V. N. Uzhegov

Peculiarities of the diurnal dynamics of the aerosol optical depth of the atmosphere in the infrared wavelength range

An attempt of the physical interpretation of the formation of the diurnal behavior of the atmospheric aerosol optical depth in the infrared wavelength range is undertaken based on the data of a comprehensive experiment that includes spectral measurements of the atmospheric transparency in near-ground and inclined paths in the wavelength range Δλ = 0.44–1.06 µm and measurements of the turbulent heat flux. Two hypotheses are proposed for the explanation of the effect of the postmeridian decrease of the atmospheric aerosol optical depth.

Relation of anomalous atmospheric conditions to electric field variation

Aerosol influence on strength value of atmospheric electric field in near-ground layer, based on in-situ measurements data, has been analyzed. The peculiarities of electrooptical relations in haze and smoke haze, cased by forest fires in summer, and through aerosol accumulation in near-ground layer at temperature inversion occurrence in winter, have been studied. The reasons of the revealed differences in the influence of smoke haze of various origin on atmospheric electric field value have been discussed.

Correlation between variations of aerosol extinction of visible and IR radiation in the near-ground layer and atmospheric column

Statistical processing is performed for data sets obtained at the Tomsk site in 2003–2005 on the boundary-layer spectral extinction coefficient β(λ) and the bulk-atmospheric aerosol optical depth τ(λ) in the wavelength range λ = 0.44–4.0 μ m. It is found that the maximal correlation between variations in β(λ) and τ(λ) is observed in the 2003 set under conditions of increased smoke content. It is shown that this can be related to an increase in the variability range of the aerosol extinction of radiation along both boundary-layer and in the atmospheric column at the time of arrival of smoke formations at the observation site. The correlation coefficients ρβτ(λ) for the cleaner conditions of 2004 and 2005 are much lower. The calculated eigenvectors of the joint autocorrelation matrix {βi(λ), τi(λ)} showed that the decrease in correlation between variations in β(λ) and τ(λ) can be related to the process of particle transport out of the ground level by convective and turbulent flows. This leads to aerosol depletion in the ground level and accumulation in the atmospheric column. The inverse process related to aerosol sedimentation is also possible.

Estimates of a midge contribution to the extinction of optical radiation in background summer conditions of western Siberia

The first estimates of a midge contribution to extinction of optical radiation for background summer conditions of Western Siberia are received. The radiation extinction coefficient due to midges (RECM), found from experimental data at a wavelength of 1.06 μm, changes from 0 to 0.14 km–1. An estimate of the mean RECM value in visible and infrared regions is 0.07 km–1. It is shown that the relative contribution of midges to the extinction coefficient of optical radiation in the 0.5–16 μm band is significant and varies on average from 26 to 63%.

Medium-size surface aerosols during winter-spring transitions

The variability of medium-size surface aerosol particles with radii of 0.3–0.6 μm during winter-spring transitions is studied in the experiments carried out at the Aerosol monitoring station of the Laboratory of Aerosol Optics of the Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences in 2009–2013. Time variations in the aerosol extinction coefficient in the spectral range 0.50–3.9 μm measured along a surface horizontal path is analyzed, as well as the size distribution function in the range 0.2–5.0 μm measured using a PKGTA photoelectric counter at one end of the path. A correlation between the variations in medium-size aerosol concentration and fine aerosol condensation activity is studied. The experimental spectral extinction coefficients are compared with those calculated by the Mie theory for the approximated size distributions.

Peculiarities of the diurnal dynamics of the aerosol optical thickness of the atmosphere in IR wavelength range and its physical interpretation

Analysis is carried out of the diurnal dynamics of the aerosol optical thickness of the atmosphere τA(λ) and the aerosol extinction coefficients in the near-ground layer α(λ) in the wavelength range λ = 0.44 - 1.06 μm, as well as of the vertical turbulent heat flux, measured simultaneously in June 2004 in the region of Tomsk. It is revealed that aerosol extinction in the near-ground layer in the range λ = 1.06 μm under conditions of small cloud fraction continuously increases during a day, but the aerosol optical thickness increases before 12-2 p.m., and then rapidly decreases. Probably, this fact is one of the factors of weak correlation between variations of the aerosol extinction of optical radiation on a near-ground path and in the atmospheric column. It is shown that the diurnal dynamics of τA(1.06) well correlates with the dynamics of the vertical turbulent heat flux.

The effect of fires on the intensity of electric field

Correlation of variations of the aerosol extinction coefficients of optical radiation and the intensity of electric field under haze and smoke conditions is analyzed on the basis of comprehensive field measurements. It is revealed that significant (almost by an order of magnitude) decrease of the intensity of electric field is observed in smoke, when increasing the atmospheric turbidity. It contradicts to the well-known electrooptical relationship and gives the reason to assume that the quantity of charged particles significantly increases in smoke that dramatically changes the manner of electroptical relations. At great number of fires on the Earth, one should take into account this fact in climatic models and to remember it when considering the physical mechanisms of the effect of solar activity on weather and climate.