Complex experiment on studying the microphysical, chemical, and optical properties of aerosol particles and estimating the contribution of atmospheric aerosol-to-earth radiation budget

The primary objective of this complex aerosol experiment was the measurement of microphysical, chemical, and optical properties of aerosol particles in the surface air layer and free atmosphere. The measurement data were used to retrieve the whole set of aerosol optical parameters, necessary for radiation calculations. Three measurement cycles were performed within the experiment during 2013: in spring, when the aerosol generation is maximal; in summer (July), when atmospheric boundary layer altitude and, hence, mixing layer altitude are maximal; and in late summer/early autumn, during the period of nucleation of secondary particles. Thus, independently obtained data on the optical, meteorological, and microphysical parameters of the atmosphere allow intercalibration and inter-complement of the data and thereby provide for qualitatively new information which explains the physical nature of the processes that form the vertical structure of the aerosol field

Statistical Estimation of the Atmospheric Aerosol Absorption Coefficient Based on the Data of Optical Measurements

The problem of the choice of the aerosol optical constants and, in particular, imaginary part of the refractive index of particles in visible and infrared (IR) wavelength ranges is very important for calculation of the global albedo of the atmosphere in climatic models. The available models of the aerosol optical constants obtained for the prescribed chemical composition of particles (see, for example, Ivlev et al. 1973; Ivlev 1982; Volz 1972), often are far from real aerosol. It is shown in (Krekov et al. 1982) that model estimates of the optical characteristics of the atmosphere depending on the correctness of real and imaginary parts of the aerosol complex refractive index can differ by some hundreds percent. It is known that the aerosol extinction coefficient {alpha}({lambda}) obtained from measurements on a long horizontal path can be represented as {alpha}({lambda})={sigma}({lambda})+{beta}({lambda}), where {sigma} is the directed light scattering coefficient, and {beta} is the aerosol absorption coefficient. The coefficient {sigma}({lambda}) is measured by means of a nephelometer. Seemingly, if measure the values {alpha}({lambda}) and {sigma}({lambda}), it is easy to determine the value {beta}({lambda}). However, in practice it is almost impossible for a number of reasons. Firstly, the real values {alpha}({lambda}) and {sigma}({lambda}) are very close to each other, and the estimate of the parameter {beta}({lambda}) is concealed by the errors of measurements. Secondly, the aerosol optical characteristics on the long path and in the local volume of nephelometer can be different, that also leads to the errors in estimating {beta}({lambda}). Besides, there are serious difficulties in performing spectral measurements of {sigma}({lambda}) in infrared wavelength range. Taking into account these circumstances, in this paper we consider the statistical technique, which makes it possible to estimate the absorption coefficient of real aerosol on the basis of analysis of simultaneous measurements of the spectral aerosol extinction coefficients {alpha}({lambda}), the directed scattering coefficient of dry aerosol {sigma}{sub 0}(0.55) and the mass concentration of aerosol containing BC (black carbon) Ms

Studies of atmospheric aerosols in the Russia Arctic regions

Chemical composition of snow and ice in the Arctic depends, to a considerable extent, on chemical composition of aerosol particles. Analysis of atmospheric aerosol characteristics in the boundary layer near Arctic settlements Tiksi (Summer 2010) and Barentsburg (Spring–Summer 2011) have been investigated. The results contain the outcome of number concentration measure (NA), aerosol optical thickness of the atmosphere, and chemical composition of the water soluble aerosol fraction. Level of aerosol concentration in the boundary layer of the tested points is rather low, and characterized by the following number concentration values: in Tiksi –NA = 1,80±4,5 μg∙cm−3, in Barentsburg – spring – 4,95±3,49 μg∙cm−3, summer – 3,66±3,13 cm−3. Aerosol optical thickness of the atmosphere is characterized by rather low values, and low changeability as compared with continental areas of middle latitudes. Seasonal changes in the aerosol optical thickness of the atmosphere near Barentsburg conforms with earlier obtained data in the Arctic regions. Mean value of Ångstrom selectivity indicator amounted to 1.28 in spring, and to 1.42 in summer. Mean total concentration of ions in aerosols near Tiksi (2.4±1.6 μg∙m−3) is quantitatively correlated with ions total in aerosols near Barentsburg for spring season (2.8±1.4 μg∙m−3). In the water soluble fraction of aerosols is dominated the concentration of ions both marine (Na+, Cl−), and continental (NH4+, SO42−, NO3−) origin. Chemical composition of aerosols in Tiksi and Barentsburg is similar to aerosols composition in the Antarctic coast regions