Vol 31, No 1 (2018)

The solar radiative fluxes in cloudy and cloudless atmospheres are calculated taking into account multiple scattering and absorption. The cloudy conditions observed in Tomsk and Volgograd regions are considered. A comparison between the fluxes calculated using different models of water vapor continuum absorption, such as the MT_CKD empirical model, commonly used in the atmospheric simulation, and the continuum model based on the CAVIAR experimental data, is carried out. The impact of the water vapor continuum on the shortwave radiative fluxes in the presence of different cloud types is estimated.

The variations in the optical-microphysical properties of the mixed wood smoke are studied in the Large Aerosol Chamber, Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (volume of 1800 m³) during long-term (6-day) smoke aging under the conditions of periodic impacts of relative air humidity varying in the range 45–95%. Spectral nephelometric measurements of angular scattering and solution of the inverse problem were used to analyze the dynamics of the size distributions and complex refractive indices for ultrafine, medium-sized, and coarse fractions of particles, as well as effective particle radius, lidar scattering parameter, and single scattering albedo in the visible spectral range. It is found that both quantitative and qualitative features of the variations in the aerosol optical-microphysical parameters substantially change at different smoke aging stages as functions of air humidity. It is shown that, during aging of the mixed smoke, the key factors of the variations in smoke properties are the physical-chemical heterogeneity of three fractions of smoke particles, as well as the physical processes of coagulation migration of ultrafine black carbon particles (<100 nm in size) across the size spectrum and the condensational wetting of smoke particles. The interrelated effect (“interference”) of these processes on the particle structure determines the main features of the dynamics of the disperse composition and absorption properties of smoke particles.

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 ≤ τ_smoke(0.55 μm) ≤ 4.

The formation and propagation of postfilamentation channels along a controllable path 150 m long are studied experimentally for collimated beams of different diameters. During multiple filamentation, a laser beam is compressed into a global focus, after passing which its angular divergence is much greater than the divergence of postfilamentation channels generated during the filamentation. It is shown that the intensity of the postfilamentation channels is sufficient for starting multiple filamentation in optical elements at distances much longer than the filamentation region length.

For the background region of Tom–Ob interfluve, we performed the comparative analysis of the chemical composition of water- and acid-soluble aerosol fractions in dry deposits, coupled with an estimation of the ratio of submicron and coarse fractions in near-ground aerosol in this background region, and a study of their mineral and material composition using scanning electron microscopy. Differences in the ratios of metals between the water- and acid-soluble fractions are revealed. It is reasonably hypothesized that water- (acid-) soluble compounds are mainly contained in the submicron (coarse) fraction.

A passive optical method for measurements of the average crosswind speed on the atmospheric path has been developed. The crosswind speed estimation is based on the correlation algorithm for measuring fluctuations of the energy centroids of images of topographic objects under natural daylight. Test results of a windspeed- meter prototype, constructed based on this principle, are described. The wind velocity assessments recorded by this passive optical meter and an acoustic weather station are compared. The optimal time of accumulation of the cross-correlation function is estimated, which ensures stable real-time wind measurements.

A new algorithm for retrieving the total content of atmospheric fine particulate matter (FPM) (particles with a size of less than 1.0 and 2.5 μm) from multispectral satellite images in visible and IR regions of the electromagnetic spectrum is described. The algorithm is based on the regression relations between the top of atmosphere (TOA) reflectance, microphysical parameters of aerosol, and geometrical parameters of the satellite scene. The regression equations are built based on the calculated TOA brightness in the spectral channels of the satellite instrument for the ensemble of randomly generated parameters of the atmospheric radiative transfer model and geometrical parameters of the satellite scenes. Subsequently, this allows real-time mapping of the atmospheric FPM pollution directly from the satellite images without solving ill-posed inverse problems based on the solar radiation transfer in the atmosphere and aerosol light scattering. The algorithm suggested is implemented and tested for the MERIS (Medium Resolution Imaging Spectrometer) satellite instrument. Comparison of the MERIS-retrieved total content of the atmospheric FPM with AERONET (Aerosol Robotic Network) data shows a standard deviation of ~0.5 μg/cm². The applicability of the algorithm developed to real-time monitoring of the regional and transboundary transport of the atmospheric FPM pollutants during wildfires is demonstrated.

The applicability of the Levenberg–Marquardt method, modified for the case of inaccessibility of a priori covariance matrices for methane vertical profiles, to atmospheric methane total column retrieval from the spectra measured by METOP/IASI is studied. The method and algorithm are software implemented together with an iterative evaluation of a posteriori covariance matrices and averaging kernels for each individual case of retrieval. This allows selection of the results based on properties of both matrices. The comparison between our results and IASI standard methane products retrieved from the same spectra shows their satisfactory agreement.

Nanosecond discharges in air, SF₆, and helium at pressures of units–tens of Torr are studied. Spatial inhomogeneities of diffuse jets and autographs of runaway electron (RAE) beams are recorded in all three gases during a discharge in a nonuniform electric field. It is shown that diffuse jets change their shape and their lengths increase and change from pulse to pulse in the discharge gap as the pressure decreases; further, it is confirmed that the RAE beam amplitude increases as the gas pressure decreases. It is assumed that inhomogeneities observed in the diffuse jets and RAE beams can be associated with transient luminous events in the Earth’s atmosphere that have sizes of tens of kilometers and occur at high altitudes at low pressures under high thunderstorm activity.