Home – Home – Jornals – Atmospheric and Oceanic Optics 2013 number 1

This paper considers the propagation of pulsed optical Gaussian beams through a homogeneous medium under different diffraction conditions on a transmitting aperture. It is shown that for any curvature radius of the initial wave front the diffraction broadening of a pulsed beam decreases with a decrease in the pulse duration, and in the limiting case of zero pulse duration the diffraction spreading of a pulsed beam is absent.

The single (axial) filamentation regime of high-power collimated femtosecond laser radiation in the atmosphere is theoretically investigated. The effect of laser beam initial diameter on characteristics of a filament is analyzed. We consider three filament parameters: the coordinate of the filament beginning, its length and longitudinal continuity. We found that for the same initial beam power all the above characteristics of filaments show the dependence on the beam radius. As the main physical cause for this circumstance the diffraction interaction of various beam areas during the filamentation process is considered; the strength of this interaction increases as the beam widens.

Line shape data for different СО₂ and H₂O bands are retrieved by fitting to the available in literature experimental data on the respected continuum absorption. The obtained line shape strongly depends on spectral region, which is consistent with the main principles of the asymptotic line shape theory.

By data of a network of posts for greenhouse gases monitoring at West Siberia area the distribution of carbon dioxide is analyzed at the passage of frontal sections. To except the influence of meteorological parameters, all initial data were pre-reduced to standard conditions. It was found that in the cold season the CO₂ concentration increases in the cold front rear and decreases behind the line of the warm front. In the warm season, due to augmentation of the plant vegetation, which in this period is both the source and drain of the carbonic gas, its distribution becomes opposite to the observable in the cold period. In transition periods, both summer and winter variants of CO₂ distribution in zones of fronts are possible, which depends on the prehistory of the air mass, coming to the region.

This is the third in a series of papers devoted to the development of technical tools and techniques for rapid and comprehensive analysis of the ecological status of coastal waters by optical methods. The possibility of shore-based optical systems to map and to determine the dynamic characteristics of ocean eddies and internal waves are shown. The efficiency of the maximum cross-correlation method to recover the velocity field of the flow in the vortex body and the phase velocities of internal waves, using optical images of the sea surface is discussed.

The technical means for the real time control for phytoplankton by fluorescence method in coastal waters are considered. Preliminary results of the monitoring by the immersion fluorometric system for the real time measurements are given. The article discusses the possibility of using fiber optic immersible and pumped systems for integrated monitoring of coastal waters.

Relative concentration of ¹³CH₄, ¹²CH₄ and ¹³CO₂, ¹²CO₂ in the atmosphere contains information about carbon dioxide and methane emission sources. High resolution of modern ground-based IR Fourier spectrometers allows one to resolve absorption lines of different isotopologues of the trace gases in atmospheric transmittance spectra. The modeling of synthetic atmospheric transmittance spectra within 2200–11000 cm^–1 spectral region has been done and good signals of ¹³CH₄ and ¹³CO₂ were found. Several atmospheric transmittance spectra measured with ground-based FTIR at the Ural Atmospheric Station in Kourovka and at the Institute of Environmental Physics of Bremen University during 2010–2011 have been selected and processed. This paper presents a method and first results on the remote sensing of ¹³CH₄/¹²CH₄(δ¹³C_CH4) and ¹³CO₂/¹²CO₂(δ¹³C_CO2) in the atmoshpere.

The project of the eye-safe High Spectral Resolution Lidar with a wavelength of 532 nm is proposed. Absolute calibration is provided by the molecular channel with iodine cell cavity for filtration of the aerosol signal. Transmitter has a laser beam expansion via receiving telescope to have a design with high thermo-mechanical stability to install small field-of-view and substantially reduce background sky noise. A detailed optical diagram of the transceiver is provided by the transmitter and receiver located on different sides of the optical bench. Characteristics of the laser and the system are given. Calculated lidar returns and errors of measurements are estimated. To have ten percent accuracy in troposphere, the aerosol backscattering and optical depth time of averaging should be from ten seconds to one minute. Proposed system must run continuously and be unattended.

Specular reflection is a bright spot of intensity observed when light is reflected by cirrus clouds, snow blankets, and wavy water surfaces. The analytical expressions, which combine specular scattering on particulate media and rough surfaces, are obtained. The conditions, which allow the identification of the scattering media from the differential cross-section, have been determined for remote sensing applications.

The experimental results on remote detection of vapor of a number of chemical compounds in the atmosphere using the Raman lidar system with the narrow line eximer KrF laser and multichannel spectrum analyzer, based on diffraction spectrograph and intensified CCD camera, are presented. The sensitivity evaluation of the system with sensing range 6–10 m is given. Using additional suppression of the intense Raman bands of the molecules N₂ and O₂ the threshold of detection of 1 ppm is reached. The experimentally registered bands of the overtones of oxygen and nitrogen in the Raman spectrum of the atmosphere are demonstrated. The absence of the fluorescence and the Raman signals overlapping is confirmed experimentally.

The paper examines the response of the upper atmosphere parameters to the unique geomagnetic storm on January 21, 2005 at middle latitudes. Measurement data of the OI 630 and OI 557.7 nm airglow intensities, the magnetospheric pulsations and ionospheric parameter variations obtained for the Eastern Siberia region (52 N, 103 E) are used for the analysis. Penetration of the global electric field into middle latitudes, geomagnetic pulsations with periods ranging from 0.2 to 1000 s, radio wave absorption in the D ionospheric region, the occurrence of sporadic auroral-type Es formations at altitudes of 140–200 km, and an increase in the intensity of the atmospheric 630 and 557.7 nm emission were observed during this storm. It has been suggested that, in this case, the disturbance of the mid-latitude upper atmosphere parameters might have been resulted from precipitations of energetic charged particles into the ionosphere. These precipitations took place during magnetosphere compression under the influence of enhanced dynamic pressure of the solar wind.

The features of application the low-angle laser light scattering method for study of the pulse formation of aerosol media are discussed. A modification of the measuring system, which allows the study of a cloud simulated in the laboratory conditions, almost from the time after its formation was proposed.

In atmospheric pressure air formation and decay of diffuse "channels" of corona discharge, as well as optical and X-ray radiation were investigated. Modulate pulses (~ 290 kHz) of high voltage (~ 250 kV) with duration of 10 ms was used. A soft X-ray radiation was obtained from corona discharge. In the area of diffuse “channel” and at a distance from the plasma channel the bright glowing points was registred. It was determined that on diffuse “channels” bends appear, the length of which is increased by the end of the pulse voltage