D. G. Chernov

Estimation of Aerosol Radiation Effects under Background and Smoke-haze Atmospheric Conditions over Siberia from Empirical Data

The results of numerical simulation of downward solar radiation fluxes for background and smoke-contaminated atmospheric conditions are discussed. Vertical profiles of aerosol characteristics are obtained from the empirical model based on the data of aircraft sounding of profiles of angular scattering coefficients and content of absorbing particles in the lower troposphere. The background model was created using the results of measurements obtained under cloudless and mostly cloudless atmospheric conditions in 1999–2011. Optical parameters of smoke aerosol are determined from the data of aircraft measurements in the period of long-term wildfires in Siberia in the summer 2012. It is demonstrated that deficiency in diurnal values of total solar radiation at the surface level caused by the formation of the optically dense smoke layer as compared to background conditions, is more than 13 MJ/m2.

Model Estimates of Dynamics of the Vertical Structure of Solar Absorption and Temperature Effects under Background Conditions and in Extremely Smoke-Laden Atmosphere According to Data of Aircraft Observations

We present the quantitative estimates of the vertical distribution of absorbed solar radiation and temperature effects in the background and extremely smoke-laden troposphere of Siberia, obtained using empirical data and numerical simulation. Vertical profiles of the aerosol characteristics are created based on an empirical model, relying on aircraft sensing of angular scattering coefficients and the content of absorbing particles at different altitudes. It is shown that, under the smoke-haze conditions, the radiation effect of aerosol particles with high black carbon content on the diurnal influx of solar radiation in the central part of the smoke layer exceeds 50%. The change in air temperature due to the absorption of solar radiation during the daylight hours is approximately 2.5–5.5 K when the optical depth of the smoke aerosol varies in the range 2 ≤ τsmoke(0.55 μm) ≤ 4.

Generalization of Results of Atmospheric Aerosol Optical Depth Measurements on Spitsbergen Archipelago in 2011–2016

We discuss the results of spectral measurements of aerosol optical depth (AOD) of the atmosphere, carried out in warm periods of 2011–2016 in the Arctic settlement Barentsburg (Spitsbergen Archipelago). The statistical characteristics of seasonal and interannual variations in atmospheric AOD in the wavelength range of 0.34–2.14 μm are presented. The average AOD (0.5 μm) over the six-year period of observations had been 0.086, and, in particular, the fine mode AOD component had been 0.062 and the coarse mode AOD component had been 0.024. It is shown that the seasonal variations were best manifested in the decrease of modal (most probable) values of fine mode AOD component from 0.055 in spring to 0.025 in autumn. As compared to the preceding (pre-2011) period, we noted a closer convergence in the average AOD values between spring and summer, primarily due to a decrease in the content of fine mode aerosol in spring and its increase in summer. The summertime AOD growth is most likely due to episodic outflows of smoke aerosol from boreal zones of Eurasia and North America.

Annual dynamics of the black carbon size distribution in the near-ground submicron aerosol in western Siberia

The results of the round-the-clock measurements of the size distribution of equivalent black carbon in the near-ground submicron aerosol of Western Siberia in 2014-2016 are analyzed. The results were obtained with the diffusion BC spectrometer developed by us. It was found that, in the approximation of unimodal lognormal function, the annual dynamics of the monthly average BC size distributions is characterized by the year-to-year stability and shows winter maxima and summer minima of the BC volume median diameter and the distribution amplitude. The BC median diameter varies from 140 to 220 nm, and the distribution amplitude ranges from 0.4 to 3.4 μm3/cm3. A significant increase in the diurnal average values of the BC median diameter was observed under conditions of income of smokes from forest fires to the measurement site.

Differences in seasonal average concentrations of aerosol and Black Carbon and particle size distributions from the data of monitoring in Tomsk and under background conditions in 2014-2015

The mass concentrations of the dry basis of aerosol and Black Carbon (November 2013 – December 2015) and the volume particle size distributions (2015) measured in the monitoring mode under background conditions (Fonovaya (Background) Observatory, 60 km west of Tomsk) and under urban conditions (Akademgorodok District of Tomsk) have been used to determine the average seasonal contribution of the city to the aerosol characteristics. It has been found that the annual profile of the seasonal average city contribution to the aerosol and Black Carbon (BC) contents, as well as the volume fill factor of the submicron aerosol, has a maximum in winter and a minimum in summer. In the coarse size range, the maximal excess of the volume fill factor was observed in the spring period. The observed differences between the city and the background conditions for the relative content of Black Carbon in aerosol and the absorption coefficient of the particulate matter were largest in summer and smallest in winter. Under the background conditions, the annual behavior had an untypical feature, namely, the seasonal average aerosol concentrations in summer exceeded the values obtained for the spring and autumn seasons. Analytical parameterization of the annual profile of monthly average difference of the urban and background mass concentrations of aerosol and Black Carbon in the form of parabolic dependence has been proposed.

Investigation of microphysical characteristics and chemical composition of near-ground aerosol in Barentsburg (Spitsbergen) in the spring and summer seasons of 2011-2015

Since 2011, the Institute of Atmospheric Optics (IAO SB RAS, Tomsk) and the Arctic and Antarctic Research Institute of the Russian Federal Service for Hydrometeorology and Environmental Monitoring (AARI, St. Petersburg) conduct field studies of near-ground aerosol characteristics at the Spitsbergen archipelago (Barentsburg) in the spring and summer seasons. The following parameters are measured in the atmospheric surface layer: aerosol particle number density and volume particle size distribution; mass concentrations of aerosol and absorbing matter (black carbon); coefficients of total aerosol scattering and aerosol backscattering in the visible spectral region. The experimental findings obtained in 2011– 2015 are reported. Peculiarities of the seasonal and year-to-year variability of the aerosol characteristics are revealed. The results of investigation of the chemical composition of the near-ground aerosol in Barentsburg are discussed.

Temporal dynamics of optical-microphysical characteristics of atmospheric aerosol at the Spitsbergen Archipelago in 2011-2014

In 2011–2014, the Institute of Atmospheric Optics (IAO SB RAS, Tomsk) and the Arctic and Antarctic Research Institute (AARI, St. Petersburg) conducted field investigations of the near-ground aerosol characteristics near Barentsburg (Spitsbergen Archipelago) in the spring and summer seasons. The particle number density in the size range 0.3-20 μm, size distribution of particles, and mass concentrations of aerosol and black carbon were measured round-the-clock every hour with Grimm 1.108 and 1.109; and AZ-10 optical counters. The mass concentration of black carbon was measured by the MDA-02 aethalometer developed by the IAO SB RAS. Series of observations are obtained, annual and seasonal average values and their standard deviations are estimated, and seasonal and annual dynamics of the studied parameters is analyzed. Peculiarities of the temporal dynamics of average values of the aerosol characteristics are revealed and compared with the data of observations at other stations of the Spitsbergen Archipelago and in different regions of the Russian Arctic and Subarctic.

Detection of aerosol plumes from associated gas flaring by laser sensing

A cycle of the TU-134 “Optik” aircraft-laboratory flights was carried out was carried out in the frameworks of investigations of radiative and climatic changes in sub-Arctic regions of Siberia. The vast aerosol plume was observed from onboard the aircraft using the data of laser sensing. Comprehensive analysis of the results of measurements of aerosol and gaseous components of the atmosphere and the accompanying data allowed us to reveal the nature of appearance of this plume from associated gas burning.

Spatial variability of aerosol and black carbon concentrations in the troposphere of the Russian Arctic

A cycle of flights of the Optik TU-134 Flying Laboratory of IAO SB RAS over regions of Western Siberia and the Russian Arctic (55.0–74.8°N, 61.3–82.9°Е) was carried out on October 15-17 of 2014 within the framework of the YAK-AEROSIB Russian—French Project. The mass concentrations of submicron aerosol and Black Carbon (BC) in the troposphere up to a height of 8.5 km were measured in the flights. The ranges of variability were 0.3-20 μg/m3 for the aerosol concentration and 0.02-1 μg/m3 for the BC concentration. In the subpolar latitudes of 71-74.8°N, the lower levels of aerosol (0.8-6 μg/m3) and BC (0.02-0.3 μg/m3) were observed. The comparison of the results of airborne sensing in 2008 and 2014 has shown that in the Western Subartic the aerosol and BC concentrations in the vertical profiles up to six times exceeded those observed in the Eastern Subarctic (0.3-1 μg/m3 and 10-50 ng/m3). The excess of the mean integral BC concentrations and the aerosol optical depth was, on average, 2-2.5 times (0.16 mg/m2; 0.02). In the region of the Kara Sea at heights of 0.5-2 and 4-6 km, the excess of the aerosol content in the western sector in comparison with the eastern one was, on average, 2 times, while for the black carbon the excess achieved 7 times at heights of 1-2 km (0.25- 0.035 μg/m3). The mean integral concentrations of aerosol and black carbon ∼ 1.3 times exceeded those in the clearer eastern region of the sea (0.31 mg/m2; 0.049). The obtained estimates indicate the decrease of the aerosol and BC concentrations in the subpolar latitudes of the Russian Federation from the west to the east.

Complex experiment on the study of microphysical, chemical, and optical properties of aerosol particles and estimation of atmospheric aerosol contribution in the Earth radiation budget

The main aim of the work was complex experimental measurements of microphysical, chemical, and optical parameters of aerosol particles in the surface air layer and free atmosphere. From the measurement data, the entire set of aerosol optical parameters was retrieved, required for radiation calculations. Three measurement runs were carried out in 2013 within the experiment: in spring, when the aerosol generation maximum is observed, in summer (July), when the altitude of the atmospheric boundary layer is the highest, and in the late summer – early autumn, when the second nucleation period is recorded. The following instruments were used in the experiment: diffusion aerosol spectrometers (DAS), GRIMM photoelectric counters, angle-scattering nephelometers, aethalometer, SP-9/6 sun photometer, СЕ 318 Sun-Sky radiometer (AERONET), MS-53 pyrheliometer, MS-802 pyranometer, ASP aureole photometer, SSP scanning photometer, TU-134 Optik flying laboratory, Siberian lidar station, stationary multiwave lidar complex LOZA-M, spectrophotometric complex for measuring total ozone and NO2, multivariable instrument for measuring atmospheric parameters, METEO-2 USM, 2.4 AEHP-2.4m station for satellite data receive. Results of numerical calculations of solar down-fluxes on the Earth’s surface were compared with the values measured in clear air in the summer periods in 2010—2012 in a background region of Siberian boreal zone. It was shown that the relative differences between model and experimental values of direct and total radiation do not exceed 1% and 3%, respectively, with accounting for instrumental errors and measurement error of atmospheric parameters. Thus, independent data on optical, meteorological, and microphysical atmospheric parameters allow mutual intercalibration and supplement and, hence, provide for qualitatively new data, which can explain physical nature of processes that form the vertical structure of the aerosol filed.