones on record to affect India, with maximum winds of 240 km/h, and the worst since 1971. Using satellite data, it is found that this tropical super cyclone helped spawn a notable mesoscale phytoplankton bloom in the domain (17deg-20degN; 87deg-90degE), which persisted for over a month. The bloom spanned 440 km zonally and 330 km meridionally, enhanced the chlorophyll-a concentrations to a maximum of 10 mg/m3 and the net primary productivity by 200%. Furthermore, a cyclonic eddy over the bloom region is revealed from an ocean general circulation model simulation, helping the bloom to last for over month.
Date of Publication: Oct. 2008