V. Ya. Galin

Combined chemistry-climate model of the atmosphere

A combined three-dimensional global model of the chemistry and dynamics of the lower and middle atmosphere (up to 90 km from the Earth’s surface) is described. With the use of this model within the AMIP2 (1979–1995) program, numerical calculations were performed with consideration for the interactive coupling between the ozone content, radiation heating, and atmospheric circulation. Comparisons were made between calculated and observed data on the ozone content and temperature. Heterogeneous processes on the surface of polar stratospheric clouds were shown to be important for a correct simulation of the spatial and temporal distribution of atmospheric ozone.

Simulation of the impact of thunderstorm activity on atmospheric gas composition

A chemistry-climate model of the lower and middle atmosphere has been used to estimate the sensitivity of the atmospheric gas composition to the rate of thunderstorm production of nitrogen oxides at upper tropospheric and lower stratospheric altitudes. The impact that nitrogen oxides produced by lightning have on the atmospheric gas composition is treated as a subgrid-scale process and included in the model parametrically. The natural uncertainty in the global production rate of nitrogen oxides in lightning flashes was specified within limits from 2 to 20 Tg N/year. Results of the model experiments have shown that, due to the variability of thunderstorm-produced nitrogen oxides, their concentration in the upper troposphere and lower stratosphere can vary by a factor of 2 or 3, which, given the influence of nitrogen oxides on ozone and other gases, creates the potential for a strong perturbation of the atmospheric gas composition and thermal regime. Model calculations have shown the strong sensitivity of ozone and the OH hydroxyl to the amount of lightning nitrogen oxides at different atmospheric altitudes. These calculations demonstrate the importance of nitrogen oxides of thunderstorm origin for the balance of atmospheric odd ozone and gases linked to it, such as ozone and hydroxyl radicals. Our results demonstrate that one important task is to raise the accuracy of estimates of the rate of nitrogen oxide production by lightning discharges and to use physical parametrizations that take into account the local lightning effects and feedbacks arising in this case rather than climatological data in models of the gas composition and general circulation of the atmosphere.

Simulation of the indirect impact that the 11-year solar cycle has on the gas composition of the atmosphere

An interactive three-dimensional chemistry-climate model combining models of the gas composition and general circulation of the lower and middle atmosphere is used to study the impact of changes in extra-atmospheric solar radiative fluxes induced by solar activity on the stratospheric heating and subsequent temperature and ozone variations in the stratosphere and troposphere. The results have shown that a change in the atmospheric radiative heating resulting from variations in solar activity has a direct effect on the temperature and circulation of the atmosphere. Atmospheric temperature variations affect the rates of temperature-dependent chemical reactions, and this is considered the first type of indirect impact of solar activity on the atmospheric gas composition. On the other hand, as a result of the variation in atmospheric heating, its circulation changes, thus affecting the transport of minor gases into the atmosphere. This effect is considered the second type of indirect impact of solar activity on atmospheric gases. The results of our calculations have shown that both types of indirect impact of the variation in solar activity on the atmospheric gas composition are comparable in order of magnitude to the direct impact of solar activity on atmospheric gases.

Modeling the variability of gas and aerosol components in the stratosphere of polar regions

A thermodynamics-microphysics model of the formation and evolution of stratospheric clouds is developed. This model was integrated into the global chemistry-climate model of the lower and middle atmosphere. Model experiments on the study of the evolution of the gas and aerosol compositions of the Arctic and Antarctic atmosphere were performed. The results of an investigation into the observed differences of changes in the contents of gaseous impurities and aerosol in polar regions showed that the presence of nitrification in the Antarctic and its absence in the Arctic are the main factors controlling distinctions between the formation of a full-value ozone hole in the Antarctic and only occasional “mini-holes” in the Arctic.

Influence of wave activity on the composition of the polar stratosphere

The planetary wave impact on the polar vortex stability, polar stratosphere temperature, and content of ozone and other gases was simulated with the global chemical–climatic model of the lower and middle atmosphere. It was found that the planetary waves propagating from the troposphere into the stratosphere differently affect the gas content of the Arctic and Antarctic stratosphere. In the Arctic region, the degree of wave activity critically affects the polar vortex formation, the appearance of polar stratospheric clouds, the halogen activation on their surface, and ozone anomaly formation. Ozone anomalies in the Arctic region as a rule are not formed at high wave activity and can be registered at low activity. In the Antarctic Regions, wave activity affects the stability of polar vortex and the depth of ozone holes, which are formed at almost any wave activity, and the minimal ozone values depend on the strong or weak wave activity that is registered in specific years.

Analysis of the sensitivity of the composition and temperature of the stratosphere to the variability of spectral solar radiation fluxes induced by the 11-year cycle of solar activity

The sensitivity of the gas composition of the atmosphere and its temperature to the changes in spectral radiation fluxes during the 11-year cycle of solar activity has been analyzed with a chemistry-climate model of the lower and middle atmosphere. For this, the data of satellite measurements acquired in the first decade of the 21st century were used. The results of the model calculations showed that, in addition to the increase in the spectral flux in the absorption bands of molecular oxygen that leads to the growth of the ozone content, the changes in the flux at longer wavelengths are significant for the composition and temperature of the atmosphere. The changes of the ozone destruction rate in different catalytic cycles partly compensate each other; in these processes, the destruction rate increases in the reaction with atomic oxygen, while it decreases in the hydrogen and chlorine cycles.

Simulating indirect effects that thunderstorm activity has on atmospheric temperature

A coupled chemistry-climate model of both lower and middle atmospheres is used to study variations in the temperature of the atmosphere when its chemical composition is disturbed due to thunderstorm activity, which results in variations in its local heating and cooling and in atmospheric heat and mass transfer. The results of model calculations showed that, due to variations in the lightning production of nitrogen oxides and resulting variations in the concentrations of atmospheric gases, the temperature varies mostly in the lower and middle stratospheres over both tropical and polar regions. On average, over a period of several decades, this effect quantitatively amounts to a few tenths of a degree; however, it can reach a few degrees at heights of the lower stratosphere over Polar regions. The level of the statistical significance of estimates exceeds 0.95 almost within all height ranges for the global lightning production (exceeding 6 TgN/year).

Prognostic Estimations of the Atmospheric Ozone Content in the First Half of the 21st Century

New prognostic estimates are obtained for the potential variability of the atmospheric ozone content in the first half of the 21st century. The calculations are based on models of gas composition and general circulation in the lower and middle atmosphere and on the scenarios of the World Meteorological Organization (WMO). It is shown that the rate of ozone content increase will be controlled to a considerable extent by variations in stratospheric temperature. Even though the contents of atmospheric chlorine and bromine are not reduced, contrary to the WMO prediction, and remain at the present-day levels, the continuation of stratospheric cooling will lead to a rapid recovery of the ozone content to its level characteristic of the 1980s. Model experiments on variations in the stratospheric aerosol content have shown that an increase in the aerosol concentration will not affect the rate of ozone recovery in the atmosphere during reduced emissions of chlorine and bromine gases if the stratospheric temperature remains lowered. Numerical experiments have also shown that the simultaneous anthropogenic action on the contents of halogen gases and on the lower-stratosphere temperature can reduce the adverse effects of Freons and halons on the ozone layer.

Simulation of modern climate with the new version of the INM RAS climate model

The INMCM5.0 numerical model of the Earth’s climate system is presented, which is an evolution from the previous version, INMCM4.0. A higher vertical resolution for the stratosphere is applied in the atmospheric block. Also, we raised the upper boundary of the calculating area, added the aerosol block, modified parameterization of clouds and condensation, and increased the horizontal resolution in the ocean block. The program implementation of the model was also updated. We consider the simulation of the current climate using the new version of the model. Attention is focused on reducing systematic errors as compared to the previous version, reproducing phenomena that could not be simulated correctly in the previous version, and modeling the problems that remain unresolved.

Long-Term Variability of UV Irradiance in the Moscow Region according to Measurement and Modeling Data

We have found distinct long-period changes in erythemal UV radiation (Qer) characterized by a pronounced decrease at the end of the 1970s and a statistically significant positive trend of more than 5%/10 years since 1979 over the territory of the Moscow region according to the measurements and reconstruction model. The positive Qer trend is shown to be associated mainly with a decrease in the effective cloud amount and total ozone content (TOC). Due to these variations, UV resources have significantly changed in spring for the population with the most vulnerable skin type I, which means a transition from the UV optimum to UV moderate excess conditions. The simulation experiments using the INM-RSHU chemistry climate model (CCM) for several scenarios with and without anthropogenic factors have revealed that the variations in the anthropogenic emissions of halogens have the most significant impact on the variability of TOC and Qer. Among natural factors, noticeable effects are observed due to volcanic aerosol. The calculations of the cloud transmittance of Qer are generally consistent with the measurements; however, they do not reproduce the observed value of the positive trend.