| A detailed analysis of specific cases in 1998 and 2000 as well as a climatology spanning the period 1995--2004 are presented in this thesis 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 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). This TH, resulting from heating of the Tibetan Plateau, is responsible for a large part of the meridional mass circulation in the vicinity of the Indian Ocean. 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. It is also shown that the ozone distribution is strongly influence by the El Nino Southern Oscillation (ENSO). Results revealed that during La Nina column ozone is 5--10DU larger in 10--55°S. Additionally there is a 50° westward shift in the column ozone pattern during La Nina, with ∼20 DU enhancement in the 50°W--100°E band. Significant column ozone increase occurs poleward of South Africa during September and lies in a deep barotropic warm anomaly, associated with northeastward displacement of the South Indian Ocean High (SIOH) from South Africa. El Nino conditions display an enhanced SAH (35°S) while the AH (20°S) displays enhancement during La Nina conditions. |
