Long-term changes of zonally asymmetric ozone and their effects on stratospheric temperature and planetary wave propagation

Long-term changes in the zonally asymmetric component of stratospheric ozone have been analyzed based on ECMWF Reanalysis (ERA-40) and satellite data (e.g. SAGE, GOME). For northern winter hemisphere, the decadal means of zonally asymmetric ozone show a strong decadal increase in stratospheric wave one structure with amplitudes of about 10% of zonal mean ozone during the 1990s. Model calculations with the GCM MAECHAM5 were carried out with and without the zonally asymmetric ozone component to investigate their effects on radiation, stratospheric temperature and planetary wave propagation from troposphere to lower mesosphere. The results reveal that the asymmetric ozone component induces significant stratospheric temperature changes increasing with height due to an increase in amplitude and a shift in phase of stratospheric wave one (e.g. strong declines of -4K at 50hPa and -8K at 0.1hPa in the region of the stratospheric polar vortex). In the stratosphere, we found also an induced shift of up- and eastward directed stationary wave trains from the eastern to the western hemisphere. Possible influences on tropospheric dynamics are discussed. The results illustrate the important influence of ozone-dynamics interaction, and suggest that the decadal changes in zonally asymmetric ozone may have contributed largely to observed stratospheric temperature trends.