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The current state of studies on short-lived atmospheric constituents (greenhouse gases and aerosols) is reviewed. They have short atmospheric lifetimes (from several days to a few years) and can significantly affect the environment and climate. We propose reducing the emissions of these constituents as an alternative to the reduction of man-made carbon dioxide releases. We consider methane, hydrofluorocarbons, tropospheric ozone, and various aerosols (primarily, black carbon); discuss their atmospheric sources and destruction mechanisms; evaluate their content, atmospheric emissions, and climate impacts; and recommend efficient actions for the nearest future.

Radiative forcing, the global warming potential, and the recently proposed global temperature potential are widely used not only in scientific studies but also in a number of economic and political evaluations of the effects of an increase in the contents of greenhouse gases and aerosols and other factors that form climate and its changes. New indices have appeared, and, to calculate them, information is required on the quantitative characteristics of the climate system’s components—current and expected—within standard periods of 20, 100, and 500 years. The calculations of some of these indices and potentials require consideration for variations in the rate of energy exchange between the atmosphere and the underlying surface (ocean) within the indicated periods. This leads to a more general problem of analyzing the sensitivity of the climate system to external (radiative) forcing and its response to such a forcing for the conditions of both stationary (equilibrium) and nonstationary “greenhouse” climates. A brief review of the few existing studies of such a response is given.

The solar climate ozone links (SOCOL) three-dimensional chemistry-climate model is used to estimate changes in the ozone and atmospheric dynamics over the 21st century. With this model, four numerical time-slice experiments were conducted for 1980, 2000, 2050, and 2100 conditions. Boundary conditions for sea-surface temperatures, sea-ice parameters, and concentrations of greenhouse and ozone-depleting gases were set following the IPCC A1B scenario and the WMO A1 scenario. From the model results, a statistically significant cooling of the model stratosphere was obtained to be 4–5 K for 2000–2050 and 3–5 K for 2050–2100. The temperature of the lower atmosphere increases by 2–3 K over the 21st century. Tropospheric heating significantly enhances the activity of planetary-scale waves at the tropopause. As a result, the Eliassen-Palm flux divergence considerable increases in the middle and upper stratosphere. The intensity of zonal circulation decreases and the meridional residual circulation increases, especially in the winter-spring period of each hemisphere. These dynamic changes, along with a decrease in the concentrations of ozone-depleting gases, result in a faster growth of O3 outside the tropics. For example, by 2050, the total ozone in the middle and high latitudes approaches its model level of 1980 and the ozone hole in Antarctica fills up. The superrecovery of the model ozone layer in the middle and high latitudes of both hemispheres occurs in 2100. The tropical ozone layer recovers far less slowly, reaching a 1980 level only by 2100.

We considered different properties of stratospheric sulfate aerosols and their size distributions and estimated how efficient they are at compensating for the changes in radiative fluxes at different atmospheric levels and deviation of air temperature during greenhouse warming and upon aerosol dimming. A two-dimensional zonally averaged model of the annually average radiative and thermal regime of the troposphere and stratosphere (the Energy Balance Radiative Convective Model, EBRCM) is used for this. This model allows for assessing the direct effects of changes in many parameters of atmospheric aerosols and the underlying surface, as well as characteristics of aerosol screens. We estimate the sulfate aerosol optical depths and masses for offsetting the annually and zonally averaged increases in the near-ground air temperature, caused by increases in the greenhouse gas content, according to measurements and the IPCC A2 scenario for 1970–2050. No offset is indicated if aerosol screens are emplaced in the polar zones (poleward of 70° N–70° S), and a screen emplaced in just one hemisphere is shown to be incapable of producing total offsetting of global warming.

In accordance with numerous investigations, global climate warming due to the increased greenhouse gas content in the atmosphere can significantly influence the environment already in the near decades. In order to mitigate or prevent possible adverse consequences of this warming the technologies on reducing greenhouse gas emissions as well as a deliberate interference with climate, including its control, are under consideration. Let us analyze the present investigations on the estimate of the influence of a simultaneous increase in the atmospheric CO2 concentration and in the stratospheric aerosol on the global and regional climate, ozone layer, and World Ocean acidification. It is noted that the production and subsequent maintenance of the artificial aerosol layer in the stratosphere could, in principle, eliminate or retard climate warming, but it would be accompanied by a decrease in the global precipitation, especially in the tropical zone. Furthermore, the stratospheric aerosol screen does not solve the problem of the atmospheric CO2 increase, which in turn results in the further World Ocean acidification, and thus has an adverse effect on the marine part of the biosphere. Political and ethic issues connected with the deliberate global man interference with the natural environment are also under considerations.

A one-dimensional ionic-photochemical model of the gaseous composition of the atmosphere that describes the formation of the D layer of the ionosphere is presented. Based on this model, the vertical profiles of the concentration of electrons and ions in the D layer of the ionosphere were calculated, as were the vertical distributions of minor gaseous constituents in the atmosphere up to a height of 86 km for undisturbed conditions and after a powerful solar proton events (SPE) at the end of October 2003. The calculations showed that SPEs significantly increase NOx in the mesosphere of polar latitudes. In the lower mesosphere of polar caps, the NOx mixing ratio increases by 20–50 ppb; in the upper mesosphere it increases by 100 ppb and more. High NOx levels in zones of their formation can be retained for several weeks, producing a long-term but comparatively small ozone decrease in the lower mesosphere. The main ozone decrease is caused by a short-term HOx increase after SPEs and is also of a short-term character in the conditions of the illuminated mesosphere. After the SPE in October 2003, model calculations yield an ozone concentration decrease by 40% in the middle and upper mesosphere at 75 ° S and by 70% at the same heights at 70 ° N. The results of modeling NOx and O3 changes after the SPE in October 2003 agree well with the data of satellite measurements. The changes in minor gases of the mesosphere after the SPE obtained in the model with parameterized sources of HOx and NOx are compared with their changes obtained in the complete ionic-photochemical model. The changes in HOx, NOx, and O3 coincide rather well, whereas the changes in ClO noticeably differ, especially in the lower mesosphere. Thus, at a height of about 60 km, the parameterized photochemical model underestimated twofold the ClO formation after the SPE.

Methane emitted into the atmosphere from sources located in the Urengoi natural gas field is estimated from direct methane concentration measurements in the atmospheric boundary layer and modeling. The results of direct profile measurements in the summer-fall season of 2003 are generalized versus the data from the previous field studies and background monitoring of greenhouse gases in the northern polar region. The use of models for calculating the intensity of emission from sources located in the field area together with a set of methane concentration measurements at three altitudes allowed the authors to develop a method of verification of emission from a specific source, a deposit. The method estimates the emission both from part of the field area and from the whole field with an irregular distribution of the intensity of sources across the deposit area.

Synoptic analysis of monthly and daily mean total ozone fields is carried out using ground-based (Roshydromet) and TOMS measurements. Large interannual changes in the evolution of the stratospheric polar vortex and the North Pacific anticyclone influence the formation and dynamics of the winter-spring ozone fields in the stratosphere of high northern latitudes. The analysis shows considerable variations in the direction of zonal ozone transport from the sector of ozone inflow from low latitudes and accumulation in the Far East depending on the winter polar stratosphere temperature and the quasi-biennial oscillation (QBO) phase. In years with the easterly QBO phase and the warm polar stratosphere, ozone at the end of winter is transported to northeastern Canada and Atlantic. In years with the easterly phase and cold polar stratosphere, ozone transport is directed to northern Eurasia. These characteristics will be verified on extensive observational data.

This is a study of the sensitivity of model results (atmospheric content of main gas constituents and radiative characteristics of the atmosphere) to errors in emissions of a number of atmospheric gaseous pollutants. Groups of the model variables most dependent on these errors are selected. Two variants of emissions are considered: one without their evolution and the other with their variation according to the IPCC scenario. The estimates are made on the basis of standard statistical methods for the results obtained with the detailed onedimensional radiative—photochemical model of the Main Geophysical Observatory (MGO). Some approaches to such estimations with models of higher complexity and to the solution of the inverse problem (i.e., the estimation of the necessary accuracy of external model parameters for obtaining the given accuracy of model results) are outlined.

ISSN 1028-334X, Doklady Earth Sciences, 2006, Vol. 408, No. 4, pp. 595–598. © Pleiades Publishing, Inc., 2006.Original Russian Text © V.A. Zubov, E.V. Rozanov, A.V. Shirochkov, L.N. Makarova, T.A. Egorova, A.A. Kiselev, Yu.E. Ozolin, I.L. Karol, W.K. Schmutz, 2006, published inDoklady Akademii Nauk, 2006, Vol. 408, No. 2, pp. 243–246.

Major processes of generation of the methane field in the atmosphere over northwestern Russia have been studied on the basis of measured surface concentration and total content of methane in the environs of St. Petersburg, air-mass trajectories, and a three-dimensional regional pollution transport model. It is shown that the contribution of methane emission from an industrial center to the total column amount of methane is no more than 2% of its average value. At the same time, because of this emission, the surface methane concentration in the environs of St. Petersburg varies by as much as 50%. The origin of air masses arriving at the site of measurements influences both the total content and the surface concentration of methane. The air masses that passed over the continental part of western and eastern Europe are characterized by the values of total content and surface concentration of methane that are about 4% higher than those in the air masses formed over the ocean, which come to the region from the northwest. The regional transport model for greenhouse gases satisfactorily describes the results of surface measurements and adequately simulates observed tendencies in the change of total methane content. An estimate of the integral emission of methane into the atmosphere from St. Petersburg and its industrial suburbs is about 100 kt per year.

This review is devoted to problems in the photochemical modeling of atmospheric processes. The physicochemical and mathematical foundations underlying the construction of photochemical models are described, a classification of the atmospheric reactions is presented, and the features of photochemical modeling are considered under various irradiance conditions for various atmospheric layers and geographical regions. Atmospheric processes that are important to photochemical models are discussed. Applications involving photochemical models are outlined. Some results are presented to illustrate the capabilities of photochemical models. Special attention is given to relatively recent directions in photochemical modeling, such as data assimilation and inverse problems. The review can be used by experts in areas related to atmospheric chemistry as a basic source of knowledge on the subject and for the development of photochemical modules for atmospheric models.

A chemistry climate model is used to evaluate of the possible influence of Joule heating induced by the solar wind and interplanetary magnetic field (IMF) elements on the ozone concentration and dynamics of the Earth atmosphere. The Joule heating rates in the stratosphere are parameterized on the base of the time series of the solar wind and IMF parameters taken from the NASA database (Interplanetary Medium Data Book, NASA, USA, 1999) for 1996. The results of the 10-year-long model run with the additional Joule source of heat are compared with the output of the unperturbed (control) 20-year-long model run. Both simulations are performed in equilibrium mode with prescribed boundary conditions and for the minimum of the 11-year solar cycle. The comparison of the model outputs shows that the simulated atmosphere is rather sensitive to the introduced Joule heating. The most significant changes were found in the lower stratosphere of the northern hemisphere (NH). The NH lower-stratospheric temperature increases by 1–3 K almost throughout the whole year with the significance level at 95% or higher. In boreal summer, the changes of the ozone concentration are anti-correlated with the temperature as expected from the gas phase photochemical theory. In boreal autumn and spring, the variations of the ozone mixing ratio can be affected not only by the local temperature changes but also by the redistribution of the meridional circulation in the stratosphere. In the southern hemisphere (SH), the additional Joule heating leads to a significant increase of the stratospheric temperature for the austral winter ( ∼ 2 K ) . The most substantial SH ozone changes ( ∼ 10 % ) are found in the lower stratosphere during the austral spring.

The Main Geophysical Observatory 2D channel photochemical model is used to study the behavior of tropospheric OH within the 30–60°N zonal belt in relation to changing NOX and CO emissions. The changes of tropospheric OH as a function of the contributions by NOX and CO emissions during the period 1850–2050 are calculated. Our estimations show that the largest annual increment of total tropospheric OH within the belt considered occurs in the 1985–1995 period, about 0.27% yr −1 . Based on scenarios of tropospheric pollution emissions in the first half of 21st century, the total tropospheric OH content will increase more slowly, by 0.12– 0.15% yr −1 . The maximum growth of OH concentration occurs close to air pollution locations—in the lower troposphere during 1850–1995 but in the upper troposphere in the 21st century when the NOX source from subsonic aircraft increases faster than the surface source.

In the paper of A.G. Ryaboshapko [5], unfortunately, the author evaded the main question contained in the name of the paper criticized by him [4], namely, “Is Aerosol Scattering in the Stratosphere a Safety Technology Preventing Global Warming?” Instead of this, having named his paper “On the Taboo on Researching in the Field of Global Climate Geoengineering,” he discussed a completely different question which was not formulated by the authors. A thesis on “the taboo on researching” disputed by the author of the critical paper and the doubtfulness (from the point of view of the Russian science priorities) of some researches 1 discussed by us is far from being the same. In other words, not the actual position is under critique but that ascribed to the authors. Reverting to the discussion opened in [4], let us first of all specify its topic. A term “geoengineering” which came to us from the English-language literature embraces a wide range of various techniques of climate warming prevention. In order to preclude a potential confusion, in the report [7], for example, it is proposed to divide all kinds of climate regulation into two classes: techniques directed at the direct removal of CO2 from the atmosphere and techniques of the solar radiation control for the purpose of decreasing its absorption by the Earth’s surface. Recent investigations demonstrated that the use of technique of the second class is able to bring a large-scale damage to the environment and economic development of certain regions of the globe. These are the deliberate aerosol scattering in the stratosphere to control the solar radiation coming to the Earth’s surface and problems associated with this technique were discussed in our paper. Thus, the author of [5] substitutes the discussion of stratospheric aerosol scattering by the discussion of the great variety of techniques embraced usually by the general term “geoengineering” which we did not deal with. By the way, the authors avoided this term in [4] concentrating on the concrete technique.

Ozone depletion is a major global scientific and environmental problem. One of its causes is the anthropogenic increase of CFCs in the atmosphere, which results in the enhancement of the concentration of reactive chlorine in the stratosphere. To reduce the influence of anthropogenic ozone-depleting substances, the Montreal Protocol was agreed by Governments in 1987, with several Amendments adopted later. What has been the result of the Montreal Protocol and its Amendments (MPA)? Here we present the first 3D-model assessment of the effect of the MPA on atmospheric ozone which has been performed with the University of Illinois at Urbana-Champaign (UIUC) Atmospheric Chemical Transport Model (ACTM). We find that the MPA has saved up to 2% of the present-day total ozone in the Northern Hemisphere and about 5% in the Southern Hemisphere. Our calculations also show that CFCs do not play the major role in the observed recent total ozone variations.

The West Siberian region is one of the main contributors of theatmospheric greenhouse gas methane due to the large areas ofwetlands, rivers, lakes and numerous gas deposits situated there.But there are no reliable estimations of integral methane flux fromthis area into the atmosphere. For assessment of methane fluxes inWest Siberia the specially constructed 3-D regional chemicaltransport model was applied. The 3-D distribution of methane iscalculated on the basis of the current meteorological data fields(wind, temperature, geopotential) updated 4 times a day. The methaneconcentrations measured near the main gas fields of West Siberia inthe summer season of 1999, were used for correction of methane fluxintensity estimates obtained previously by comparison ofmeasurements carried out in summer 1993 and 1996 with modelledmethane mixing ratio distribution. This set of field and modelexperiments confirmed the preliminary conclusion about low leakageintensity: anthropogenic methane flux does not exceed 5–15% oftotal summer methane flux, estimated as 11–12 Mt CH4 in summer from this region, in spite of the large areas of gas deposits located there.

The effect of NO x and CO pollution on other important atmospheric gases from 0–16 km in the northern temperate zonal belt is calculated using a 2-D (altitude–longitude) channel photochemical model with climatic zonal and vertical fixed transport. The geographical inhomogeneities of the NO x and CO large-scale surface releases are modeled. The distinction between NO x and CO fluxes from the oceanic and land surfaces and those from areas with various pollution source intensities is considered. NO x and CO emissions from world transport aviation engine exhausts and the NO source from lightning discharges are also included. Model results are analyzed and compared with observational data for nitrogen compounds, carbon monoxide, and ozone. The dependence of the spatial and temporal hydroxyl distribution on the carbon monoxide (as the main destroyer of OH) concentration field is analyzed and discussed.

A concept of the PTI is proposed to characterize the photochemical interactions of aircraft exhausts with the ambient air. The PTI is the ratio of NOx, CO,, ozone, and NOy transformed in the plume during its lifetime period tp to NOx and CO released into the plume initially. An estimate of tp is calculated by prescribing the 10% excess of emitted (NOx)p in the plume over the (NOx)a of the ambient air at the end of plume life. Simple analytical formulas for PTI are obtained from the known plume box model. The tp, PTI of NOx, HNO3 and O3 are calculated and analyzed for different moments of releases during the daytime in and out of flight corridor. The in-plume NOx conversion to HNO3 and O3 enhancement are found to be the largest in daytime, in July and in the lower stratosphere.

The MGO 2D (altitude–longitude) channel photochemical transport model has been applied to elucidate the spatial and temporal behavior of the hydroxyl radical in the troposphere of the northern temperate belt for the pre-industrial (1850) period and the last few decades (1960 and 1995). The relation between the tropospheric OH content and the carbon monoxide, methane, nitrogen oxides emissions during 1850–1995 is studied. The distribution of the carbon monoxide concentration is calculated and validated using the observational data collected in the different locations because of the geographical non-homogeneity of its emissions. The response of the hydroxyl radical concentrations to the non-homogeneity of the CO and other atmospheric species distribution is estimated. The carbon monoxide and methane contributions to the hydroxyl photochemical sink are also evaluated. Because the changes of OH in the troposphere alternate the intensity of methane and carbon monoxide oxidation, the CO, CH4 and OH lifetime evolution due to the increase of anthropogenic pollution intensity is analyzed and discussed.

Recent measurements of CO2, CH4, and N2O content in Antarctic and Greenland ice core air allow the use of an one-dimensional radiative-photochemical model to reconstruct the annual global mean vertical distributions of trace gas concentrations for four periods: the contemporary period of 1985, the preindustrial period of 1850, the last glacial period of 18 ka B. P., and the interglacial period before the latter of 120–130 ka B. P. In this model reconstruction, the changes in surface air temperature and tropospheric relative humidity are prescribed, and both dry adiabatic and moist adiabatic lapse rates are used together with several other external estimates of radiative and photochemical parameters for these periods. The considerable reduction of greenhouse gas content in the atmosphere of both glacial and interglacial periods, including about a 50% reduction of stratospheric moisture in the glacial, leads to the warming of the middle and upper stratosphere by about 11 K and 4 K, in the glacial and interglacial periods, respectively. Stratospheric composition is found to be little sensitive to possible large variations of CO and NOx surface sources. The ozone mixing ratio drops to 10–12 ppbv in the lower troposphere and increases to a maximum 6.0–7.5 ppmv in 40 to 46-km layer, but remains almost the same as in preindustrial and in 1985 periods in the 20 to 30-km layer. This results in the approximate conservation of total ozone for all four periods considered.

The chemistry-climate model (CCM) SOCOL has been used to evaluate the contribution 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 atmospheric concentration of the greenhouse gases (GHG), ozone depleting substances (ODS) and sea surface temperature and sea ice (SST/SI) distribution. The last one 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 with CCM SOCOL for the years 2000, 2050, and 2100 taking into account all factors separately and all together. It was established that 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 very important role in the evolution of ozone atmospheric content 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 velocity and the meridional circulation intensity 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 simulated results 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.

Following numerous model studies of the global impacts of sub- and supersonic aircraft on the atmosphere, this paper assesses the separate aircraft engine exhaust effects of the 45°N cruise flight and at the 10- and 18-km levels of the July atmosphere. A box diffusion photochemical model in the cross-section plane of the flight trajectory is used to compute the effects of gas-phase and heterogeneous reactions on the condensation trail particles in the troposphere, and on the sulphate aerosols in the stratosphere. The enhanced horizontal dispersion of the exhaust plume is considered in the model. A significant but short term depletion of ozone is predicted, which is 99% restored in about 1 h in the wide plume with enhanced horizontal dispersion, but requires more than 24 h in the narrow plume without it. The oxidation rate of NO and NO2 into the HNO3 depends on the OH content in the exhausts and varies in all the cases. The heterogeneous photochemistry has only a small influence on the initial evolution of N2O5 and HO2 in the plume.

The Cause-and-Effect Analysis (CEA) technique is used to estimate changes in the equilibrium of a simplified system of interactions for global tropospheric methane due to changes in external forcing. This system consists of methane, carbon monoxide, tropospheric ozone, stratospheric ozone, total ozone, hydroxyl, water vapor and temperature. The CEA technique allows determination of all the loops in the system and the all pathways from the system's external parameters to all variables of the system. The values of the system's links are estimated for annually averaged conditions. It is found that the value of the net loop effect of the system, D, which is a measure of the system's sensitivity to changes in the external forcing, is less than unity and depends predominately on the interactions between temperature and water vapor, and on the links that define the influences of methane and carbon monoxide on hydroxyl. The anthropogenic sources of methane and carbon dioxide are considered as the external forcing to the system. It is shown how the system generates: (1) negative sensitivities of tropospheric methane and carbon monoxide to an increase in carbon dioxide and a positive sensitivity to an increase in the anthropogenic methane source, (2) negative sensitivity of tropospheric ozone to an increase in the carbon dioxide and a positive sensitivity to an increase in the anthropogenic methane source, and (3) negative sensitivity of hydroxyl to an increase in the anthropogenic methane source.

The radiative-photochemical modelling of the global composition changes under the radiative-active gas releases is performed according to the known IPCC scenarios up to year 2100, with inclusion of time delay of greenhouse troposphere warming due to oceanic thermal inertia. The corresponding tropospheric humidity increase provided by the usual condition of relative humidity conservation in the troposphere is accounted also. The enhanced methane release in “business as usual” A scenario may lead to lessening of the ozone depletion in the troposphere and stratosphere in the 21st century. For scenario B of partly controlled radiative-active gas emissions the “business as usual” methane release causes a significant drop of OH content in the greenhouse warmed and humid troposphere. The oceanic delay in tropospheric warming has a limited influence on the rate of tropospheric composition change. The enhanced chlorofluorocarbons releases in A and B scenarios lead to significant ozone content decrease in the lower stratosphere caused by Cl and Br radicals and to the total ozone depletion amounting to 15% to the end of the century.

[1] This paper is intended to investigate the statistical significance of the ozone recovery amounts computed with the chemical transport model (CTM) MEZON, given errors in the reaction rates and model initial conditions. The CTM is used to investigate the sensitivity of the ozone to Montreal Protocol and its Amendments (MPA) restrictions on the emission of ozone depleting substances in the atmosphere during 1992–2002. The known Student's t-test is applied for the assessment of the statistical significance of the “saved” total ozone (TO) by the MPA. The results reveal that the uncertainties in the initial fields do not substantially reduce the statistical significance of the results. Substantial reduction of the statistical significance is caused by the uncertainty in the kinetic constants. The model noise level reaches its highest values (up to 10%) in the polar areas during late winter - early spring. The “saved” TO also reaches its maximum there and, therefore, it is significant at the 90–95% confidence level.

Methane coming into the atmosphere from natural and anthropogenic sources plays the important role in greenhouse warming. Atmospheric methane content is increasing by ~ 0.6-0.8 % per year, especially in high and temperate latitudes of Northern Hemisphere. Therefore the quantitative study of injection and destruction mechanisms of atmospheric methane is important for estimation of observed climate changes. The wetlands in common with the large oil- and gas deposits located in Siberia and in Russian Arctic are among the main methane sources in the Northern Hemisphere. The measurements of methane concentrations carried out in the vicinity of gas fields in spring of 2000 in common with specially developed for this region 3-D regional transport model are used for correction of estimates describing the methane leakage from gas deposits. The obtained results allow to make more accurate assessment of the regional sources input into the natural and anthropogenic components of global atmospheric methane budget.

Many theoretical studies testify to an exceptionally important role of OH radical in the tropospheric chemistry (Crutzen, Zimmermann, 1991; WMO/UNEP, 1999; etc.). Due to its extremely high reactivity, OH controls or essentially influences the content of many tropospheric species, such as carbon monoxide CO, methane CH4, ozone O3, nitrogen oxides and others. Simultaneously, these species determine the behavior of tropospheric OH. As a result of their chemical interactions, the quantitative estimations of tropospheric hydroxyl concentration were calculated by the models of different complexity (e.g. Lelieveld et al., 1998; Wang, Jacob, 1998; Kiselev, Karol, 1999, 2000a). But it is difficult to validate them by the relevant observations, as there is presently no instrumentation for regional to global scale those of tropospheric OH (Brasseur, Prinn, 2000). Thus, the regular monitoring of tropospheric OH is not yet established and there are a few its isolated measurements only (e.g. Kleinman et al., 1998; Brune et al., 1999). Under the circumstances modeling is a basic tool of study of tropospheric OH chemistry. Up to now there is no common opinion among the specialists about the evolution of tropospheric OH, and the modern model reconstructions of its trend differ not only in magnitude but in sign. According to Martinerie et al. (1995), Kiselev, Karol (2000a) the tropospheric OH content has been increasing last 150 years but other studies (e.g. Lelieveld et al. (1998), Chappellaz et al. (1993)) evaluate the drop of tropospheric OH in the same period.

A concept of Effective Emission Indices (EEI) was introduced by several authors to assess the effects of photochemical processes in the exhaust plume on the exhaust product global inventory. We divide EEI in two factors: EEI = EI × PTI, where the known Emission Index (EI) quantifies the in-engine processes and dimensionless Plume Transformation Index (PTI) is the ratio of the NOX, NOY components, O3 or CO molecules transformed in the plume during its lifetime period to the initially emitted NOX or CO molecules into the plume. The plume lifetime period is limited by setting the prescribed small excess (10%) of emitted (NOX)P in the plume over the (NOX)a of the ambient air. EI is estimated for the most of currently used aircraft engines (IPCC, 1999). PTI was calculated by Meijer et al. (1997) and Karol et al. (1999) using the plume photochemical model for various ambient conditions.

The Global Warming Potential (GWP) and Radiative Forcing (RF) are widely used for the evaluation a separate Radiative Active Substance (RAS) effects on the climatic regime of the atmosphere. In a radiative photochemical model, calculations of RF of the chemically active Greenhouse Gases (GG) caused by gas content change is proposed in two ways: by the Cumulative (CS) and Individual (IS) schemes. The Global Warming Commitment (GWC) is calculated by the same formula as GWP, but considering actual RAS emission and RAS content changes in certain periods. GWC specifies the RF of RAS by taking into account not only the initial and final RAS concentration distribution as RF does, but also the concentration evolution during the period. All these indices are calculated and analysed for periods: 1850–1995 and 1995–2050 for two IPCC IS92 scenarios.

A box and a Gaussian plume model including gas-phase photochemistry and with plume dispersion parameters estimated from the few available plume observations are proposed and used for evaluation of photochemical transformations of exhausts from a single subsonic transport aircraft. The effects of concentration inhomogeneities in the plume cross section on the photochemical sources and sinks in the plume are analyzed for various groups of compounds. The influence of these inhomogeneities on the rate and on the mass of ambient air entrainment into the plume are studied also by comparing the box and the Gaussian plume model simulations during the first hours of their "life''. Due to the enterance of HOx and NOx from ambient air into the plume with rates varying from the wind shear and turbulence conditions, the rate of emitted NOx oxidation in the plume is dependent on these and also on the background concentration levels of HOx and NOx.

Main components of the methane atmospheric cycle are outlined and contemporary understanding of their input in the global change is reviewed. Special attention is paid to methane atmospheric content increase influence on atmospheric composition and on the expected climate changes. The connections of the latter with methane source and sink intensities is also discussed.

In this chapter, we consider a change in anthropogenic methane sources to be the external forcing for the global atmosphere. The global atmosphere is represented simply by a linearized system of interactions near their equilibrium values of annually averaged temperature and methane, carbon monoxide, tropospheric ozone, stratospheric ozone, total ozone, hydroxyl, and water vapor.

Linear trend analysis of geophysical time series is considered in connection with the problem of determining long-period variations (possibly of man-made origin) in the presence of short period noise of larger amplitude. Criteria for testing hypotheses about linear trends are presented for the cases of independent observations and of the observations whose correlation function is known. The possibility of increasing the precision of the results using area-averaged values is investigated. Examples are given of the long time series analysis of air temperature, carbon dioxide and water vapor content. Time series of total atmospheric ozone content at some stations are also considered, and conditions for correct statistical analysis of such data are given.

A scheme of a system of physical and chemical processes controlling the production, transport and destruction of ozone and its gaseous catalysts, as well as other related gases in the low and high stratosphere is presented. An account is made of temperature variations of the stratospheric layer resulting from changes in ozone content; also included is the effect of temperature variations on photochemical reaction rates and ozone and other gases transport between atmospheric layers. Parameters describing major relations of the system are inferred from the analysis of ozone and trace gas data and from the results of model calculations of interdependence between variations in temperature and ozone content of the layer.

The temporal change of the zonally averaged monthly mean aerosol concentration in the atmospheric layer up to 25 km is calculated for the instantaneous sources in the lower stratosphere by means of numerical calculation of boundary problems for the two-dimensional macroturbulent diffusion equation; the mean meridional circulation is taken into account. The coefficients of these problems are determined partly from climatic temperature and wind data and partly from comparison of calculations with published data on the global content of some radioactive isotopes produced in nuclear explosions. Results of calculations demonstrate the essential contribution that meridional circulation makes to the seasonal changes of and meridional distributions of zonally averaged isotope fallout π and surface air concentration cs and the contribution of this circulation to isotope transport across the equator and through the tropopause. The moment of injection has only a slight influence on the seasonal change of π and cs in the second calendar year of isotope spreading. Meridional distributions of π and cs are almost independent of the source latitude by 6 months after injection in the hemisphere of injection and by 12–15 months in the other hemisphere.

A model of tracer transport process in the meridional plane of lower stratosphere is briefly outlined and the corresponding partial differential equation for tracer concentration is deduced. For the long lived radon daughters RaD(Pb 210 ) and RaF(Po 210 ) in the Northern Hemisphere stratosphere such equations can be simplified to one dimensional stationary form, describing the quasivertical transport of these isotopes. The mean values of quasivertical velocity and turbulent diffusion coefficient in the lower stratosphere of different latitudes of Northern Hemisphere are estimated by comparison of last equation solutions with the published results of aircraft measurements of RaD and RaF concentration in 1961 and 1962. These estimated values agree with the known qualitative ideas on latitudinal and seasonal changes of the stratospheric mixing intensity. DOI: 10.1111/j.2153-3490.1966.tb00245.x

A 3D mesoscale tropospheric photochemical transport model of high spatial resolution has been developed and used for assessment of the methane concentrations and methane emission in the West Siberian region of intensive mining of natural gas and oil deposits. The model is validated against the measurements of methane concentration at the surface and in the lower troposphere collected during July 1993 and June 1996 experiments. Comparison of the simulated and observed concentrations allowed to estimate that during the above periods the average natural methane fluxes were as high as 65 mg m −2 day −1 . The anthropogenic methane fluxes (leakage from gas deposits) integrated over model domain during the same time period were about 20% of the total methane emission from relevant areas.

The data on the chemical composition of precipitation obtained during the period from 1958 through 1965 at 28 stations situated on the European Territory of the USSR (ETU) are used to calculate correlation functions of Ca?, Na., SO? 4 ion and ion sum concentrations in precipitation and deposition. Correlation distances for various ions are found to be in the range of 90 to 450 km. The mean square random errors in ion composition measurements (35–45%) are estimated using calculated correlation functions. It is shown that the mean station separation of about 100 km gives the error of optimum interpolation to the point for the total ion concentration in precipitation equal to the random error of observations. The optimum averaging of the deposition value over some area can give the same error, 2–3 stations being in the square of 300 times 300 km 2 . DOI: 10.1111/j.2153-3490.1972.tb01569.x

The boundary value problem for the differential equation for mean zonally averaged tracer concentrations in the meridional plane up to 25 km level and from pole to pole is introduced and connected with a model of tracer transport processes in the atmosphere on a global scale. The coefficients of this equation are determined from climatic data on the mean meridional circulation and macroturbulent diffusion. The finite difference analogue of this problem is solved numerically by the method of matrix factorisation, and the annual mean zonally averaged concentration distributions for Rn 222 , Pb 210 , and Po 210 are obtained for several variants of parameters. The results of the calculation are compared with the published data of isotope concentration measurements in the free atmosphere, and the global intensity of macroturbulent diffusion is estimated. The calculated isotope content in the troposphere and stratosphere of the northern and southern hemispheres and their rates of transport across the equator and through the topopause are briefly outlined. DOI: 10.1111/j.2153-3490.1970.tb01523.x