Previous multiple regression analyses of the solar cycle variation of stratospheric ozone are improved by (1) analyzing three independent satellite ozone data sets with lengths extending up to 25 years and (2) comparing column ozone measurements with ozone profile data during the 1992–2003 period when no major volcanic eruptions occurred. Results show that the vertical structure of the tropical ozone solar cycle response has been consistently characterized by statistically significant positive responses in the upper and lower stratosphere and by statistically insignificant responses in the middle stratosphere (∼28–38 km altitude). This vertical structure differs from that predicted by most models. The similar vertical structure in the tropics obtained for separate time intervals (with minimum response invariably near 10 hPa) is difficult to explain by random interference from the QBO and volcanic eruptions in the statistical analysis. The observed increase in tropical total column ozone approaching the cycle 23 maximum during the late 1990s occurred primarily in the lower stratosphere below the 30 hPa level. A mainly dynamical origin for the solar cycle total ozone variation at low latitudes is therefore likely. The amplitude of the solar cycle ozone variation in the tropical upper stratosphere derived here is somewhat reduced in comparison to earlier results. Additional data are needed to determine whether this upper stratospheric response is or is not larger than model estimates.

Understanding the dynamical relationships between low frequency forcings and the interannual variability of the Earths atmosphere is critical for accurate extended-range forecasts and climate prediction. This thesis investigates possible dynamical couplings between the stratosphere and troposphere by implementing lagged multivariate linear regressions. These regressions were chosen to untangle the separate responses of distinct atmospheric forcings upon zonal mean climate variability. The regressions incorporate monthly meteorological data with indices of four dominant forcings of low frequency atmospheric variability: the El Nino Southern Oscillation, the Quasi-Biennial Oscillation, the 11-year solar cycle, and volcanic activity. The analysis uses data from both the NCAR/NCEP and ECMWF reanalyses for two distinct time periods to expose possible satellite measurement influences. One period consists of all data since 1958, while the other period includes only data since 1979, a period of extensive satellite observations. Diagnostic tools include piecewise potential vorticity inversions, an assessment of anomalous Eliassen-Palm fluxes, stream function analyses, and general circulation model diagnoses. The examination reveals robust patterns associated with each forcing, consistent with existing theories in climate dynamics of the coupling mechanisms between the stratosphere and the troposphere. To better predict climate variability, however, the next step is to investigate the nonlinearities known to play an important role in this system.

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This thesis addresses the parameterisation of chemical and dynamical processes in the Antarctic stratosphere. Statistical models for the inter- and intra-annual variability in Antarctic stratospheric ozone depletion were developed based on theory and an understanding of the coupling of dynamics and chemistry in the atmosphere. It was confirmed that the primary driver of the long-term trend in the severity of the Antarctic ozone hole is halogen loading in the stratosphere. The year-to-year variability in ozone mass deficit, a measure of the severity of Antarctic ozone depletion, could be described by a linear combination of South Pole temperatures and midlatitude wave activity. A time lag of two weeks between wave activity effects and ozone depletion indicates the predictive capability of meteorological parameters for seasonal projections of the severity of the Antarctic ozone hole. The statistical model describing the inter-annual variability in ozone mass deficit was regressed against observations from 1979 to 2004. The resulting regression coefficients were applied to South Pole temperature and wave activity fields from 28 chemistry-climate models. This analysis indicates a slight increase in the year-to-year variability in the severity of Antarctic ozone depletion. As a prelude to analysing the seasonal evolution of Antarctic ozone depletion, an improved ozone mass deficit measure was derived by replacing the constant 220 DU threshold with a seasonal varying pre-ozone hole background which leads to better capturing the true extent of the depleted ozone. Furthermore, it was shown that the new measure represents the chemical ozone loss within the Antarctic vortex provided that no mixing occurs through the vortex boundary. This new measure has many advantages over previous stratospheric ozone depletion indices. The conventional ozone mass deficit omits large amounts of depleted mass of ozone, and the onset of ozone depletion does not coincide with the timing of when sunlight first reaches areas of polar stratospheric clouds as expected from theory. Chemical ozone loss derived with a tracer-tracer correlation technique depends on ozone and passive tracer profile measurements which are not as readily available as the total column ozone fields required for the new ozone mass deficit presented in this thesis. As such, the new ozone depletion measure combines the simplicity of the old ozone mass deficit index with higher accuracy of the actual amount of chemically depleted stratospheric ozone. Furthermore, when applying the new definition of ozone mass deficit to chemistry-climate model outputs, model intercomparisons should become easier to interpret because biases in the models can be avoided. Based on theory and understanding of the coupling of chemistry and dynamics in the Antarctic stratosphere, two semi-empirical models were developed to describe the intra-seasonal evolution of chlorine activation and ozone depletion. Regression of the models against chlorine monoxide and ozone mass deficit from observations results in coefficients that capture key sensitivities in the real atmosphere. The seasonal evolution of ozone mass deficit can be described with these coefficients and readily available meteorological fields (temperature and wind fields). The predictive capability of these models was demonstrated for 2005 and 2006. Given temperature and wind fields, which for example can be obtained from general circulation models, these models can predict the size and depth of the Antarctic ozone hole. Important applications of the semi-empirical models could be chemistry-climate model validation by comparing the sensitivities from observations and models which may provide new insights into potential sources of differences in chemistry-climate model projections of Antarctic ozone depletion. Furthermore, projection of the inter-annual and intra-seasonal evolution of the Antarctic ozone hole into the future can help to assess the potential recovery of the Antarctic ozone hole.