Abstract
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.
Highlights
Zubov et al.: Evolution of the ozone layer and stratospheric circulation but the majority of the chemistry-climate model (CCM) involved in the assessment of the ozone layer evolution exploit SST/SI distribution prescribed from atmosphere–ocean general circulation models (Morgenstern et al, 2010)
The main external factors (GHG, ozoInnestarnudmcelimnatateticohnanges throughsubstances (ODS), SST/SI) affect the composition and dynamics of the atmosphere by a multitude of the physical and chemical mechanisms: an additional heating and cooling of the atmospheric air and surface, changes of the gas-phase and heterogeneous chemical reaction rates, changes of the atmospheric circulation followed by alteration of the gas transport and others
Our results suggest that such a strong increase of Brewer–Dobson circulation (BDC) intensity is caused by the applied SST changes from MPI-OM model, rather than simulated by the CCM in response to changing concentrations of greenhouse gases (GHG) and ODS
Summary
The simulations discussed below have been performed using the global three-dimensional CCM SOCOL version 2.0. The CCM SOCOL consists of the middle atmosphere version of the European Center/Hamburg Model (MA-ECHAM4) (Manzini et al, 1997) and the three-dimensional chemistry-transport model (CTM) for the Evaluation of Ozone Trends (MEZON) (Egorova et al, 2003). The CCM SOCOL was applied to investigate the influence of the shortwave solar irradiance variability during the 11-year solar cycle on the composition and dynamics of the middle and lower atmosphere (Egorova et al, 2004) and to analyze the additional heating of the polar lower stratosphere from galactic cosmic rays and its plausible impact on atmospheric ozone, temperature, and circulation (Zubov et al, 2005, 2006). To verify and increase the confidence of the model results the CCM SOCOL participated in the International Chemistry–Climate Model Validation Activity (CCMval-1,2) of the Stratospheric Processes and Their Role in Climate (SPARC) program. The results published in the final CCMval-2 report (SPARC CCMVal, 2010) allow us to conclude that CCM SOCOL 2.0 is comparable to most of the other stratospheric CCMs
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