Home – Home – Jornals – Atmospheric and Oceanic Optics 2013 number 11

Water vapor line broadening coefficients induced by carbon dioxide are important for different problems of atmospheric physics, astrophysics, and laser physics. Line widths of H₂O–CO₂ were computed by a semi-empirical method for rotational quantum numbers J from 0 till 20. The temperature dependence was investigated and the temperature exponents for every transition were calculated.

The CO₂ absorption is measured in the 8000 cm^–1 region, calculation of the absorption coefficient is performed using the asymptotic line wing shape theory with fitting to the experimental data. Calculated coefficient values agree well with the measured data. According to the line wing theory the absorption in the band wings is conditioned by the wings of the strong lines of the near band. Within the framework of the theory, experimental and calculated data on the CO₂ absorption coefficient in the wings of two bands in the 8000 cm^–1 region can provide the information about the line shape at frequency detunings corresponding to several tens of half-widths. The results obtained support the hypothesis that line shape parameters in the line wings related to the transitions with the same initial state appear to be close to each other. The expression of the spectral line shape at large frequency detunings may be useful for modeling the radiative transfer in the atmospheric windows of the planets with significant CO₂ content.

Results of calculation of the mean intensity and deviation from the rectilinear direction of propagation of the optical beam crossing a shock wave at the beginning of a path in a homogeneous medium are present. It is shown that the spatial inhomogeneity of the refractive index of air in the area occupied by a shock wave in the vicinity of a conical body moving with the supersonic speeds can cause focusing effect on a beam intersecting shock wave. Magnitude of angular displacements of a beam, crossing shock wave, depends only on the height above the Earth's surface at which the shock wave is formed. The impact of shock wave on a beam crossing it decreases with the height increase.

The results of synchronous optical and meteorological measurements of Fried's coherence length on Big solar vacuum telescope are presented. The decrease of this parameter in winter time was detected. Spectra of wind speed and temperature inhomogeneities at the time of Fried parameter measurements were investigated.

The paper analyzes structural functions of air temperature in the ground surface layer over an inhomogeneous surface. Three main types of structural functions are separated based on processing of experimental data. Parameterization models for these three types of structural functions are proposed in the shift range corresponding to the inertial range of turbulence. The frequency of occurrence of the separated types of structural functions in different seasons at the observation site over an urbanized territory is estimated.

The paper presents statistics of parameters entering into analytical equations for structural functions of air temperature in the ground surface layer over an inhomogeneous underlying surface. The main attention is paid to analysis of histograms of these parameters. A rather high degree of variability of the parameters is noticed, which is connected, in particular, with the observation site and with the height of installation of the measuring instrument. The relation between parameters of the structural functions and standard deviations of the wind velocity and air temperature is considered briefly.

An original method of acoustic sounding of the outer scale of dynamic turbulence is suggested in the paper. An adaptive algorithm, developed by the authors, was used for interpretation of results of acoustic sounding. The efficiency of the suggested method is confirmed by a comparison of the results obtained with the data available from the literature.

As an example of practical application of femtosecond systems in problems of remote sensing is a comparison of the emission spectra of green plant leaf irradiated by femtosecond (fs) and nanosecond (ns) lasers. The prospect of remote lidar studies of natural objects, using femtosecond laser systems, aimed at determination of their microelemental and molecular composition is shown.

The experimental results on investigation of the emission spectra of sea aerosol under action of femtosecond Ti:Sapphire laser pulses of 800 and 400 nm wavelengths are presented. It is shown that emission of a sodium line at 588.9 nm is observed during irradiation by the first harmonic of radiation, while fluorescence of the organic matters dissolved in sea water is excited by the second harmonic.

Using data of IR transmittance spectra of aerosol samples and data of measurements of surface aerosol optical characteristics at Zvenigorod Scientific Station, a statistical relation of the Hänel parameter of condensation activity to air relative humidity and essential chemical components of aerosol, such as sulphates, nitrates, and minerals in particles with diameters of 1–2 mm, is studied. The Hänel parameter of surface aerosol containing nitrates has been shown to decrease with the increase of the relative humidity of air. The increase in portion of nitrates in micron particles results, probably, in a few increase in the Hänel parameter. The presence of poorly soluble mineral particles in 2-mm fraction of aerosol results in the decrease in Hänel parameter. Values of the Hänel parameter characteristic for sulphate aerosol are, probably, concluded within 0.4–0.6. Seasonal changes in the Hänel parameter are caused in part by changes in chemical composition of aerosol.

A comparison of calculation and measurement results of downward solar radiation fluxes at the Earth's surface, made in the cloudless atmosphere in summer of 2010–2012, in the background area of the boreal zone of Siberia (Tomsk) is presented. The comparison is made taking into account instrumental accuracy and errors in determining the atmospheric characteristics. To set the aerosol optical characteristics, ground-based photometric measurements data, obtained at the Tomsk site of AERONET network were used. It is shown that the relative differences in the simulated and experimental values of the fluxes of direct and total radiation is on average less than 1% and 3%, respectively.

The paper presents the data of observations of solar UV-B and total radiation in Tomsk (56.5°N, 85.1°E) in 2003–2012. The total solar radiation was measured by Yanishevsky pyranometer M-115M. The UV-B radiation, using the UVB-1 pyranometer. The Brewer MKIV S/N 049 spectrophotometer was used for total ozone and spectral UV radiation observations. The measurements of solar UV-B radiation and total ozone during the emergence and development of the ozone negative anomaly in spring of 2011 are discussed. The results of the spectral measurements of UV-B, UV-A radiation and total ozone data obtained during the spring ozone anomaly in 2011 are compared with observations in the same period of 2010. The 2010 ozone and UV radiation data have been taken as the most similar to long-term averaged norm for comparison. In 2011, during the reported period, exceeded values of daily doses of UV-B radiation reached 40%, and 36% of erythemal radiation. It is shown that the main contribution to the change in the values of UV-B radiation was made by significant reduction in total ozone relative to long-term norms. It is also shown that for certain regions of the spectrum (290–325 nm), the influence of such factors as cloud cover and surface albedo could partially or fully compensate for the increase in UV radiation, caused a significant drop in total ozone.

This paper considers the computational model to calculate the field of sky brightness in the atmosphere, caused by a single-scattered solar radiation in the visible range of the spectrum. The numerical simulation model of homogeneous layers of the atmosphere with altitude distribution coefficients of molecular and aerosol scattering and absorption is used. The calculation is performed in three spectral bands R, G, B, comparable to human vision and photographic recording.