Role of external factors in the evolution of the ozone layer and stratospheric circulation in 21st century
Abstract. The chemistry-climate model (CCM) SOCOL has been used to evaluate the contributions of the main anthropogenic factors to the simulated changes of ozone and stratospheric dynamics during the 21st century. As the main anthropogenic factors we consider the atmospheric concentration of the greenhouse gases (GHG), ozone depleting substances (ODS) and sea surface temperature and sea ice (SST/SI). The latter is considered here as an independent factor because the majority of the CCMs prescribe its evolution. We have performed three sets of "time slice" numerical experiments for the years 2000, 2050, and 2100 taking into account all factors separately and all together. The total column ozone increase during the first half of the 21st century is caused by the ODS, especially in the middle and high latitudes of both hemispheres. In the tropics and the extra tropical region of the Northern Hemisphere (NH) the SST/SI forcing plays a very important role in the evolution of atmospheric ozone during the second half of the 21st century. The GHG affect the temperature and ozone mainly in the upper stratosphere and in the lower stratosphere of the high latitudes of the Southern Hemisphere (SH). In the lower tropical stratosphere of the NH, the long-term changes of the temperature, zonal wind and the meridional circulation are controlled mainly by the SST/SI. The strong contribution of the SST/SI to the ozone and circulation changes in the future implies that some differences between the results by different CCMs could be caused by the applied SST/SI rather than by the CCM's deficiencies. We suggest taking this issue into account for the planning of the future model evaluation campaigns.