T. Yu. Chesnokova

Sensitivity of downward long-wave radiative fluxes to water vapor continuum absorption

An analysis of modern models of water vapor continuum absorption is presented. The sensitivity of downward long-wave fluxes to water vapor continuum absorption is investigated. The spectral intervals where continuum absorption is the most significant are defined. Recently discovered discrepancies between the model and experimentally measured absorption coefficients in the atmospheric transparency window of 8–12 μm are analyzed. It is shown that these discrepancies do not influence on calculation of long-wave radiative fluxes for the temperature range achievable in the Earth’s atmosphere.

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.

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.

Spectroscopic factors, influencing the accuracy of the atmospheric radiative transfer simulation in the methane absorption bands in the near infrared region

The analysis of basic spectroscopic factors influencing the simulation of atmospheric radiative transfer in the methane absorption IR bands, which are used in the problems of methane total content retrieval from atmospheric solar spectra measurements, is carried out. The role of uncertainties in the parameters of methane and water vapor absorption lines and differences in extraterrestrial solar spectrum models are considered. The comparison with measured atmospheric spectra is made.

Influence of the overlapping of the atmospheric gas absorption spectra on the retrieval of the total methane content in the atmosphere from the transmission in the 1.6 to 1.7 μm spectral region

The influence of the spectral lines of atmospheric gases on the retrieval of the methane concentration from the measurement of the solar radiation spectrum in the spectral region of 1.6–1.7 μm is studied. The modeling of the atmospheric transmission function for different vertical profiles of the methane and ethylene concentration in this range has shown the necessity of taking into account the ethylene spectral absorption lines in radiation calculations in this range in addition to the CH4, H2O, and CO2 usually taken into account.

Parameters of broadening of water molecule absorption lines by argon derived using different line profile models

The water vapor absorption spectrum was measured in the spectral region 6700–7650 cm–1 with argon as a buffer gas. The room-temperature spectrum was measured using a Bruker IFS 125-HR Fourier Transform Spectrometer with high signal-to-noise ratio, with a spectral resolution of 0.01 cm–1, at argon pressures from 0 to 0.9 atm. The H2O absorption spectral line parameters are derived by fitting two line shape profiles (Voigt and speed-dependent Voigt) to the experimental spectrum. It is shown that the use of speed-dependent Voigt profile provides the best agreement with experimental data.

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.

Total water vapor content retrieval from sun photometer data

Simulation of Sun photometer measurements for two regions of Russia is made and total water vapor content retrieval errors, caused by variations in meteorological parameters and the application of empirical formulas used in AERONET, are estimated.

Atmospheric radiation distributed information-computational system

The Atmospheric Radiation Internet-accessible distributed information-computational system is described. The system’s servers are located at the Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (Tomsk); Volgograd State University; and Ural State University (Yekaterinburg). The information-computational system not only provides for access to data, but also allows for the calculation of the radiative characteristics of the Earth’s atmosphere. The system is aimed at investigations of the radiative transfer in the Earth’s atmosphere. The radiative models of the system are interesting for postgraduate students, students, and specialists in the area of atmospheric radiation and climate.

Retrieval of content of greenhouse gases from atmospheric spectra of solar radiation with the use of different spectroscopic data on absorption lines

Atmospheric spectra of solar radiation, calculated with different data on absorption lines of atmospheric gases are compared with spectra measured with a ground-based high-resolution Fourier-transform spectrometer. The contents of carbon dioxide and methane in the atmospheric column are retrieved from measured spectra with the use of different modern spectroscopic databanks in the direct problem. Values of the methane content in the atmosphere retrieved with the use of two last HITRAN versions are shown to differ almost by 2%; a lower difference was observed for carbon dioxide.