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The mean strengths of the wintertime stratospheric polar vortices are known to be related to the phase of the quasi-biennial oscillation (QBO) in the tropical stratosphere from circulation statistics - the "Holton-Tan relationship". The principal topic of this thesis is improving understanding of the mechanism behind the QBO's influence. Following the example of previous studies, the QBO influence on the Northern Hemisphere (NH) extratropics on monthly time scales in an observational reanalysis is examined, and is shown to closely resemble the stratospheric Northern annular mode (NAM). It is argued that this may not be informative about the mechanism, as the response could be NAM-like for many different mechanisms. It is suggested that examining the transient response of the NH extratropics to forcing by the QBO would be much more informative, particularly on time scales of a few days. In a primitive equation model of the middle atmosphere, the long-term stratospheric NH response to imposed zonal torques is often found to be NAM-like under perpetual January conditions, with wave feedbacks making a very important contribution. However, the response in runs with a seasonal cycle is not NAM-like. Investigation of the transient responses indicates the wave feedbacks are qualitatively similar in each case but only strong enough under perpetual January conditions to make the long-term response NAM-like. This supports the hypothesis that feedbacks from large-scale dynamics tend to make the stratospheric response to arbitrary forcings NAM-like, and therefore indicates that the long-term response is not generally useful for understanding forcing mechanisms. Examining the short-term transient response to known torques is found to be more successful at inferring information about the torques than several other previously proposed methods. Finally, the short-term transient response of the NH extratropics to forcing by the easterly QBO phase in a general circulation model is found to be consistent with the proposed mechanism of Holton and Tan (1980), indicating that this mechanism plays a role in the Holton-Tan relationship.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The present PhD thesis analyzes the results obtained from the Total Ozone Column (TOC) monitoring conducted in the Southern Space Observatory - SSO (29.26 ° S, 53.48 °W and 488 m altitude) between 1992 and 2014 by three successive Brewer spectrophotometers (# 081, # 056 and # 167). First, the Brewer measurements were compared with TOMS (Total Ozone Mapping Spectrometer) and OMI (Ozone Monitoring Instrument) satellites obtaining excellent agreement. In addition, was determined that the seasonal TOC variability is dominated by the annual cycle, with a minimum of ~ 260 DU in April and a maximum of ~ 295 DU in September. The Quasi-Biennial Oscillation (QBO) is the main mode of interannual variability being approximately in antiphase with the QBO index. Next, 58 events of the influence of the Antarctic Ozone Hole on the SSO station was identificate in the period between 2005 and 2014. This events occurred on average 5.8 ± 3.51 times per year, with a mean reduction of TOC by Brewer' of -7.04 ± 2.97% and by OMI of -7.66 ± 3.11 respectively. Analyzing the ozone profiles from AURA/MLS (Microwave Limb Sounder) satellite, the average isentropic level for maximum reduction is 644.68 ± 158.59 K, with a mean reduction of 15.39 ± 6.47%, being October the month of greatest occurrence (18 events). The events were separated into three categories: TOC intensity reduction, height of the ozone reduction lamina in AURA/MLS satellite and the dynamic characteristic of Polar Filament or Polar Tongue through the application of Dybal (Dynamical Barrier Localization) code in the potential vorticity (PV) fields from MIMOSA (Modélisation Isentrope du transport Mésoéchelle de l'Ozone Stratosphérique par Advection) model. The events with a dynamic feature of Polar Tongue (20,68%) occurred more frequently in October, with medium intensity and in the medium stratosphere, while events of dynamic characteristic of Polar Filament (79,31%) occurred more frequently in September, also with medium intensity and in the medium stratosphere. / A presente Tese de Doutorado analisa os resultados obtidos a partir do monitoramento da Coluna Total de Ozônio (CTO) realizado no Observatório Espacial do Sul – OES (29,26 ° S, 53,48 ° e 488 m de altitude) entre 1992 e 2014 através de três sucessivos espectrofotômetros Brewer (# 081, # 056 e # 167). Primeiramente, as medidas dos Brewers foram comparadas com observações dos instrumentos de satélite TOMS (Total Ozone Mapping Spectrometer) e OMI (Ozone Monitoring Instrument), obtendo elevados valores de R2 (0,88 e 0,93, respectivamente). Além disso, foi determinado que a variabilidade sazonal da CTO é dominada pelo ciclo anual, com um mínimo de ~260 DU em abril e um máximo de ~295 DU em setembro. A Oscilação Quasi-Bienal (QBO) é o principal modo de variabilidade interanual estando aproximadamente em antifase com o índice QBO. Em seguida é apresentada a identificação da ocorrência de 58 eventos de Influência do Buraco de Ozônio Antártico sobre a estação do OES no período entre 2005 e 2014, os quais ocorreram em média 5,8 ± 3,5 vezes por ano, com redução média da CTO de Brewer e OMI de -7,04±2,9% e 7,66±3,1 respectivamente. Analisando os perfis de ozônio do satélite AURA/MLS (Microwave Limb Sounder), observa-se que o nível isentrópico médio para a máxima redução é de 644,6±158,5 K com redução média de 15,3±6,4%, sendo outubro o mês de maior ocorrência (18 eventos). Os eventos foram separados em categorias: Intensidade da redução da CTO, altura da camada de redução no perfil do ozônio do satélite AURA/MLS e a característica dinâmica de Filamento Polar ou Língua Polar através da aplicação do código Dybal (Dynamical Barrier Localisation) nos campos de vorticidade potencial (PV) do modelo MIMOSA (Modélisation Isentrope du transport Mésoéchelle de l'Ozone Stratosphérique par Advection). Os eventos com característica dinâmica de Lingua Polar (20,68%) ocorreram com mais frequência no mês de outubro, com intensidade média e na média estratosfera, enquanto que eventos de característica dinâmica de Filamento Polar (79,31%) ocorreram com mais frequência no mês de setembro, também com media intensidade e na média estratosfera.