In the recent decade, IAP has been actively developing theoretical studies and modeling of different-scale spatio-temporal variability of minor gaseous atmosphere constituents. This variability is determined primarily by the photochemical reactions that run in the atmosphere, depends significantly on the different transport processes, and is an important source of information about the current status and evolution of the atmosphere. Analysis of these processes from the viewpoint of nonlinear dynamics and development of special basic dynamic models of atmospheric photochemical systems (PCSs) serve as the basis of the studies of photochemical processes in the Earth's atmosphere supervised by A. M. Feigin. Sets of such processes and their parameters are essentially different in different atmospheric regions. Therefore, one conventionally singles out PCSs of the boundary layer, free troposphere, polar lower stratosphere, mesosphere, etc.

Dynamics of the ozone density in the process of formation of the Antarctic ozone hole, which was calculated in the framework of the basic model (a) vs. observations (b, c)

IAP researchers have developed a basic photochemical model of the lower-stratosphere polar PCS which demonstrates good qualitative correspondence to the observed behavior of ozone density. Instability of the Antarctic PCS has been revealed: a self-oscillatory process has been detected in an atmospheric PCS for the first time. During the period of the ozone hole formation, the corresponding PCS undergoes a series of bifurcations, and further changes in the bifurcation characteristics due to the trends in control parameters (primarily, densities of inorganic chlorine and greenhouse gases, as well as temperature) influence significantly the process of the expected ozone hole recovery (A. M. Feigin, I. B. Konovalov).
The basic photochemical model of the mesospheric PCS has been developed; the chemical and nonlinear-dynamical mechanisms of the nonlinear response of the system to the diurnal variations of solar radiation (altitudes of 80—90 km) have been studied; the possibility of excitation of a new type of reaction-diffusion waves, which are fronts or phase pulses of nonlinear photochemical oscillations in the densities of minor gas constituents, which propagate in the Earth's atmosphere along the latitude circle, has been predicted theoretically; it has been shown that the subharmonic nonlinear response of the mesospheric PCS to diurnal variations of solar radiationcan be a reason of multiple amplification of quasi-two-days atmospheric waves observed in the mesosphere and lower thermosphere (A. M. Feigin, I. B. Konovalov, M. Yu. Kulikov).
A new method of determination of the atmosphere parameters basing on the results of observation of minor gas constituents has been developed on the basis of the concept of basic dynamic models. The method was used to process the satellite measurement data about vertical distributions of the temperature and the densities of ozone О3 and hydroxyl OH in the mesosphere and lower thermosphere of the Earth (altitudes from 50 to 90 km). It has been found that the nonuniformity of the vertical distribution of water increases by many times in the upper mesosphere, i.e., the region of formation of noctilucent clouds which are the highest clouds in the Earth's atmosphere (A. M. Feigin, M. Yu. Kulikov).

Spatio-temporal evolution of the density of atomic hydrogen at an altitude of 85 km. The front of the phase jump of the two-day oscillations propagate along the longitudinal circle with the constant velocity	Vertical distributions of the density of Н2О at 69—710 N, 60—650 W (bold solid line and dots) and 66—680 N, 141—1480 W (bold dashed line and hollow diamonds) found from the CRISTA-MAHRSI data. Thin solid and dashed lines show the retrieval error.

Methods of using the chemico-transport model of the lower atmosphere in combination with the data of the ground-based and satellite measurements of the atmosphere composition have been developed. These methods have been used to improve both the spatial distribution, and the temporal variability of the intensity of the sources that produce chemically active admixtures in the atmosphere. It has been demonstrated that the available satellite measurement data about the tropospheric content of nitrogen oxide can improve our knowledge about the sources of nitrogen oxide at relatively small scales that can be resolved within the typical regional chemico-transport model. Significant errors have been found in the available databases with conventional emission inventories for several countries in Southern and Eastern Europe (I. B. Konovalov).

As a result of using the developed method for calculation of emissions of chemicals and aerosols, the possibility of achieving satisfactory qualitative agreement between the measured day-to-day variations in the densities of several main atmosphere pollutants (carbon monoxide, suspended matter and ozone) and the calculated atmosphere pollution under the conditions of intense natural fires has been demonstrated for the first time (jointly with the Hydrometeorological Center of Russia).

Evaluations of relative variations in anthropogenic emissions of nitrogen oxides (%) in 1996—2005, which were obtained by inverse modeling based on the satellite measurement data	Evolution of the density of suspended matter in Moscow in summer 2010: REF means the calculation with no allowance for the 2010 fires, and FE means the calculation allowing for the fires

In the process of these studies, an extensive use is made of the modern three-dimensional chemico-transport model, which was adapted for qualitative description of the evolution of the atmosphere composition over the European part of Russia. The efficiency of this model has been demonstrated for solving of a wide range of practical scientific problems related to the control over and prediction of the air quality, as well as the level of the anthropogenic load on the atmosphere.

NO2 abundance in the troposphere over the Central-European region of Russia, reconstructed from the OMI satellite measurement data (top) and the analogous characteristic calculated by using the model