Impact of large solar zenith angles on lower stratospheric dynamical and chemical processes in a coupled chemistry-climate model

摘要: Abstract. Actinic fluxes at large solar zenith angles (SZAs) are important for atmospheric chemistry, especially under twilight conditions in polar winter and spring. The results of a sensitivity experiment employing the fully coupled 3D chemistry-climate model ECHAM4.L39(DLR)/CHEM have been analysed to quantify impact SZAs larger than 87.5o on dynamical chemical processes lower stratosphere, particular their influence ozone layer. Although actinic small, concentrations significantly affected because daytime photolytic destruction is switched earlier, end night conversion Cl2 Cl2O2 into ClO stratosphere. Comparing climatological mean column values simulation considering up 93o with those run confined total reduced by about 20% Southern Hemisphere, i.e., hole "deeper'' if considered there 4 weeks more time destruction. This causes an additional cooling stratosphere (50 hPa) -4 K obvious consequences processes. In Northern Hemisphere cannot be determined basis due pronounced dynamic variability study clearly shows necessity calculation photolysis rates models.