T. B. Zhuravleva

Retrieval of aerosol optical and microphysical characteristics according to data of ground-based spectral measurements of direct and scattered solar radiation. Part 1. Testing of algorithm

The ground-based measurements of direct and scattered solar radiation to date serve as the most reliable source of information on the columnar optical and microphysical characteristics of atmospheric aerosols. We suggest an algorithm which combines the iteration retrieval of the optical single-scattering characteristics directly from the data of photometric measurements and the solution of the linear inverse problem which ensures the retrieval of the microstructure of homogeneous aerosol particles and complex refractive index of the aerosol material. Software, developed to make the routine experimental data processing more efficient, is described. Results of algorithm testing on different mono- and multi-component aerosol models are presented.

Simulation of solar radiative fluxes using altitude profiles of water vapor concentration, characteristic for conditions of Western Siberia

We present the results of simulating solar radiative fluxes at wavelengths of 0.2–5 μm in the clearsky atmosphere using regional models of the altitude distributions of temperature, pressure, and water vapor concentration, characteristic for summer (July) and winter (January) conditions of Western Siberia, and AFGL latitudinal meteorological models. The fluxes of upward and downward radiation, calculated with different altitude profiles of water vapor concentration for a constant value of atmospheric columnar moisture content, are compared. An electronic archive is created to increase the efficiency of massive radiation calculations; the archive contains the approximations of the transmission function of atmospheric gases by exponential series for a base set of the column water vapor content in the range of 0.5–3 g/cm2, using the HITRAN-2008 spectroscopic database.

Retrieval of aerosol optical and microphysical characteristics according to data from ground-based spectral measurements of direct and diffuse solar radiation. Part 2. Algorithm testing

We present the results of the study of sensitivity of our algorithm for retrieving the columnar aerosol optical and microphysical characteristics to measurement errors. The algorithm testing against data from field measurements under conditions of both increased and moderate aerosol turbidity of the clear sky atmosphere is discussed. We present the average values of the aerosol optical and microphysical characteristics retrieved according to data from photometric measurements at the AERONET station in Tomsk during 2004–2009 for situations when the aerosol optical depth in the spectral channel of 440 nm did not exceed 0.4.

Simulation of solar radiative fluxes in the atmosphere using different models of water vapor continuum absorption in typical conditions of Western Siberia

Total, direct, and diffuse solar radiation fluxes are calculated in the 0.2–5 μm spectral region in the cloudless atmosphere under typical winter and summer conditions of Western Siberia. It is shown that the CAVIAR continuum absorption model based on new experimental data provides for a higher sensitivity of the simulated fluxes to the total water vapor content than the MT_CKD model widely used in the radiative calculations. It is caused by the fact that the water vapor continuum in the CAVIAR data exceeds the MT_CKD prediction on average by an order of magnitude in atmospheric windows of the near IR spectral region.

Estimation of aerosol absorption under summer conditions of Western Siberia from sun photometer data

We tested the methods for retrieving the aerosol single scattering albedo and scattering phase function (asymmetry factor), developed by the authors earlier, from measurements of clear-sky radiance in the solar almucantar at the Tomsk station of the AERONET photometric network in 2003–2009. It is shown that, under conditions of strong atmospheric turbidity (fires), the results obtained using the suggested approach and the Dubovik-King algorithm agree well. Under typical summer conditions of Western Siberia, the average single scattering albedo in the blue and green wavelength regions are ∼0.90–0.92 and close to those presented in the WCP and OPAC models for continental aerosol.

Photophoretic motion of soot aerosols in field of shortwave solar radiation

The results of a theoretical analysis of the photophoretic motion of soot particles in the field of solar radiation under the conditions of stationary atmosphere are presented. In the refined radiation block of the model, integral fluxes of solar radiation were calculated by the Monte Carlo method in the context of the approximation of a plane-parallel horizontally homogeneous atmosphere. An analysis of the obtained results again verifies the possibility of significant photophoretic exhibitions for soot aerosol particles in the stratosphere; solar photophoresis can be considered an efficient mechanism of the vertical transport of absorbing submicron particles up to heights of the middle stratosphere. Forces of solar photophoresis can compete with forces of gravity up to heights of 30–35 km for particles of submicron and micron sizes. At the same time, the estimations again demonstrated the low efficiency of radiometric photophoresis for weakly absorbing, dense, and strongly heat-conducting particles of the atmospheric aerosol.

Solar radiative fluxes in the clear-sky atmosphere of Western Siberia: A comparison of simulations with field measurements

We compare the calculations and measurements of downward solar radiative fluxes on the Earth’s surface, performed in the clear-sky atmosphere during summers of 2010–2012 in the background area of the boreal zone of Siberia (Tomsk). The comparison is performed taking into account the instrumental errors and uncertainties of determining the atmospheric characteristics. The aerosol optical characteristics were specified using data of ground-based photometric measurements, obtained at the Tomsk station of the AERONET network. It is shown that the relative differences between the model-based and experimental values of the fluxes of direct and total radiation, on average, do not exceed 1% and 3%, respectively.

Optimization of sequential code for simulation of solar radiative transfer in a vertically heterogeneous environment

This article belongs to the series of works aimed at improving computing capacity of radiation codes implementing the Monte Carlo statistical method. A short description is given of the main blocks of basic (FORTRAN version) and optimized (C version) codes designed for calculation of sky radiance in a vertically heterogeneous medium. We present the results of tests which were aimed at evaluating the performance of each of the codes under different conditions in numerical experiments. In the cases examined, the performance indicators of the optimized C code were higher as compared with the basic one. It is shown that differences in execution time of the codes are reduced by increasing the optical density of the atmosphere, and using more productive computers. The developed C code can serve as a basis for creating a high-performance radiation code.

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.

Influence of 3D cloud effects on spatial-angular characteristics of the reflected solar radiation field

Spatial-angular characteristics of reflected solar radiation in broken clouds are simulated in the spherical model of the atmosphere using statistical algorithms developed in the Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences. The patterns of formation of radiance fields of scattered radiation, caused by the finite cloud extents, mutual cloud shading, and radiation re-reflection by neighboring cloud elements are considered by the example of individual cloud realizations. It is shown that, for small and moderate cloud fractions, the specific features of the radiance field of reflected solar radiation are mainly determined by cloud localization relative to the viewing direction and direction “toward the Sun”.