Home – Home – Jornals – Atmospheric and Oceanic Optics 2020 number 7

The absorption spectra of carbon dioxide confined in aerogel sample with pore sizes of 60 nm have been recorded at a room temperature in the 2250-2400 cm^-1 region using a Bruker IFS 125HR FTIR spectrometer. Parameters of spectral lines of CO₂ are derived; their dependence on rotational quantum numbers are shown. The results are compared with data available in literature.

Lidar observations at Siberian Lidar Station (SLS) of Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences in Tomsk (56.5°N; 85.0°E) showed the presence of stratospheric aerosol layers over Tomsk during winter 2017-2018, signs of descending air masses, and deficit of ozone. Aura OMI/MLS observations indicated that in December-January 2017/2018 the total ozone (TO) content and NO₂ content in the stratosphere over the Northern Eurasia, as well as the temperature in the stratosphere, were significantly lower than normal. Analysis of back trajectories and integrated (over profile) TO showed that the dynamic disturbance of the Arctic stratosphere in December 2017 led to extrusion of cold air masses with excessive reactive chlorine (in view of NO₂ deficit) beyond the Arctic circle and their intrusion into the stratosphere of Tomsk. Seemingly, in the Tomsk stratosphere they were exposed to solar radiation and, staying chemically isolated, evolved into chemically disturbed state, similar to the state of springtime Arctic stratosphere, where ozone is intensely destroyed until the final warming.

The special features of hydrooptical signals of an airborne polarization lidar are theoretically and experimentally analyzed in the case of sensing of homogeneous water mass under controllable conditions. The results obtained expand the possibilities of interpretation of lidar return signals, especially in complex and ambiguous situations. Results of theoretical and experimental investigations of the depth profiles of hydrooptical signals of airborne polarization lidars operated under conditions of homogeneous water depth are presented.

The solution to the problem of light scattering by spherical particles is presented, adapted for the interpretation of lidar signals for applied problems. The solution was obtained for typical wavelengths used in laser sensing 0.355, 0.532, 0.905, 0.940, 1.064, 1.55, 2.15, and 10.6 mm within the Mie scattering theory for water and ice. The inherent high-frequency oscillations in the backscattering direction are smoothed out by means of a moving average, which allows one to construct fast and efficient algorithms for particle size distributions observed in the atmosphere.

The interrelationships between the variations in CH₄, CO, CO₂, NO, NO₂, O₃, and SO₂ concentrations and the aerosol number density and such meteorological quantities as air temperature, atmospheric pressure, wind direction and speed, global solar radiation and ultraviolet radiation in the range 295-320 nm, relative humidity, and partial pressure of water vapor are studied. For that, we used data on monitoring the air composition (for the period 1993-2018) performed at the TOR-station of IAO SB RAS located in Tomsk.

CO₂ spatial and temporal variability in five Russian regions has been analyzed on the basis of OCO-2 satellite measurements (more than 300 days during 4.5 years, more than 50 000 measurements). The Orbiting Carbon Observatory-2 (OCO-2) allows measurements of CO₂ content with a high accuracy (0.25-0.5%) (for data with a quality flag “0”), a high horizontal resolution (1.29^{´ 2.25 км2), and a spatial coverage along paths of ~ 10 km. That makes it possible to analyze the spatial and temporal variations in CO₂ column-averaged dry-air mole fractions (XCO₂). XCO₂ OCO-2 data with quality flag “1” has lower measurement accuracy, but the number of such measurements is 5-10 times greater than that with quality flag “0”. XCO₂ satellite measurements with quality flag “0” in the vicinity of Moscow, Saint Petersburg, Yekaterinburg, Magnitogorsk, and Norilsk (circles with a radius of 100 km from the city centers) have been analyzed. Comparisons of the meaurements in different cities and regions show that XCO₂ datasets with a quality flag “0” are homogeneous, the amplitude of XCO₂ variations amounts to 5-6%, root mean square variations are less than 1%. The maximum values of XCO₂ spatial variations totals 2-4%, which differs significantly from the results of the analysis of OCO-2 XCO₂ data with quality flag “1”.}

The results of a large-scale investigation of carbon dioxide and methane distribution carried out in Western Siberia in 2018-2019 using a Picarro G4301 portable gas concentration analyzer are presented. The analysis of the obtained data enabled the spatial distribution of background concentrations of CO₂ and CH₄ to be retrieved with a high resolution. The revealed inhomogeneities in the CO₂ and CH₄ distribution is a result of both the effect of ecosystem features in different regions of West Siberia and the characteristics of their seasonal cycles.

The passive technique for crosswind velocity retrieval from a video series of incoherent images, developed in previous works, has been tested. The technique is based on the visualization of air-drifted turbulent air inhomogeneities which distort optical images recorded. The results of retrieval of the crosswind velocity by the technique suggested are compared with anemometer measurements at paths of up to 1 km in length.

The alignment technique and quality check of the large mirror of the Siberian lidar station (SLS) with the diameter of 2.2 m is considered. The results of computer simulation of the field aberrations of the large mirror are presented and the area of the coma-free region is determined. The spot diagram of the large SLS mirror is measured by estimating the image size of stars passing through the zenith are presented. The numerical simulation of the lidar signal using ray tracing in the optical CAD ZEMAX is carried out taking into account the influence of a real scattering circle of the receiving optical system. The shape of the experimentally registered and ray tracing simulated lidar signal is compared.

To validate the atmospheric general circulation models ECHAM5-wiso and ECHAM6-wiso with embedded water isotopic modules, the simulation with nudging to known fields of temperature, pressure, wind speed and direction obtained from retrospective climate analysis was performed. The simulation results were compared with data on the isotopic composition (dHDO and dH₂¹⁸O) of water vapor in atmospheric air near the surface obtained at two monitoring stations: in Labytnangi (66.660N, 66.409E) and in Igarka (67.453N, 86.535E). An unambiguous conclusion about the superiority of the newer model ECHAM6-wiso could not be made, because the simulation results with its use demonstrate a better agreement with the values observed in Igarka, while the model ECHAM5-wiso shows a better agreement with the values observed in Labytnangi. The simulation results can be used as an a priori ensemble for solving inverse problems of remote sensing of the atmosphere in Western Siberia.

The contradiction between the results of determining the phase velocities of sea waves from optical images of the sea surface and data of in situ measurements by an array of wave sensors is analyzed. The phase velocity estimates obtained from optical images well correspond to the theoretical values derived from the linear dispersion relation for gravitational waves. For in situ waveform measurements, the phase velocities exceed the theoretical values. It is shown that the excess is caused by the fact that when in situ measurements are made, the contribution to the phase spectrum is given by waves that come from different directions and have different projections of the phase velocity in the direction in which it is determined.

An increase of 50% in the amplitude of the photoacoustic signal generated when water vapor absorbs pulses of laser radiation at 266 nm with circular polarization, relative to the signal for radiation with linear polarization, is reported. The effect observed is associated with different dissociation efficiency of H₂O molecules as a result of one- and two-photon absorption of radiation with linear and circular polarization.