Stratospheric intrusion into the troposphere during the tropical cyclone Nilam (2012)

This article discusses different plausible mechanisms to account for the intrusion of dry ozone‐rich stratospheric air into the troposphere during the passage of the tropical cyclone Nilam‐2012. The present study shows that the overshooting convection associated with Nilam is found to be the prime candidate for the generation of turbulence in the vicinity of tropopause (VOT). In addition, the presence of strong updraughts and downdraughts in the VOT weakened the stability of the tropopause which allowed the dry ozone‐rich stratospheric air to penetrate downwards to the troposphere. Significant modulation of the tropopause structure is observed which is found to be accompanied by structures linked with shear instability. Concurrent ozone measurements also indicate the intrusion of stratospheric air mass into the upper and middle troposphere.