ISSN 00014338, Izvestiya, Atmospheric and Oceanic Physics, 2014, Vol. 50, No. 4, pp. 431–434. © Pleiades Publishing, Ltd., 2014. Original Russian Text © S.F. Abdullaev, V.A. Maslov, B.I. Nazarov, T.Kh. Salikhov, 2014, published in Izvestiya AN. Fizika Atmosfery i Okeana, 2014, Vol.50, No. 4, pp. 489–492. 431 The studies of atmospheric transparency [1, 2] made it possible to identify general patterns of the spa tial distribution and longterm oscillations of aerosol optical thickness (AOT) of the atmosphere, typical of the CIS territory. The AERONET aerosol observation network (http://aeronet.gsfc.nasa.gov) [3, 4] is one of the most operational and informative means for atmo spheric studies. The results of studies for a wide range of the spectrum were described in [5–11]. This paper analyzes the specific features of AOT obtained in Dushanbe from July 2010 to March 2011. The measurements were conducted in the eastern sub urb with a photometer located at a height of 822 m above sea level and ~16 m above the ground. The AOT measurement error was ±0.01–0.02. Out of all 9824 series of measurements conducted with a CE318 SunSky photometer in 2010 and corrected after the recalibration of the photometer, 5947 corresponded to level 2. In a clear atmosphere, the AOT minimum is reached in midday. The dustiness completely changes this characteristic. The temporal variation of AOT measured under dust haze (August 23, 2010) and nor mal background atmospheric dustiness typical for Dushanbe (August 22, 2010, and August 27, 2010) and on a clear day (March 8, 2011) is shown in Fig. 1. A more schematic and more general characteristic of the shortterm variability of aerosol transparency of the atmosphere is provided by hourly mean values of AOT (Fig. 2a). The diurnal course of the column of atmospheric turbidity was described also using the normalized values of AOT obtained as the ratio of hourly mean values of AOT τ h to daily mean values τ d (Fig. 2b). The temporal variation of the ratio of hourly mean 〈τ h 〉 (Fig. 2) and daily mean values of AOT on background (August 22, 2010) and clear (August 27, 2010) days shows the amplitude variations in AOT. The relative changes in AOT of the form 〈ε〉 = (τ max – τ min )/〈τ〉 are in the range between 31 and 47%, the changes in AOT of the form ε min = (τ max – τ min )/τ min are in the range between 38 and 64%, and the changes in AOT in the form ε max =(τ max – τ min )/τ mах are in the range between 28 and 39%. The maximum of the optical thickness τ max = 3.49 was observed in the summer intrusion of dust haze. The strong change in AOT due to dust intrusions leads to an increased scatter in the values and an increased variation coefficient V. In 2010 the variation of the average value of AOT τ av was 0.197–0.385 with a change in the standard deviation σ in the range from 0.206 to 0.243, and the variation coefficient in the range of from 0.628 to 1.044. With increasing wave length, the parameters τ and σ decrease monotoni cally and the variation coefficient increases, although its behavior in winter corresponds to the course of τ and σ, i.e., also decreases. Since V = σ/〈τ〉, this value can grow if the numerator decreases more slowly than the denominator. The cases of this “anomalous” behavior refer to the seasons when dusty haze occurs and atmospheric transparency strongly varies from measurement to measurement. The “anomalous” behavior of the variation coefficient is observed also in taiga areas of Russia [5], although the amplitudes of optical thickness here are much lower. This regularity is observed for all seasons. Figure 3 shows the spectral dependences of statistical parame Variations in Parameters of Aerosol Optical Thickness in Dushanbe S. F. Abdullaev a , V. A. Maslov a , B. I. Nazarov a , and T. Kh. Salikhov b a Umarov Institute of Physics and Technology, Tajik Academy of Sciences, ul. Aini 299/1, Akademgorodok, Dushanbe, 734063 Tajikistan b Scientific Research Institute, Tajik National University, pr. Rudaki 17, Dushanbe, 734025 Tajikistan email: sabur.f.abdullaev@gmail.com Received February 22, 2013; in final form, May 15, 2013 Abstract—The results of studies of aerosol optical thickness (AOT) in Dushanbe conducted from July 2010 to March 2011 within the AERONET program are discussed. The statistical characteristics of AOT have been shown to significantly vary during dust intrusions. The seasonal variations in the dustiness of the atmosphere have been analyzed. Keywords: AERONET, optical thickness, atmosphere, dust aerosol, dust haze DOI: 10.1134/S0001433814030025 SHORT COMMUNICATIONS