M. V. Panchenko

Characteristics of the annual behavior of the spectral aerosol optical depth of the atmosphere under conditions of Siberia

Based on multiyear observations in Tomsk (since 1995, in the wavelength range 0.37–4 μm) and other regions of the Asian part of Russia (2003–2008), we determined the specific features of the annual behavior of the characteristics of the spectral aerosol optical depth (AOD) of the atmosphere. It is shown that AOD peaks are observed in April (0.19 in the region of 0.5 μm) and July, a local minimum in June (less than 0.16), and minimum values in the fall (0.12). The seasonal variations of the Angström selectivity exponent are characterized by elevated values in the warm period (maximum in July) and low values in winter. The closeness of the seasonal variations of aerosol turbidity in three Siberian regions is noted, and the Siberia mean annual behavior of atmospheric AOD characteristics is suggested. The average values of the aerosol optical and microphysical characteristics of the atmospheric depth for characteristic periods of intraannual AOD variations are presented.

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.

Optical–microphysical properties of smoke haze from Siberian forest fires in summer 2012

A comprehensive experiment on the study of dynamics of optical and microphysical characteristics of submicron aerosols in the near-ground air layer was carried out in June–August of 2012 under conditions of extremely strong smoke haze originating from vast forest fires in Siberia. Variations of the spectral angular scattering coefficients and the degree of linear polarization in the visible wavelength range are studied, as well as the mass concentrations of dry fractions of aerosol and black carbon, relative content of black carbon (BC fraction), single scattering albedo, particle size distribution function, complex refractive index of the particulate matter, and parameter of condensation activity of aerosol. Peculiarities of differences between optical and microphysical characteristics of near-ground aerosol in smoke haze and under smokeless conditions are revealed. This study is important for validation of results of remote sensing of the composition of smoke haze and background atmosphere obtained from satellite data and sun photometric measurements at the Aerosol Robotic Network (AERONET).

Aerosol optical and microphysical properties over the Atlantic Ocean during the 19th cruise of the Research Vessel Akademik Sergey Vavilov

[1] This paper presents aerosol optical depths in the total atmospheric column, aerosol size distributions, number concentrations and black carbon mass concentrations at the deck level measured in October–December 2004 on board the R/V Akademik Sergey Vavilov. Aerosol optical depths measured within the spectral range 0.34–4.0 mm were close to background oceanic conditions (0.04–0.08) in the high-latitude southern Atlantic. Angstrom parameters derived within 440–870 nm and 870–2150 nm spectral ranges did not exceed 0.6, yielding averages of 0.34 and 0.12, respectively. The mass concentration of black carbon varied within the range 0.02–0.08 mg/m 3 in the 34–55S latitudinal belt. The average of 0.04 mg/m 3 (s.d. 0.015) is close to the reported results for the remote areas of the South Indian Ocean. Aerosol volume size distributions measured within the size range of 0.4–10 mm can be characterized by a geometric volume mean radius 3 mm. This is consistent with the columnar retrievals reported by the Aerosol Robotic Network (AERONET).

Investigation of spectral dependence of shortwave radiation absorption by ambient aerosol using time-resolved photoacoustic technique

The method of time-resolved photoacoustic spectroscopy is applied to study the weak aerosol absorption of shortwave radiation in the atmospheric air. Using synchronous measurements of aerosol light absorption coefficients by a pulsed photoacoustic spectrometer and mass concentration of black carbon by an Aethalometer, we determine the values of the efficiency σ of aerosol light absorption in the atmospheric air in the shortwave spectral range for three wavelengths: σ (0.532 µm)=(5.49±3.57)m 2 g –1 , σ(0.694 µm)=(4.46±2.61)m 2 g –1 , and σ(1.064 µm)=(2.87±1.84)m 2 g –1 . The experimental results are approximated by the spectral dependence σ(λ)=3.1λ– 0.92 , where wavelength λ is expressed in micrometers. We discuss the calibration procedure for the pulsed photoacoustic spectrometer in studying the aerosol absorption.

Diurnal variations of the submicron aerosol and black carbon in the near-ground layer

Peculiarities of seasonal variability of diurnal variations of the mass concentrations of submicron aerosol and black carbon (BC) in the near-ground layer have been analyzed based on the measurements carried out in 1997–2008 at the aerosol station of the Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (Tomsk). The shape of aerosol and BC diurnal variations are the same for all seasons, with morning and evening maxima and nighttime and daytime minima. The maxima in the diurnal variations of aerosol concentration approach each other in winter and move away from each other in summer. Shape stability of the BC diurnal variations in different seasons is an indicator of stable diurnal dynamics of the aerosol absorption coefficient in the visible spectrum. Some differences in the diurnal variations of aerosol and BC make it possible to draw a conclusion about the presence of a certain BC fraction in the form of external admixture. All extremums of the diurnal aerosol and BC variations clearly manifest in the cloudless atmosphere; however, the diurnal variations become smooth in continuous cloudiness. In this case, the morning maximum of aerosol becomes statistically insignificant in different seasons.

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.

Seasonal variability of the vertical profiles of absorption parameters of submicron aerosol in the troposphere

The seasonal variability of the vertical profiles of concentrations of aerosol and black carbon (BC), the BC fraction, the single scattering albedo, and the imaginary index of refraction of particulate matter are studied based on long-term airborne measurements of the scattering coefficient of dry matter of aerosol particles at a wavelength of 0.51 μm and the mass concentration of BC in the troposphere up to a height of 7 km in the southern part of Novosibirsk region. It is shown that the lower (up to 1.5 km) and upper (above 1.5 km) layers of the troposphere are extremely different in their absorption properties of aerosol. In the lower layer, in winter and autumn, mean values of the BC fraction decrease with height in a wide range from 13 to 5%. The values of albedo increase with height, varying in the range from 0.8 to 0.94. In the lower layer, in winter, aerosol particles have strong absorption. The value of the imaginary index of refraction has the greatest values, about 0.09, in the near-ground layer, and decreases with height to values of 0.03. In the upper layer, the values of the BC fraction vary more weakly, in the range of 2–5%. The range of seasonal and altitudinal variations of the albedo becomes narrower (0.92–0.97) and the values of the imaginary index of refraction vary in the range from 0.03 to 0.01, i.e., aerosol particles in the upper air layer are comparatively weakly absorbing. Estimates of the variability of the aerosol radiative parameters are evidence of a certain independence of the behavior of the BC component at the formation of the vertical profiles of the concentrations of aerosol and BC.

Multiyear variations in aerosol condensation activity in Tomsk

We consider the results of 13 years (1998–2010) of studies of the aerosol condensation activity in Tomsk. The long-term behavior of the condensation activity parameter exhibits, in addition to the annual cycle and its second harmonic, a tendency toward slower, ∼6–7-year oscillations. The values were maximum in 1998–1999 and 2005–2007. The annual average values were minimum in 2003 and 2008, i.e., in years when intrusions of subtropical air masses from arid regions of Kazakhstan and Central Asia were the most frequent.

Seasonal behavior of the CO2 gas exchange process in the “atmosphere-water” system of the littoral zone of southern Baikal. 1. Hydrological spring

Analysis of the mechanisms determining the direction and intensity of CO2 fluxes in the “atmosphere-water” system seems to be important in the context of studying the problem of present-day increase in the content of one of the greenhouse gases (carbon dioxide) in the atmosphere. This paper starts a series of publications devoted to the analysis of seasonal features of the CO2 gas exchange process in the littoral zone of southern Baikal and presents the results obtained in the spring period.It is shown that the greatest transformation of all components of the carbon dioxide gas exchange process between the water surface and the atmosphere is observed during “hydrological spring” period in the littoral zone of Lake Baikal. The amplitude of the diurnal behaviors of the CO2, O2, and N3− concentrations in water increases from May to June. The diurnally average CO2 flux, which is directed to the atmosphere in mid-May, changes its direction as soon as June, and a distinct CO2 sink to the water surface becomes evident. The tendency toward increase in the amplitude of the diurnal CO2 behavior in water and enhancement of the carbon dioxide sink from the atmosphere to the water surface continues; that the sink, on average, may reach 70 mg CO2 m−2 day−1 by mid-July.