Ozone Variation during the Development of a Tropical Cyclone: Case Study

Abstract

The aim of this work was to study the variation in the total ozone column amount (TOC) during the life cycle of the tropical cyclone (TC) that occurred over the northwest Indian Ocean from 14 to 25 October 2008. This goal was achieved through examining the behavior of the tropical cyclone tilt under vertically varying background flows in association with the cyclone development. Thus, the vertical wind shear (VWS) was estimated as one of the most important dynamical parameters related to TC formation and intensity changes. Moreover, we estimated the variations in the daily values of TOC during the period of cyclone activity. We found that the magnitude of VWS increased during the growth period, and VWS weakened during the decay period. Anomalies of daily TOC were found to reduce steadily before and during the cyclone formation, followed by an increasing trend after the dissipation of cyclone. It was also found that during the development of the tropical cyclone, an outflow developed in the upper levels, having high velocities that extended beyond the tropopause up to the lower stratosphere. As a result, the lowest value of TOC during the tropical cyclone was due to a large amount of injected water vapor from the troposphere into the stratosphere through the convection processes. This was mostly photo-dissociated into OH and atomic O by deep solar radiation in the upper and lower stratosphere, leading to a severe reduction in stratospheric ozone.

Keywords

• total ozone column
• tropical cyclone
• tilt
• vertical wind shear
• cyclogenesis
• stratosphere-troposphere exchange