**1. Introduction**

Investigation results of the atmospheric aerosol over the Russia territory are of great interest for the ecology and climate developments. The regularities of spatial and temporal variations in the Aerosol Optical Depth (AOD) and Air Turbidity Factor (T) can be received by the Russian actinometric network data (RussianHydrometeorologicalResearchCenter). Our analysis will be based on the "Atmosphere Transparency" special-purpose database created at the Voeikov Main Geophysical Observatory (MGO) on the basis of observational actinometric data. Author has many years cooperation with MGO in the region of the processing and analysis of these observation data. The relationship between the increases in the global surface air temperature and in the atmospheric content of greenhouse gases has been proven. The warming over the past 50 years has mainly been related to human activities (IPCC, Climate Change 2001, 2007). Along with the anthropogenic factor, climate is affected by such natural factors as variations in the solar constant, cyclic interactions between the atmosphere and the ocean, and atmospheric aerosol; these factors are pronounced within time intervals of several years to several decades. The sign of aerosol forcing may be different: the stratospheric aerosol layer causes the reflection of solar radiation incident upon the atmospheric upper boundary and, thus, decreases the warming of the underlying air layers. For example, the sulfate aerosol which formed in the stratosphere after the Pinatubo eruption (June 1991) caused "short" (in 1993) global cooling. Tropospheric aerosol can increase or decrease the surface air temperature, and its influence on the ecological state of the air is well understood (Isaev, 2001). Therefore, monitoring the atmospheric aerosol component is important and necessary now from the standpoints of its

© 2012 Plakhina, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Plakhina, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Hoshiko et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons

climatic forcing and ecology. The study of current spatiotemporal variations in the atmospheric aerosol component is of scientific interest and presents a problem. Current ground-based networks of monitoring (in particular, AERONET) are the results of such interest (Holben et al., 1998). There are eight AERONET stations in Russia; seven of them are located in Siberia [8]. The maps, which show a global distribution of the sources of different anthropogenic, natural, organic, mineral, marine, and volcanic) aerosols arriving in the atmosphere, the total aerosol optical depth in the atmospheric thickness according to model data (IPCC, Climate Change 2001) and the aerosol optical depth according to satellite (MODIS) monitoring (IPCC, Climate Change 2007), show Russia as a territory of decreasing aerosol optical depth (AOD) going from south to north. At the same time, Russia occupies the entire northeastern part of Eurasia ( 30°E –180°E; 50°N – 80°N) and includes different climatic zones which differ in water content, air temperature, cloudiness, solar radiation flux incident upon the land surface, underlying surface, and air-mass circulation. In addition, the density of population and the degree of industrialization of different Russian regions are very inhomogeneous in space. In the studies (Plakhina et al., 2007, 2009) we have shown that an analysis of the AOD of a vertical atmospheric column can be made on the basis of observational data obtained at the Russian actinometric network, in particular, on the basis of data on the integral atmosphere transparency ( *P* ), because *P* variations are, to a great extent, determined by the aerosol component of the attenuation of direct solar radiation; other components of the attenuation (water vapor and other gases) have little effect on its time variations. Thus, on the basis of data on the homogeneous (calibrated against a single standard and obtained with a unified method) observational series of direct solar-radiation fluxes at the land surface and estimates of the integral (total and aerosol) transparency, it is possible to analyze variations in the AOD of a vertical atmosphere. Now we continue this analysis on the basis of an extended database (the number of stations -- 53, and the period of observations – 1976 -2010 years. Now we present the character of multiyear seasonal variations in AOD, the simplest statistical parameters (means, extrema, and variation coefficients) of spatial variations in AOD annual means, the "purification" of the atmosphere from aerosol over the past 15 years (1995-2010 y.y.). Also we compare the effects of the two natural factors (the global factor—the powerful volcanic eruptions in the latter half of the 20th century which resulted in the formation of a stratospheric aerosol layer and the regional tropospheric factor—for example, the arrival of aerosol in the atmosphere due to tundra and forest fires) on AOD.

Variations in the Aerosol Optical Depth Above the Russia

from the Data Obtained at the Russian Actinometric Network in 1976–2010 Years 5

advection of air masses from the regions with an increased or decreased aerosol load, volcanic eruptions, and forest and tundra fires. In analyzing the 1976–2010 observational data, our goal was to obtain an averaged pattern of the spatial distribution of atmospheric aerosol over Russia and to compare this pattern with that of the global aerosol distribution which is presented in the IPCC third (modeling) and fourth (satellite data, MODIS) reports (IPCC, Climate Change 2001, 2007). In this case, the estimates obtained with our method supplement the international data on the model approximations and satellite monitoring of AOD. The advantages of our estimates are the great length of the series of actinometric observations under consideration (35 years), the universal methods of measurements and data treatment for all the stations, and the vast coverage area of Russia's large territory.

**Figure 1.** Layout of 53 actinometric stations whose data will be analyzed in the chapter. It is possible

The special-purpose Atmosphere Transparency database formed at the Main Geophysical Observatory makes it possible to analyze both the integral and aerosol transparencies of the atmosphere. The stations given in Fig. 1 were selected with consideration for the quality and

Where Sis the direct solar radiation to the normal-to-flux surface, reduced to the average distance between the Earth and the Sun and a solar altitude of 30°; *S*0is the solar constant

T = lgP / lgPi = ( lgS0 – lgS ) / ( lgS0 – lgSi ) = -lg P / 0.0433 (2)

equal to 1.367 kW/m2. The Linke turbidity factor is unambiguously correlated with Р:

P = (S/S0)1/2 (1)

that the list of the observation stations will be increased up to 80 for the special estimations.

completeness of the instrumental series. The integral air transparency :

**3. Empirical data and analysis procedure** 

## **2. Russian actinometric network data**

Fig. 1 gives a map showing the location of 53 actinometric stations of the Russian network (Makhotkina et al., 2005, 2007; Luts'ko et al., 2001)for which the AODs of vertical atmospheric columns were estimated for a wavelength of 0.55 μ from the measured fluxes of direct solar radiation at land surface. These stations cover a large part of Russia and are located outside the zones of direct local anthropogenic sources of industrial and municipal aerosol emissions (suburbs, rural areas, uplands, etc.). In other words, the considered spatiotemporal variations in AOD are formed under the influence of natural factors: the advection of air masses from the regions with an increased or decreased aerosol load, volcanic eruptions, and forest and tundra fires. In analyzing the 1976–2010 observational data, our goal was to obtain an averaged pattern of the spatial distribution of atmospheric aerosol over Russia and to compare this pattern with that of the global aerosol distribution which is presented in the IPCC third (modeling) and fourth (satellite data, MODIS) reports (IPCC, Climate Change 2001, 2007). In this case, the estimates obtained with our method supplement the international data on the model approximations and satellite monitoring of AOD. The advantages of our estimates are the great length of the series of actinometric observations under consideration (35 years), the universal methods of measurements and data treatment for all the stations, and the vast coverage area of Russia's large territory.

**Figure 1.** Layout of 53 actinometric stations whose data will be analyzed in the chapter. It is possible that the list of the observation stations will be increased up to 80 for the special estimations.
