Home – Home – Jornals – Atmospheric and Oceanic Optics 2015 number 10

The water vapour continuum absorption (or continuum) has a special importance for radiation balance of the Earth. In this paper one of the poorly studied spectral regions of the continuum absorption 8500-12500 cm ^-1 (1.17-0.8 μm) is investigated, focusing on two absorption bands of water vapour. The continuum was derived from experimental pure water vapour absorption spectra obtained using a high resolution Fourier transform spectrometer. Measurements were carried out at elevated temperatures (from 398 to 471 K) and pressures (from 1 to 5 atm). Well-pronounced spectral absorption peaks were found within absorption bands, that are absent in the widely used MT_CKD model. Estimation of the total dimerization equilibrium constant for stable and metastable dimers, derived by fitting a simulated water dimer spectrum to the experimental continuum at 400 K, amounted of 0.028 atm ^-1, which is twice higher than the modern ab initio prediction of this value.

Aerosol mass concentration variations in a smoky atmosphere of Moscow region in autumn 2014 have been analyzed. The soot mass fraction and ratio between aerosol mass concentrations PM-2.5 and PM-10 were typical of the fires in boreal forests. Smoke screening of the Moscow region was due to long-range transfer of the smoke aerosol, that was confirmed by a joint analysis of aerospace monitoring data and inverse trajectories of air mass transfer, and local fires in Moscow region. As the result, statistical characteristic variations of the smoke aerosol mass concentrations, including empirical probability distributions and power spectra, turned to be non-typical.

The annual behavior of concentration of an organic component of the atmospheric aerosol which is selected from a board of the Tu-134 “Optic” airplane-laboratory in the atmospheric layer of 500-8500 m is investigated. It is revealed that the greatest concentration of the organic components as a part of the aerosol is observed in spring, the smallest, in the fall. As a part of aerosol particles compounds from C ₈H ₁₈ to C ₃₅H ₇₂ are found. The range is widest during the winter period (C ₁₂H ₂₆-C ₃₅H ₇₂) and in spring (C ₈H ₁₈-C ₃₁H ₆₄). In the summer (C ₁₈H ₃₈-C ₃₃H ₆₈) and in the fall (C ₁₆H ₃₄-C ₃₁H ₆₄) it is noticeably narrower. During the whole year as a part of an aerosol one mode (n-alkane C ₂₀H ₄₂) dominates. During the summer period there is a secondary maximum, falling on the n-alkane C ₂₉H ₆₀.

The influence of the upper limit λ _max of the spectral range, in which atmospheric transmission measurements are performed, on retrieving aerosol microstructure parameters is investigated. Aerosol microstructure parameters are determined by solving the inverse sun photometry problem using data of numerical simulation and field experiments. The aerosol model formed by fine ( f ) and coarse ( c ) particle fractions is used in the numerical experiment. The value of λ _max is chosen in the range from 1.052 to 3.973 mm. The method of integral distributions is used for solving the inverse problem. It is shown that the contribution of large particles to the total aerosol distribution is underestimated. In particular, at λ _max = 1.246 μm, the losses in the retrieval of concentration of c-particle fraction can achieve 42% against the 18% decrease in the aerosol volume concentration.

The results of numerical statistical simulations of experiments of the cloud layer ground-based sensing by the terahertz linearly polarized radiation at few wavelengths from the atmospheric transparency windows are presented in the paper. Liquid droplet size distributions, summarized results of many years field measurements in the midlatitudes of the Earth and the distributions obtained by aircraft experiments off Great Britain coast are used in the scattering layer models. The models of the scattering medium take into account the vertical stratification of the water vapor concentration in the atmosphere and the differences in the cloud layer microstructure at the top and base.

Possibility of determination of the turbulent energy dissipation rate from data measured by a 1.5-μm pulsed coherent Doppler lidar using the conical scanning of the probing beam under different atmospheric conditions has been studied experimentally. It is shown that from array of the radial velocities measured by this lidar in the atmospheric surface layer during 5 min one can estimate the dissipation rate with the relative error 20-30% under conditions of moderate and strong wind turbulence.

Dynamics of the air temperature in the lower 4 km layer have been studied by the data of radio-sounding in Dolgoprudny and ground meteorological measurements at Moscow University in time of anomalous heat wave in summer of 2010. The results have been compared with the aero-climatic data during previous 19 years. Accordingly to these data average estimations of both the daily vertical thermal gradient values, thickness, and intensity of nocturnal surface inversions (correspondingly, 200-300 m and 2.0°С) are presented for Moscow region. As it shown, in summer of 2010 in the air layer up to 2 km height over Moscow record high air temperature was noted for the period from at least 1991. Among others, the 30°С value has been detected for the first time in the air layer from 400 to 800 m. During heat wave in 2010, as a result of clear anticyclone conditions, thickness, and intensity of nocturnal surface inversions were larger than usually (up to 700 m and 12°С correspondingly). The mean temperature profiles have been studied for different types of air masses. As it shown, the tropical air mass dominated over Moscow region in summer of 2010 during more than half of the time.

The paper represents the results of the correlation analysis of observation series of total ozone and ultraviolet radiation in 300-315 nm wavelength band for temperate zone stations of Russia and Canada (Northern hemisphere, 50 N and higher) in the boreal forest zones. It is shown that the ozonosphere is the primary modulator of the biologically active UV-B radiation spectrum part in this climatic zone. Radiation amplification factors of solar UV-B spectral region are determined. It is demonstrated that 20% of total ozone depletion leads to the increase of the dose of the shortwave part of solar UV-B radiation more than twice relative to its climatic norm.

Metrological support for production and exploitation of ultrasonic (anemometers/thermometers) thermoanemometers (UTA) for measurement of meteorological parameters of the atmospheric boundary layer is considered in this article. Necessary types of UTA test: in zero wind chamber, air tunnel, climatic chamber, pressure chamber are represented. Parameters of the air tunnel ADS-60, which was created in IMCES SB RAS, are described. ADS-60 is designed for testing UTA against rules of Russian Federal Service for Hydrometeorology and Environmental Monitoring for wind velocity. Mobile complex of check technical parameters of UTA in field conditions is represented.

In order to reduce the effect of time delay on the work of the adaptive system as a dynamic feedback system, a modern approach to the correction of turbulent distortions of optical radiation involves the use of new control algorithms for correcting mirror using prediction of phase distortion. Here the results of numerical simulation are presented.

The problem of second harmonics generation (SHG) of monochromatic spatially coherent paraxial radiation in homogeneous quadratic nonlinear uniaxial crystals is considered theoretically. It is assumed that the laser radiation is focused into a crystal by two crossed cylindrical lenses with different focal lengths. The aim of this study is to find dependences of optical focusing parameters on the primary radiation power. The work consists of two parts. Part 1 describes the mathematical apparatus required for the study. It is suggested to transform a set of nonlinear wave equations to a form, more convenient for further use. Some important particular cases are considered. An asymptotically exact analytical solution of the SHG problem is presented.

The problem of second harmonics generation (SHG) of monochromatic spatially coherent paraxial radiation in homogeneous quadratic nonlinear uniaxial crystals is considered theoretically. It is assumed that the laser radiation is focused into a crystal by two crossed cylindrical lenses with different focal lengths. The aim of this study is to find dependences of optical focusing parameters on the primary radiation power. The work consists of two parts. Part 2 presents main results of numerical calculations. It is shown that optimal focusing parameters first vary insignificantly as the primary radiation power increases. Then, beginning from a certain power value, which depends on the initial conditions of the problem, the SHG efficiency maximum becomes attainable at weaker and weaker focusing, and the value of the efficiency maximum monotone increases, probably tending to a value close to 100% under an infinite increase in the power.