Marek Rogal

UW-Madison Department of Atmospheric and Oceanic Sciences

Dynamical Redistribution of Column Ozone in the Southern Hemisphere

Room 811 AO&SS, September 28, 2009, 3:30 PM

Abstract

A detailed analysis of specific cases in 1998 and 2000 as well as a climatology spanning the period 1995-2004 are presented in order to explain the influence that the dynamical regimes of the Upper Troposphere Lower Stratosphere region exert on the distribution of the Column Ozone in the Southern Hemisphere (SH). This study, reinforced with modeling experiments conducted using the University of Wisconsin Nonhydrostatic Modeling System (UW-NMS), has shown the extent to which the Tibetan Plateau and convection over Southeast Asia, which produces large anticyclones, namely the Tibetan High (TH) and Australian High (AH), shape the wave structure and the ozone distribution in the SH during the winter to spring transition period. It is found that a strong AH (southern part of the "Gill [1980] solution" to off-equatorial transient heating due to convection) leads to an "Ozone Croissant", while enhanced activity of the South African High (SAH) and Indian Ocean High (IOH) produces the column ozone structure reminiscent of the Ozone Collar. Isentropic trajectories underscore the importance of crossequatorial flow from the TH in modulating the AH and anticyclones over the Indian Ocean (IOH). The outflow associated with convectively-driven pair of anticyclones (TH and AH) was shown to be a major factor in the maintenance and modulation of the Australian Subtropical Westerly Jet located immediately poleward of the AH. The influence of El Nino Southern Oscillation (ENSO) on the ozone distribution is also analyzed.