M. A. Sviridenkov

Active spectral nephelometry as a method for the study of submicron atmospheric aerosols

The approach to the investigation of submicron atmospheric aerosol properties, developed over many years and conventionally called ‘the method of active spectral nephelometry’, is described in this paper. This approach is based on the principle of the separate study of the processes of variability of the dry matter of aerosol particles under the effect of external geophysical factors and their condensation activity supplemented by improved investigation of the physicochemical properties of particles by means of artificial influences and the technique for solving the inverse problem. Techniques for measurements and interpretation of data are presented, including solving the inverse problems of light scattering. The efficiency of the method for the study of the parameter of condensation activity and the growth factor of particles is shown based on the data of measurements in the real atmosphere. The results of thermo‐optical investigations of a submicron aerosol are presented. Seasonal and interannual behaviours of the optical parameters measured and microphysical characteristics of aerosol in the near‐ground layer of the atmosphere of west Siberia are analysed using the data from long‐term observations.

Satellite and ground-based monitoring of smoke in the atmosphere during the summer wildfires in European Russia in 2010 and Siberia in 2012

Using Moderate Resolution Imaging Spectroradiometer (MODIS) (Aqua and Terra satellites) and in situ observations, a comparative analysis of two large-scale smoke events caused by the summer wildfires in European Russia (ER) in 2010 and Western Siberia (WS) in 2012 was carried out. In the 5-day periods of the extreme smoke pollution (5–9 August 2010 in ER and 27–31 July 2012 in WS), the number of active fires in the equal territories, confined by the coordinates 47°–65° N, 25°–55° E and 51°–70° N, 71°–104° E, was found to be 4754 for ER and 3823 for WS. With this, the regional mean aerosol optical depths (AODs) were found to be (1.02 ± 0.02) and (1.00 ± 0.04), not much differing for both the events. The regional mean aerosol radiative forcing effects at the top (R1) and the bottom (R2) of the atmosphere over ER/WS according to MODIS observations were estimated to be (−61 ± 1) and (−54 ± 2) W m−2, and (−107 ± 2) and (−96 ± 3) W m−2, respectively. At the same time, the local values of AOD and the local absolute values of R1 and R2 over WS were considerably higher than those over ER. MODIS AOD (L3) data during the wildfires of 2010 were validated by AOD data obtained by the sun-sky photometer CIMEL, operating at the AERONET station Zvenigorod. The rates of radiative heating of the smoky atmosphere over ER and WS were also estimated and compared with the existed temperature anomalies, obtained using National Centers for Environmental Prediction National Center for Atmospheric Research reanalysis data. Optical and microphysical properties of smoke aerosols during the wildfires in ER and WS also revealed some similar characteristics. The aerosols were mostly found in the submicron-size fraction and characterized by very high single-scattering albedos (0.95–0.98). In the dense smoke conditions, the degree of linear polarization at the scattering angle 90° during both the events decreased to negative values ranging between −0.1 and −0.15. The optical properties of smoke aerosols were mainly conditioned by unusually narrow particle size distribution.

Retrieval of aerosol optical and microphysical characteristics according to data of ground-based spectral measurements of direct and scattered solar radiation. Part 1. Testing of algorithm

The ground-based measurements of direct and scattered solar radiation to date serve as the most reliable source of information on the columnar optical and microphysical characteristics of atmospheric aerosols. We suggest an algorithm which combines the iteration retrieval of the optical single-scattering characteristics directly from the data of photometric measurements and the solution of the linear inverse problem which ensures the retrieval of the microstructure of homogeneous aerosol particles and complex refractive index of the aerosol material. Software, developed to make the routine experimental data processing more efficient, is described. Results of algorithm testing on different mono- and multi-component aerosol models are presented.

Aerospace monitoring of smoke aerosol over the European part of Russia in the period of massive forest and peatbog fires in July–August of 2010

Based on MODIS satellite observations of aerosol optical depth (AOD) and active fires, as well as on data from the network for aerological radio sounding, we analyzed the spatiotemporal evolution of smoke aerosol on the territory of European Russia (ER) during the period of massive forest and peatbog fires in summer of 2010. An interrelation is found between the structural features of the smoke-polluted regions and the processes of large-scale dynamics. The evolution of the smoke aerosol plume in the metropolitan area is described in detail. The statistical characteristics of AOD variations over ER during the fire period are calculated. The total column smoke aerosol is estimated. The radiation effects of smoke pollution of the atmosphere in the region are studied. The time evolution of the regional average shortwave radiative forcing of smoke aerosol at the top and bottom of the atmosphere is presented, together with the spatial distribution of local values of the radiative forcing in the period of maximum smoke pollution of ER. A statistically significant relation is found between MODIS-diagnosed number of active fires and wind speed and direction. The MODIS data on AOD are validated against observations at the AERONET station in Zvenigorod.

Retrieval of aerosol optical and microphysical characteristics according to data from ground-based spectral measurements of direct and diffuse solar radiation. Part 2. Algorithm testing

We present the results of the study of sensitivity of our algorithm for retrieving the columnar aerosol optical and microphysical characteristics to measurement errors. The algorithm testing against data from field measurements under conditions of both increased and moderate aerosol turbidity of the clear sky atmosphere is discussed. We present the average values of the aerosol optical and microphysical characteristics retrieved according to data from photometric measurements at the AERONET station in Tomsk during 2004–2009 for situations when the aerosol optical depth in the spectral channel of 440 nm did not exceed 0.4.

Retrieval of atmospheric aerosol parameters from data of a three-wavelength integrating nephelometer

Possibilities of retrieving a true value of the scattering coefficient and particle size distribution from data of a three-wavelength integrating nephelometer are analyzed. Two approaches to evaluation of the ratio of the true scattering coefficient to the measured one are suggested. Comparison of the aerosol micro-structure obtained from data of simultaneous measurements with an integrating nephelometer and with a nephelometer-polarimeter PhAN is carried out. The PhAN data are compared with measurements with a differential mobility analyzer.

Moscow smoke haze in October 2014. Variations in the aerosol mass concentration

Variations in the aerosol mass concentration in the smoky atmosphere of the Moscow region in autumn 2014 have been analyzed. The soot mass fraction and ratio between the PM2.5 and PM10 mass concentrations were typical of the fires in boreal forests. The smoke event in the Moscow region was due to the long-range transfer of the smoke aerosol, which was confirmed by a joint analysis of aerospace monitoring data and inverse trajectories of air mass transfer, and local fires in the Moscow region. As a result, statistical parameters of variations in the smoke aerosol mass concentrations were atypical, including empirical distribution functions and power spectra.

Relationships between the optical and microphysical parameters of near-ground aerosol condensation activity

The results of measurements of the dependences of the aerosol optical characteristics on the relative humidity of air in artificial condensation processes are analyzed. The dependences of the condensation growth factors on the dry particle size are calculated and their statistical analysis is performed. The regression relation between the measured optical parameters of condensation activity and the Hanel parameter for the aerosol volume concentration is obtained. The possibility of the estimation of the Hanel parameter from the values of the refractive index of dry and humidified particles is shown.

Parameterization of asymmetry factor of atmospheric aerosol scattering phase function

We analyzed how the asymmetry factor of the atmospheric aerosol phase function can be estimated from spectral measurements of light attenuation and scattering. An empirical formula is suggested to parameterize the asymmetry factor as a function of the Ångström exponent and complex refractive index. Several approaches to determining the asymmetry factor from data of integrating nephelometers are considered. An analytical formula, relating the asymmetry factor to the nephelometer-measured ratio of the radiative fluxes scattered into the forward and backward hemispheres, is derived. The asymmetry factor at three wavelengths is calculated according to data of field measurements in St. Petersburg suburbs in 2015.

Aerosol scattering phase function for the arid territory of southeast Kazakhstan

The paper describes a method of extracting the aerosol scattering phase function from absolute scattering phase function of brightness, measured in the solar almucantar in the total absence of clouds in the sky. The method is tested on archive observation data, obtained in the semiarid region in southeast Kazakhstan in the visible spectral range. We present the calculations of the directional aerosol scattering coefficients and the corresponding typical aerosol particle size distribution functions. It is shown that these functions are similar to the data from the Solar Village site (Saudi Arabia) of Baseline Surface Radiation Network.