I. G. Dyominov

Greenhouse gases and future long-term changes in the stratospheric temperature and the ozone layer

A numerical two‐dimensional (2D) interactive dynamical–radiative–photochemical model including aerosol physics is used to examine the expected long‐term changes in stratospheric temperature and the Earths ozone layer due to anthropogenic pollution of the atmosphere by the greenhouse gases CO2, CH4 and N2O. The model time‐dependent runs were made for the period from 1975 to 2050. The results of the calculations show that the basic mechanism by which greenhouse gases influence the ozone layer is stratospheric cooling accompanied by a weakness in the efficiency of the catalytic cycles of ozone destruction due to temperature dependencies of the photochemical gas‐phase reactions. Modification of polar stratospheric clouds (PSCs) caused by anthropogenic growth of the greenhouse gases is important only for the polar ozone. An essential influence of the greenhouse gases on the ozone by a modification of the stratospheric sulphate aerosol is revealed. The aerosol changes caused by the greenhouse gases modify the distribution of the ozone‐active gaseous chlorine, bromine and nitrogen components by means of heterogeneous reactions on the aerosol surface, resulting in a significant decrease in springtime polar ozone depletion of the Antarctic ozone hole.

Contribution of solar UV radiation to the observed ozone variations during the 21st and 22nd solar cycles

A two-dimensional dynamical radiative-photochemical model of the ozonosphere including aerosol physics is used to examine the changes of the Earths ozone layer occurred during the 21st and 22nd solar cycles. The calculated global total ozone changes in the latitude range 60°S—60°N caused by 11-year variation of solar UV radiation, volcanic eruptions, and anthropogenic atmospheric pollution containing CO2, CH4, N2O and chlorine and bromine species are in a rather good agreement with the observed global ozone trend. The calculations show that the anthropogenic pollution of the atmosphere is a main reason of the ozone depletion observed during the last two solar cycles. However, the 11-year solar UV variation as well as volcanic eruptions of El Chichon and Mt. Pinatubo also gave a significant contribution to the observed global ozone changes.

Seasonal variations of water and odd nitrogen concentrations at stratopause altitudes

Abstract An attempt is made to determine seasonal variations of water vapour and odd nitrogen contents in the upper stratosphere by solving the inverse problem of the kinetics of ozone formation using available ozone sounding data. A numerical photochemical model of the upper stratosphere and mesosphere is used which takes into account oxygen, hydrogen and nitrogen constituents. It has been found that the volume mixing ratio of water vapour r H 2 O at the altitudes 40–50 km varies during a year from about 1 to 4 ppmv. The odd nitrogen volume mixing ratio r NO x varies from about 10 to 45 ppbv. The average values for r H 2 O and r NO x are about 2.6 ppmv and 31 ppbv, respectively. During the summer half of the year (approximately April–September), variations of water vapour and odd nitrogen contents are negligible, but during the winter period and at intermediate seasons great variations are observed for r H 2 O and r NO x . Thus the water vapour mixing ratio in November decreased by a factor of about three compared to October and then increased again in December by a factor of three and a half. A notable decrease in r H 2 O was observed in February–March. The maximum and minimum values of r NO x were exhibited also during the winter half of the year.

Study of Ozone and Temperature Variations in the Troposphere and Stratosphere Due to Anthropogenic Perturbations

Two-dimension model of the troposphere and stratosphere has been used for an estimation of ozone and temperature changes due to anthropogenic pollution of the atmosphere. It is shown that total ozone changes in December of 2050 at 45°N caused by anthropogenic discharges of CH4, N2O, and chlorine species are about 1.7%, −1.9% and −3.4%, consistently. Temperature increases near the Earth’s surface due to greenhouse effect are 0.21 K, 0.16 K and 0.36 K in these cases. Corresponding changes of the upper stratospheric temperature (0.8 K, −1.7 K and −3.8 K at 40 km) are caused mainly by ozone changes (3.1%, −4.8% and −10.4%). Simultaneous influence of the different anthropogenic species is non-additive and leads to less changes of both the ozone and the temperature of the atmosphere.