A three-dimensional mechanistic ozone transport model: Applications to midlatitude trends and 11-year variability

Abstract

Thirteen years of satellite-based total ozone measurements, extending from January 1979 through December 1991, are analyzed with a multiple regression statistical model to isolate the components of interannual variability associated with (1) linear trends and (2) the 11-year variation in solar ultraviolet irradiance. Lower stratospheric temperature and geopotential height data obtained from satellite- and ground-based sources are analyzed in similarly, providing a comprehensive assessment of the interannual variability in the lower stratosphere over the 1979-1991 period. The results of the statistical analyses indicate coherent variations in ozone, temperature, and geopotential height at extratropical latitudes in NH winter which are related to both the trend and solar-cycle components; the amplitudes of these variations exhibit pronounced spatial dependences. A three-dimensional mechanistic ozone transport model is used to describe the spatial distribution of total ozone in NH winter using observed lower stratospheric temperature and geopotential height fields. Application of this model on a year-to-year basis demonstrates that a large percentage of the observed interannual variability in the spatial distribution of total ozone is directly associated with changes in the dynamical structure of the lower stratosphere. The influence of dynamical variability on zonal mean total ozone is also investigated using an empirical approach. From the results of the observational and modeling studies, it is concluded that changes in the dynamics of the lower stratosphere over the 1979-1991 period have contributed significantly to the observed total ozone trends in the Northern Hemisphere. In contrast, the observed variability in total ozone associated with the 11-year solar cycle could not be explained in terms of a systematic variation in the dynamical forcing of the lower stratosphere in-phase with the 11-year cycle.