A COMPARISON OF GLOBAL TROPOSPHERIC TELECONNECTIONS USING OBSERVED SATELLITE AND GENERAL-CIRCULATION MODEL TOTAL OZONE COLUMN DATA FOR 1979-91

The total ozone column is well correlated with tropospheric fields suc h as the heights of the upper tropospheric geopotential surfaces and t hus it can provide useful information on temporal variability in the t roposphere. The global availability of long period satellite measureme nts of the total ozone column, taken by the TOMS instruments since 197 8, provides a valuable and independent data set for use in studies of seasonal and interannual climate variability. In this study, the globa l low-frequency seasonal teleconnections in the observed TOMS data fro m 1979-91 have been investigated using seasonal teleconnectivity maps and empirical orthogonal function analysis. They have also been compar ed with the results from a simulation made with the atmospheric GCM at Meteo-France, having prescribed observed sea surface temperatures for the same period. In the observed total ozone, strong ENSO-related wav e number one longitudinal dipole patterns are seen in both the tropics and in the Southern Hemisphere extratropics. The model shows much wea ker variability in total ozone yet appears to be able to capture simil ar teleconnection patterns in the tropics related to ENSO. In the SH e xtratropics, the model total ozone shows a strong wave number 3 respon se rather than the wave number one dipole seen in the observations. A wave number 3 response is also evident in the 200 hPa geopotential hei ght simulated by the model and in the NCEP analysis, and is consistent with the response in a linearised barotropic model forced in the Indo nesian region. The different responses in the modelled and observed to tal ozone, suggest that tropopause effect is not the major factor in t he SH extratropics, and it is likely that horizontal ozone transport a lso plays a role in this region. Despite a generally poor simulation o f the zonal mean total ozone, the model was able to capture the anomal ous strengthening of the SH stationary waves during austral spring of 1988, related to an intense stratosphere sudden warming.