The variation of the total ozone column (TOC) before, during, and after tropical cyclones occurring in the pre-monsoon and post-monsoon periods over the Bay of Bengal and the Arabian Sea for the period 1997-2009 is presented. From the analysis, it is concluded that TOC decreases steadily before and during the formation of a cyclone, followed by a more or less increasing trend after dissipation of the cyclone. It is also observed that, when the cyclone reaches its peak intensity indicated by its maximum wind speed, there is a sudden fall in TOC over those regions where the cyclone has intensified. The observed variation of TOC is consistent with existing chemical and dynamical theories.
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