Home – Home – Jornals – Atmospheric and Oceanic Optics 2013 number 9

Simulation of the atmospheric transmission, using spectral line parameters from HITRAN-2008 database and CDSD databank, and the approximation of CO₂ absorption line profile, taking the line-mixing effect of closely spaced lines into account, are carried out. For CO₂ it is shown the characteristic examples of the spectral regions, where contribution of the effect is recommended to be taken into account in calculation of transmission in the atmospheric conditions.

The results of numerical simulation of the nonlinear propagation of high-power pulsed laser radiation at a wavelength of 10.6 microns in air upon Kerr self-focusing and filamentation are presented. The optical model of air involves cubic and higher optical nonlinearity, plasma nonlinear absorption and refraction, and air linear absorption. The single-filamentation regime of the laser pulse with peak power of up to few terawatts and pulse duration of one picosecond is studied. For the first time we show that in contrast to the filamentation in the near-infrared wavelength range, the specific feature of long wavelength radiation self-action in air is the formation of abnormally elongated and wide intense light channel followed by nearly continuous along the propagation direction plasma column. The peak electron density of the formed plasma column is comparable to that created by a femtosecond radiation in the near-infrared spectral range. The physical cause for these peculiarities is the change of air ionization regime by picosecond CO₂-laser pulses in favor of bound electrons tunneling through the atomic potential barrier and the progressive development of the electron avalanche.

The results of laboratory experiments on nonlinear propagation of intense pulse-periodic and continuous wave CO₂ laser radiation in a gas medium are presented. Experiments were carried out in a cell containing a mixture of air and carbon dioxide at different partial concentrations (~ 1–10%), in the conditions of strong absorption and thermal blooming of laser radiation. The experimental conditions simulated the atmospheric propagation of intense laser radiation at a kilometer-length path. Sharply focused laser beams were used, and the areas of heat release along the beam channel were registered by the shadow imaging method. We found that the focal waist of the laser beam is characterized by the reduced heat release as compared with that in the pre- and post-focal beam regions. The most probable cause of this circumstance is considered to be the resonance absorption saturation of CO₂ molecules, which becomes apparent at high intensities in a laser pulse (a “path cleaning” effect). For continuous wave radiation, this effect appears in a lesser extent.

The analysis of mechanisms of radiation scattered in the range of angles θ from 0 to 180° is made for a sphere by comparing the exact phase scattering functions calculated with the Mie theory and interference phase scattering functions with the use of diffraction and partial rays of geometric optics (GO). In view of refinements of relative phase shifts of all rays and the amplitude of the diffraction ray, it appeared that large-scale oscillation regularities of the exact phase scattering function at high Mie parameters x corresponded to the interference pattern of two or three rays mentioned above. For integral characteristics a computation error with the interference formulae in the range of angles θ = 0 ÷ 10° does not exceed units of percent for х > 10 and within the large x values it tends to zero. For other ranges, depending on the difference in the combination of the integer parts parity in the p intervals of the total scattering angle tendency of oscillation periods over the angle to zero is seen according to the laws of х^–1, х^–2/3 (rainbows) and х^–1/2. The oscillation period over x begins to depend only on θ. The results of the calculations of exact phase scattering functions average over the intervals Δθ = 10 ÷ 15° for the refraction index m = 4/3 are presented in the form of approximation relationships with the asymptotic tendency to the GO phase scattering function.

Artificial radio nuclides, such as iodine-131 (¹³¹I), cesium-134 (¹³⁴Cs) and cesium-137 (¹³⁷Cs), as well as natural isotopes of beryllium-7 (⁷Be) and potassium-40 (⁴⁰K) have been registered in atmospheric aerosols over Vladivostok selected from 11 March to June 17, 2011. Artificial radio nuclides were also discovered in atmospheric wet depositions. Variability of gamma activity of natural isotopes of ⁷Be and ⁴⁰K is not greater than one order of magnitude throughout the sampling period. Synoptic analysis of back trajectories movement of air masses showed that the radioactive cloud came from the regions of Siberia and North-Eastern part of China.

The adsorption and photosorption properties of precipitated aerosol produced by dispersing mineral magnesite crystal, MgCO₃, under ambient air were investigated. Analysis are carried out of the texture of precipitated aerosols sample, the crystal structure and the adsorption layer composition of micro particles formed by grinding of crystal under ambient air. The kinetics of desorption and photodesorption of CO₂ from micro particle surfaces and the interaction of Freon 22 (CHF₂Cl), CO, O₂, and N₂O with its surfaces under darkness and illumination were studied. The quantum yields and their spectral dependencies for CO₂ photodesorption and O₂ photoadsorption were determined. It is shown that magnesite mineral aerosol is active under illumination for removal of oxygen containing electron-acceptor gases from Earth’s atmosphere.

Passive sampling is a simple low-cost method for assessment of concentrations of gases in air. In comparison with standard methods, the precision of the results of passive sampling measurements is more influenced by meteorological and methodological factors. Results of theoretical and experimental studies of a number of factors, which influence the precision of the results of passive sampling measurements of ambient NO₂ are presented. Comparison of passive sampling method and reference methods (sorption tubes, chemiluminescent gas analyzer) under moderate continental climate conditions demonstrated systematical statistically significant underestimation of concentrations, measured by passive samplers method. It was shown that the difference observed is accounted for the drawbacks of the model commonly used for treatment of passive sampling data; the model does not take into account particularities of interaction between NO₂ and sorbent solution that are related to the influence of relative humidity. A new NO₂ passive sampling model based on available data on interaction between NO₂ and a sorbent solution was developed. Application of the model allowed us to improve agreement between NO₂ concentrations calculated from passive sampling data and those measured by reference methods, to eliminate systematical and statistically significant difference between the datasets.

The characteristic times of photoionization of the ground 3S level and excited 3P one of the sodium atom are calculated. The model of the balance equations of the ionization and recombination kinetics was constructed for optically thin case, based on the experimental scheme of reactions of the complex ion formation with participation of sodium, which considers also photoprocesses for the basic and excited levels. The numerical solution of the balance equations gives the time behavior of the sodium atomic density, ionic density, and complex ionic density when taking into account the laser illumination of the resonant transition at a wavelength of 0.589 μm.

A comparison of the vertical profiles concentrations of O₃, CO, CO₂, and CH₄ measured with the help of flying laboratory Tu-134 “Optic” (SML) and recovered according to the instrument IASI satellite MetOP is performed. The comparison showed that the absolute difference between the concentration of ozone SML – IASI may vary from 3 to 18 ppb, at a height of 0.5 km and from –8 to –38 ppb 7 km. The relative differences are in the range of 8–30% at 0.5 km and 12–88% at 7 km. For profiles of CO an absolute difference between the concentration of CO SML – IASI can vary from 32 to 103 ppb at an altitude of 0.5 km and from –18 to 23 ppb at 3 km. The relative difference are in the range –4–48% at 0.5 km and –8–20% at 7 km. Maximum difference of methane profiles in the boundary layer reaches 150 ppb, and the minimal one –10 ppb. The average relative difference varies from +2.8 to –0.5%. Maximal and minimal profiles for all flights are in range from 7.8 to 1.2%. Minimum, from –0.4 to –3.4%. The average difference between SML – IASI is in the range ±1.5 ppm, while the individual profiles are not comparable. The maximum and minimum differences for all flights are high, namely, in the atmospheric boundary layer 10 and –12 ppm, respectively. The maximum and minimum relative deviations for all flights are +2.3 and –3.3% in the boundary layer, respectively. Above the boundary layer relative deviations are reduced to ±1.0%.

The paper analyzes the influence of the winter stratospheric warming (SW) on the characteristics of the vertical distribution of temperature and density of the air in the middle atmosphere above Tomsk. The sudden SW in winters 2009/10, 2010/11, and 2011/12 and summers of 2010–2012 with a stable vertical temperature distribution were considered. It is shown that for disturbed conditions caused by the winter warming, the deviation of temperature and density of air from the mean values are in opposition and have expressed mirror symmetry with respect to zero. Their maximum amplitude occurs at 35 to 40 km and can reach +30% for the temperature and –30% for the density. Under quiet conditions in the summer months, the temperature deviation is in the main range –6 ¸ +8%, and the density of the air, –8 ¸ +15%.

The problem of ecological conditions at Norilsk industrial area is discussed. The NASA database on OMI sensor (AURA satellite) is used for 2004–2012 years. The largest share of sulfur dioxide emissions were detected in January–May and November (90%). The maximum emission of 95 kt per month was observed in November 2004. A comparative analysis of data from the satellite with ground-based environmental monitoring and airborne monitoring data was carried out. The space and ground-based data differs by 30–65%, the space and airborne data – by 14%.

We analyzed the existing software for atmospheric correction of satellite data in the channels of the visible range, their advantages and disadvantages. The architecture of software complex, developed at Institute of Atmospheric Optics for atmospheric correction of satellite measurements, is presented. We consider the application of algorithms for the purpose of constructing the cloud mask and removing the semitransparent clouds by the example of satellite images of ETM+/Landsat-7 instrument.

The main theoretical relations, necessary for the method of the measurement of the turbulence characteristics from the flutter of the astronomical imades on the board of the flying plane, are presented. The monostatical and differential (the bistatical) receivers are consequently compared. The analysis does not repeat the analysis of signals and errors of the traditional differential method. The method, proposed by us, supposes the operation with moving carrier. It is shown that maximum deviation of the bistatical response function from the monostatic ones exists when the velocity vectors of the carrier and the carrying channel are collinear. The influence of the turbulence outer scale, of the velocity vector of the carrier, frequencies of taking countings out, and other parameters of the meter scheme are estimated. In particular, it is found that typical correlation time in the bistatical differential receiver depends on the time of the carrying of the inhomogeneities between two receiving channels until the distance between them is less than the turbulence outer scale.

This paper presents the emission spectra of the most powerful in the present LEDs in the visible range of the spectrum (by comparison with the emission spectrum of halogen lamp), which can be used as a transmitter in the Fourier transform spectrometer instead of halogen bulbs. It is concluded that it is possiblie to obtain registration sensitivity to 10^–8 cm^–1 for the absorption coefficient in the visible range when using LEDs. The registration of the absorption of water vapor in range 15400–16200 cm^–1 showed the validity of the conclusions.