Elena P. Yausheva

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).

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.

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 variability of diurnal behavior of concentrations of submicron aerosol and absorbing substance in coordinates of sun elevation

Main regularities of the normalized (to the daily mean values) diurnal behaviors of the concentrations of the aerosol dry matter and soot (black carbon, BC) in the near-ground air layer in Siberia are revealed on the basis of long-term measurements at the aerosol monitoring station of IAO SB RAS. It is revealed that the diurnal behavior at radiative type of weather is the same in all seasons and contains morning and evening maximums and nighttime and daytime minimums. The positions of maximums in the diurnal behaviors and their amplitudes show stable seasonal variability which is observed as approaching of the maximums in winter (9-11 a.m. and 8 p.m.) and their moving from each other in summer (7-9 a.m. and 10-11 p.m.). The differences in diurnal behaviors of aerosol and soot lie in the fact that the morning maximum of the concentration of soot is better pronounced than aerosol in all seasons. These signs are evidence of some independence of diurnal dynamics of BC and submicron aerosol. A new approach is proposed and tested for description of the diurnal behaviors of the aerosol characteristics as functions of a parameter related with solar radiation. It is shown that the normalized sun elevation as such parameter is effective for analysis of the structure of diurnal behavior. The extremes of the diurnal behavior are closely related with the characteristic values of the normalized sun elevation. Statistically significant decrease of the daily mean variation coefficients of aerosol and soot occurs is all seasons in the sun related coordinates. The greatest changes are observed in spring and autumn (up to 6). It provides for some promises for decreasing the errors in parameterization of the diurnal behaviors of the concentrations of aerosol and soot.

Spring variability of the parameter of aerosol condensation activity

This paper is devoted to the analysis of variability of thermo- and hygrooptical characteristics of atmospheric aerosol particles obtained at artificial moistening and heating of aerosol sample. The tendency of decreasing the parameter of condensation activity during spring has been revealed. The relation between hygro- and thermooptical parameters are considered. The estimates of condensation activity of different aerosol fractions have been performed.

Microphysical changes in the aerosol component of the gas-disperse mixture of near-ground air under the exposure to ultraviolet radiation (DRT-1000 lamp)

A gas-disperse mixture sampled from the near-ground atmosphere into a closed volume (1800 m3) of the Big Aerosol Chamber (BAC) was subjected to long irradiation by an ultraviolet lamp (DRT-1000). As a result of irradiation, the increased concentration of ozone was formed in BAC and the fine fraction of aerosol particles with the size r < 80 nm was intensely generated. In the course of the experiment, a spectronephelometer measured current values of the polarization components of the directed scattering coefficient β⊥,||(λi, θj). The time series of β⊥,||(λi, θj, tk) measured by the polarization nephelometer at four wavelengths λi = 455, 525, 585, 630 nm and five scattering angles θ j= 15, 45, 110, 135, 165° were used for numerical solution of the inverse problem of aerosol scattering. The evolution of the size spectrum of aerosol particles in the fine fraction with r < 200 nm has been traced.

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.

Long-term variability of aerosol and Black Carbon concentrations in the atmospheric surface layer as results of 20-year measurements at the IAO Aerosol Station

From the results of monitoring measurements at the Aerosol Station of IAO SB RAS in 1997-2016, the temporal dynamics of annual average aerosol concentrations was found to vary only slightly with an insignificant negative trend. The BC concentration demonstrates a stable tendency to decrease with a trend of -2.3% a year, which for 20 years has led to a total decrease in the imaginary part of the complex refractive index of the dry basis of particles from 0.062 to 0.044. The trends of variability of the aerosol and BC content for every season copy the dynamics of annual average values. The annual behavior of the aerosol and BC concentrations is characterized by a winter maximum and a summer minimum.

Seasonal variability of the aerosol absorption and scattering properties

An array of atmospheric aerosol optical characteristics is obtained from synchronous measurements on a long nearground path and in a local volume of air. The algorithm of statistical comparison of the data obtained is modernized. The spectral dependence of the single scattering albedo in the wavelength range 0.45 to 3.9 μm is calculated. Non-monotonic increase of albedo with wavelength is observed. Seasonal variations of albedo are estimated. Minimum values of albedo are observed in April and October, and maximum values are in July.

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.