Showing papers in "Atmospheric and Oceanic Optics in 2013"
TL;DR: The SP-9 and SPM multiwavelength sun photometers are described and briefly characterized in this article, and the SPM portable photometer is designed for the air transparency measurements in mobile conditions, including a solar sensor, an automatic sun pointing/tracking system, a built-in GPS detector, a flash drive, and sensors for meteorological parameters.
Abstract: SP-9 and SPM multiwavelength sun photometers are described and briefly characterized. The SP-9 sun photometer is designed for year-round monitoring of the spectral air transparency in the 0.3–2.2 μm wavelength range in the regional network. To implement the automated measurement mode (unattended by operators), the instrument includes a solar sensor, an automatic sun pointing/tracking system, a built-in GPS detector, a flash drive, and sensors for meteorological parameters. The SPM portable photometer is a simplified version of SP-9 and is designed for the air transparency measurements in mobile conditions.
45 citations
TL;DR: In this article, a pulsed coherent Doppler lidar (PCDL) was used to estimate the dissipation rate of turbulent kinetic energy from wind measurements with conical scanning by a probing beam.
Abstract: The procedure of lidar data processing permitting one to estimate the dissipation rate of turbulent kinetic energy from wind measurements with a pulsed coherent Doppler lidar (PCDL) upon conical scanning by a probing beam is presented. The proposed algorithm for the PCDL data processing was tested and the error of the lidar estimate of the dissipation rate was calculated as a function of the number of full scans by a probing beam using numerical simulation.
36 citations
TL;DR: In this article, an algorithm for simulating laser beam propagation in a turbulent atmosphere under conditions of thermal blooming for the case where the beam is formed by a multielement aperture is presented.
Abstract: An algorithm for simulating laser beam propagation in a turbulent atmosphere under conditions of thermal blooming for the case where the beam is formed by a multielement aperture is presented. Coherent and incoherent combining of elementary fields of the multielement aperture is considered. Based on numerical simulation, properties of a combined beam are analyzed in comparison with an equivalent Gaussian beam. A complex diffraction pattern is shown to appear upon coherent combinig as a result of superposition of fields formed by individual elements of the initial aperture. Average values of maximum intensity, both of the Gaussian beam and the combined laser beam, little differ from each other when the nonlinearity parameter N c > 1. Under conditions of strong turbulence and strong nonlinearity, integral radiation characteristics of combined beams are close to characteristics of the Gaussian beam, the effective size of which is determined by sizes of the combined beam. The intensity of combined laser beams in a turbulent atmosphere fluctuates upon incoherent combining of fields to a lesser extent as compared to coherent combining.
29 citations
TL;DR: In this article, the results of the analysis of the backscattered radiation mean power enhancement in a turbulent atmosphere were presented, and it was shown that the laser return mean power in the turbulent atmosphere can two times exceed that in a homogeneous medium.
Abstract: The results of the analysis of the backscattered radiation mean power enhancement in a turbulent atmosphere are presented. The above enhancement arises because of the correlation of the forward and backward waves in a random media. The analysis was performed for the strong optical scintillation regime in a turbulent atmosphere. It is shown that the laser return mean power in the turbulent atmosphere can two times exceed that in a homogeneous medium because of the correlation of forward and backscattered waves. With an increase in the optical turbulence strength, the enhancement effect decreases according to the power law.
28 citations
TL;DR: In this article, the effect of decreasing light fluctuations in a coherent turbulence was investigated and first experimental data were considered, which confirmed the effect that decreasing light fluctuation can have on optical wave interactions with atmospheric coherent turbulence.
Abstract: Results on the problem of interactions between optical waves and atmospheric coherent turbulence are presented. First experimental data are considered, which confirm the effect of decreasing light fluctuations in a coherent turbulence.
27 citations
TL;DR: In this article, a numerical simulation-based algorithm is proposed for calculating the backscatter amplification (BSA) coefficient of laser radiation propagating in a turbulent atmosphere, which permits one to obtain results for conditions under which the known analytical calculation methods are inapplicable.
Abstract: A numerical simulation-based algorithm is proposed for calculating the backscatter amplification (BSA) coefficient of laser radiation propagating in a turbulent atmosphere. The algorithm permits one to obtain results for conditions under which the known analytical calculation methods are inapplicable. Using this algorithm, the BSA coefficient is analyzed numerically for different conditions of laser radiation propagation in the atmosphere.
25 citations
TL;DR: Based on MODIS satellite observations of aerosol optical depth (AOD) and active fires, as well as on data from the network for aerological radio sounding, this paper analyzed the spatiotemporal evolution of smoke aerosol on the territory of European Russia during the period of massive forest and peatbog fires in summer of 2010.
Abstract: Based on MODIS satellite observations of aerosol optical depth (AOD) and active fires, as well as on data from the network for aerological radio sounding, we analyzed the spatiotemporal evolution of smoke aerosol on the territory of European Russia (ER) during the period of massive forest and peatbog fires in summer of 2010. An interrelation is found between the structural features of the smoke-polluted regions and the processes of large-scale dynamics. The evolution of the smoke aerosol plume in the metropolitan area is described in detail. The statistical characteristics of AOD variations over ER during the fire period are calculated. The total column smoke aerosol is estimated. The radiation effects of smoke pollution of the atmosphere in the region are studied. The time evolution of the regional average shortwave radiative forcing of smoke aerosol at the top and bottom of the atmosphere is presented, together with the spatial distribution of local values of the radiative forcing in the period of maximum smoke pollution of ER. A statistically significant relation is found between MODIS-diagnosed number of active fires and wind speed and direction. The MODIS data on AOD are validated against observations at the AERONET station in Zvenigorod.
18 citations
TL;DR: In this article, the influence of the degree of transmitting beam coherence on the bit error rate in free-space optical communication systems is studied and it is shown that there are optimal values of the output power and degree of coherence of a transmitter optical beam, defined by the Fried radius, for all types of propagation paths (horizontal, vertical, or inclined) and different degrees of manifestation of turbulent effects.
Abstract: The influence of the degree of transmitting beam coherence on the bit error rate in free-space optical communication systems is studied. It is found that there are optimal values of the output power and degree of coherence of a transmitter optical beam, defined by the Fried radius, for all types of propagation paths (horizontal, vertical, or inclined) and different degrees of manifestation of turbulent effects. The optimal degree of coherence can be determined from the calculated BER minimum.
18 citations
TL;DR: In this article, a laboratory model of an optoelectronic communication system has been developed for experimental studies, where copper-vapor laser radiation at a wavelength of 510 nm was used as a source of signals.
Abstract: The paper considers the methods for theoretical and experimental study of bistatic optical communication schemes. A laboratory model of an optoelectronic communication system has been developed for experimental studies. Copper-vapor laser radiation at a wavelength of 510 nm was used as a source of signals. Test demonstration experiments were performed in the real atmosphere through atmospheric channels with a reflecting surface and a dense nonstationary aerosol-molecular structure. For theoretical studies, software means were developed for numerical statistical estimation of the energy and transfer characteristics of the bistatic atmospheric communication channels by the Monte Carlo method.
17 citations
TL;DR: In this article, a high-sensitive spectrometer operating in the range 20000-9000 cm−1 with an absorption sensitivity of 1 × 10−8 cm −1 and a spectral resolution of 0.05 cm− 1, based on the Bruker IFS-125M Fourier Spectrometer with a short multipass cell was described.
Abstract: A high-sensitive spectrometer operating in the range 20000–9000 cm−1 with an absorption sensitivity of 1 × 10−8 cm−1 and a spectral resolution of 0.05 cm−1, based on the Bruker IFS-125M Fourier spectrometer with a short multipass cell, is described. The high sensitivity of the spectrometer was gained through the use of the multipass absorption cell (a base length of 60 cm) with a high transmission (the ratio of the collecting mirror diameter to the base length is 1 : 4) and a high intensity light source.
17 citations
TL;DR: In this article, the authors studied the random walk of the center of mass of a vortex laser beam propagating in a medium with inhomogeneities in the dielectric permittivity.
Abstract: The work is devoted to studying the random walk of the center of mass of a vortex laser beam propagating in a medium with inhomogeneities in the dielectric permittivity. The beam is the circular mode of the Laguerre-Gauss beam LG0l. We have obtained estimates of the effect of turbulent propagation conditions, diffraction parameters, and azimuthal index (topological charge) of the beam on the magnitude of the variance of its center of mass displacements. We detected the “gyroscope effect” in which random displacements of the center of mass of the vortex of the laser beam turn out to be as small as the topological charge of the optical vortex included in the beam is large.
TL;DR: In this article, the light scattering matrix of a truncated plate-like droxtal oriented preferably in a horizontal plane has been calculated in the geometrical optics approximation and the main quantitative characteristics of the brightest halos have been obtained.
Abstract: Matrices of light scattering on a truncated plate-like droxtal oriented preferably in a horizontal plane have been calculated in the geometrical optics approximation. New halos are shown to appear due to the presence of truncated faces in the ice crystal. The main quantitative characteristics of brightest halos have been obtained. Based on the modified light scattering matrix, all 16 elements of the light scattering matrix are analyzed as compared to the case of light scattering by a hexagonal ice plate.
TL;DR: In this article, the formation and decay of diffuse channels of a corona discharge were studied in atmospheric pressure air, as well as optical and X radiation, and it was ascertained that wriggles appeared on the diffuse channels, the length of which increases towards the end of a voltage pulse.
Abstract: Formation and decay of diffuse “channels” of a corona discharge are studied in atmospheric pressure air, as well as optical and X radiation. Modulated (∼290 kHz) high voltage (∼250 kV) pulses of 10 ms were used. Soft X rays were recorded from a corona discharge in atmospheric pressure air. Bright glowing points were observed in the region of diffuse “channels” and plasma formations, at a distance from the channels. It was ascertained that wriggles appear on the diffuse “channels” of a corona discharge, the length of which increases towards the end of a voltage pulse.
TL;DR: In this article, conditions that make it possible to identify the type of the scattering medium by the form of the differential cross section in problems of remote sensing have been determined, and analytical expressions uniting specular scattering both on a set of particles and on a continuous surface have been obtained.
Abstract: Specular scattering is observed as a bright glint formed upon light reflection from cirrus clouds, snow cover, and a wavy water surface. Analytical expressions uniting specular scattering both on a set of particles and on a continuous surface have been obtained. Conditions that make it possible to identify the type of the scattering medium by the form of the differential cross section in problems of remote sensing have been determined.
TL;DR: In this paper, an eye-safe high spectral resolution lidar operating at a wavelength of 532 nm is proposed, where aerosol signals are filtered in an iodine-filled cell.
Abstract: A design is proposed of an eye-safe high spectral resolution lidar operating at a wavelength of 532 nm. Absolute calibration is ensured by a molecular channel where aerosol signals are filtered in an iodine-filled cell. Laser beam expansion in a transmitter via a receiving telescope ensures high thermo-mechanical stability of the design, which allows a small field-of-view and substantial reduction of the background noise level. A detailed optical circuit of the transceiver is shown, where the transmitter and the receiver are located on different sides of the optical bench for better stability. Specifications of the laser and the system are given. Lidar returns are calculated, and measurement errors are estimated. It is shown that the time of averaging should be no longer than 1 min to attain 10% accuracy when calculating the aerosol backscattering coefficient and optical depth in the troposphere. The system proposed is to operate continuously and unattended.
TL;DR: In this paper, a method of integral distributions is developed for determining the atmospheric aerosol microstructure from spectral measurements of the aerosol optical depth, and a software package developed based on it is presented.
Abstract: The method of integral distributions is developed for determining the atmospheric aerosol microstructure from spectral measurements of the aerosol optical depth. A numerical algorithm for solving the inverse problem and a software package developed based on it are presented. The specificity of the algorithm is in the allowance for the low level of information in the inverse problem with respect to particles from the microdisperse range of sizes. As a result of the software package operation, the integral size distribution function of the geometric cross-section of particles is retrieved. According to the function, the volume concentration and average radius of particles are calculated for the total ensemble and individual fractions of aerosol, submicron and coarse. A description of the user interface is presented. The software package is convenient in bulk processing the experimental data and does not require special knowledge for solving inverse problems from the user.
TL;DR: In this article, an inverse problem of atmospheric transport is solved as applied to the estimation of monthly average surface CO2 fluxes for 2009 using ground-based observation data and GOSAT data beginning from June, 2009.
Abstract: An inverse problem of atmospheric transport has been solved as applied to the estimation of monthly average surface CO2 fluxes for 2009 using ground-based observation data and GOSAT data beginning from June, 2009. Corrections to the flux fields for each kind of sources are represented as a linear combination of main flux components of the corresponding surface gas-exchange fields. To calculate the atmospheric transport, the coupled Eulerian-Lagrangian model (GELCA) is used. A large array of observation data is used (3000–5000 observations per month); therefore, the Fix-Lag Kalman Smoother is used, which allows monthly fluxes to be estimated sequentially, according to a chosen size of assimilation window. The calculation results are represented in the form of 2D fields of monthly average flux fields, and recalculated for chosen regions. The calculations show a significant decrease in the posterior flux uncertainty when using GOSAT observations.
TL;DR: In this article, the dependence of energy characteristics of an average volume CuBr laser with and without addition of HBr on the rate of discharge current rise is studied, and the energy characteristic is varied by connecting an additional inductance in the discharge circuit.
Abstract: The dependence of energy characteristics of an average-volume CuBr laser with and without addition of HBr on the rate of discharge current rise is studied. The energy characteristic is varied by connecting an additional inductance in the discharge circuit. It is shown that the average lasing power of the CuBr laser decreases tenfold with an increase in the inductance up to 4 μH. Under similar conditions, the average lasing power of the CuBr laser with addition of HBr decreases by less than two times. The fraction of lasing at the yellow line changes less. Thus, the presence of an electronegative addition to the active medium of a CuBr laser decreases requirements for the pulse power supply.
TL;DR: In this article, two possible mechanisms of stratospheric control of the ozone concentration and dynamics in the troposphere were considered, i.e., total ozone-caused modulation of the ultraviolet radiative flux, incoming to the Troposphere and initiating therein the photochemical processes.
Abstract: We consider two possible mechanisms of stratospheric control of the ozone concentration and dynamics in the troposphere. The first mechanism is implemented through the total-ozone-caused modulation of the ultraviolet radiative flux, incoming to the troposphere and initiating therein the photochemical processes. The second mechanism acts through direct transport of stratospheric ozone, which will “trigger” the photolysis and initiate these same processes of ozone generation, but now in the troposphere. Both of these mechanisms of stratospheric ozone control of the near-ground ozone concentration are shown to be apparent near Tomsk. It is noteworthy that the control via ultraviolet flux determines the amplitude modulation, and the transport from the stratosphere to the troposphere drives the temporal modulation.
TL;DR: In this paper, the authors proposed an algorithm which combines the iteration retrieval of the optical single-scattering characteristics directly from the data of photometric measurements and the solution of the linear inverse problem which ensures the retrieval of microstructure of homogeneous aerosol particles and complex refractive index of the aerosol material.
Abstract: The ground-based measurements of direct and scattered solar radiation to date serve as the most reliable source of information on the columnar optical and microphysical characteristics of atmospheric aerosols. We suggest an algorithm which combines the iteration retrieval of the optical single-scattering characteristics directly from the data of photometric measurements and the solution of the linear inverse problem which ensures the retrieval of the microstructure of homogeneous aerosol particles and complex refractive index of the aerosol material. Software, developed to make the routine experimental data processing more efficient, is described. Results of algorithm testing on different mono- and multi-component aerosol models are presented.
TL;DR: In this paper, the experimental results of remote detection of vapors of some atmospheric chemical compounds using a Raman lidar system with a narrow-line excimer KrF laser and a multichannel spectral analyzer, based on a diffraction spectrograph and an intensified CCD camera, are presented.
Abstract: The experimental results of remote detection of vapors of some atmospheric chemical compounds using a Raman lidar system with a narrow-line excimer KrF laser and a multichannel spectral analyzer, based on a diffraction spectrograph and an intensified CCD camera, are presented. The system sensitivity is estimated for a sounding range of 6–10 m. Using additional means for suppressing the intense Raman bands of N2 and O2 molecules, a detection threshold of 1 ppm is reached. Base rovibrational Raman bands of oxygen and nitrogen and their first overtones are observed during experiments on noise level estimation and Raman spectra recording in the atmosphere. The absence of overlapping of fluorescence and Raman signals is confirmed experimentally.
TL;DR: In this paper, the average values of the aerosol optical and microphysical characteristics retrieved according to data from photometric measurements at the AERONET station in Tomsk during 2004-2009 for situations when the optical depth in the spectral channel of 440 nm did not exceed 0.4.
Abstract: We present the results of the study of sensitivity of our algorithm for retrieving the columnar aerosol optical and microphysical characteristics to measurement errors. The algorithm testing against data from field measurements under conditions of both increased and moderate aerosol turbidity of the clear sky atmosphere is discussed. We present the average values of the aerosol optical and microphysical characteristics retrieved according to data from photometric measurements at the AERONET station in Tomsk during 2004–2009 for situations when the aerosol optical depth in the spectral channel of 440 nm did not exceed 0.4.
TL;DR: In this paper, the authors presented an approach to extract the regular component of diurnal behavior of the aerosol optical depth and columnar water vapor of the atmosphere, compared with that in the suburban background region, as well as in a few other regions: Tomsk, Yekaterinburg, Irkutsk, Yakutsk and Ussuriisk.
Abstract: We present an approach to extracting the regular component of diurnal behavior of the aerosol optical depth and columnar water vapor of the atmosphere. The daily average dynamics of these characteristics in Tomsk is compared with that in the suburban background region, as well as in a few other regions: Tomsk, Yekaterinburg, Irkutsk, Yakutsk, and Ussuriisk. We identified common features in the dynamics for the regions of Tomsk, Yekaterinburg, and Irkutsk. Some specific features, caused by the effect of local factors, are revealed for Yakutsk and Ussuriisk. We present parameters of approximation of the daily average behavior of the atmospheric AOD for Yekaterinburg, Tomsk, and Irkutsk.
TL;DR: In this article, the threshold relation between the strength of laser beam focusing and its peak power was determined for post-focal filamentation on the basis of the experimental data and numerical simulations.
Abstract: The threshold relation between the strength of laser beam focusing and its peak power is determined for post-focal filamentation on the basis of the experimental data and numerical simulations. The dynamics of the post-focal filamentation can vary (propagating or reconstruction type) depending on the strength of linear beam focusing.
TL;DR: In this article, the results were obtained using two algorithms for solving the inverse problem, a basic one and its modification presented in the first part of the paper, in order to increase the accuracy of the estimate for the contribution of microdispersed particles to the aerosol microstructure.
Abstract: Atmospheric aerosol microstructural parameters retrieved from spectral measurements of aerosol optical depth in the summer period in Tomsk are considered. The results were obtained using two algorithms for solving the inverse problem, a basic one and its modification presented in the first part of the paper. In the basic algorithm, the method of integral distributions is implemented. Having advantages of the method of integral distributions, the modified algorithm makes it possible to increase the accuracy of the estimate for the contribution of microdispersed particles to the aerosol microstructure. Statistical data about the retrieved parameters obtained for a total ensemble of particles with separation into the submicron and coarse fractions are presented. It is found that applying the modified algorithm permits one to additionally take into account up to 47% of the volume of submicron particles on average. At the same time, correction of the solution in the microdisperse range of particle size leads to a decrease in their average radius from 0.16 to 0.1 μm.
TL;DR: In this article, possibilities of measurements of the turbulent energy dissipation rate with a pulsed coherent Doppler lidar (PCDL) are studied in the case of conical scanning with a probing beam, with allowance for the averaging of the radial velocity over the sensing volume and error of estimates of radial velocity.
Abstract: Using numerical simulation, possibilities of measurements of the turbulent energy dissipation rate with a pulsed coherent Doppler lidar (PCDL) are studied in the case of conical scanning with a probing beam, with allowance for the averaging of the radial velocity over the sensing volume and error of estimates of the radial velocity. The error of the lidar estimate of the dissipation rate was calculated as a function of the number of full scans with a probing beam and of the signal-to-noise ratio. A comparative analysis was performed for the results of joint measurements of the dissipation rate by sonic anemometers and 2-μm PCDL.
TL;DR: In this article, a review of literature data and results of a series of experiments made by the authors shows that the problem of UV absorption by atmospheric water vapor has not yet been solved satisfactorily.
Abstract: The review of literature data and results of a series of experiments, made by the authors, shows that the problem of UV absorption by atmospheric water vapor has not yet been solved satisfactorily. The attempts to propose a reliable model of atmospheric H2O contributions to the attenuation of UV radiation propagating through the atmosphere or for analysis of data obtained with instruments for atmospheric composition monitoring have not been successful. Additional measurements of the spectral dependence of the absorption cross-section within the 200–400 nm range are required.
TL;DR: In this paper, 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.
Abstract: 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.
TL;DR: In this article, the question of stratosphere-troposphere exchange in the transitional “oceancontinent” zone by means of lidar measurements of the vertical ozone distribution in 2007-2009 was investigated.
Abstract: This paper covers the question of stratosphere-troposphere exchange in the transitional “oceancontinent” zone by means of lidar measurements of the vertical ozone distribution in 2007–2009. The simultaneous analysis of the vertical ozone distribution, weather and wind field parameters shows that the stratosphere-troposphere exchange over Vladivostok is caused generally by tropopause folds, which are formed due to stratospheric air motion from north to south and then into the troposphere to the southwest of the major cyclones. In this case, a positive trend of ozone concentration and a decrease in air humidity in the upper troposphere occur when polar air masses form the polar jet stream in the vicinity of the subtropical jet stream. Hence, the location of kernels of both jets becomes unstable and a tropopause inversion layer breaks down, which leads to a possibility of stratospheric air intrusion into the troposphere in the region of mutual influence of the jets.
TL;DR: In this article, the analysis of seasonal features of the carbon dioxide exchange process in the littoral of the Southern Baikal during the open-water period is devoted to results obtained during the fall period.
Abstract: This paper is the next in a series of publications dealing with the analysis of seasonal features of the carbon dioxide exchange process in the littoral of the Southern Baikal during the open-water period, and devoted to results obtained during the fall period. It is shown that variations in the concentrations of dissolved gases and biogenic elements in the surface waters of the Lake Baikal littoral during fall are opposite in character to the process observed during the spring-summer period. The concentrations of carbon dioxide, oxygen, nitrates, and phosphates increase from the second half of September toward December. The sink of CO2 from the atmosphere into the water surface is still observed during early October in the Baikal littoral, with its diurnal budget being comparable in value to the daily average sink during the period of hydrological summer. The daily average CO2 flux reverses sign in November, and the lake surface becomes a source supplying carbon dioxide to the near-water atmosphere; the CO2 supply rate keeps increasing and reaches a maximum level during December, i.e., until the beginning of freezing-over period. At the beginning of this period, an additional small CO2 amount can be expected to be supplied to the atmosphere of the littoral zone due to the process of premorning freezing and a subsequent ice melt.