Home – Home – Jornals – Atmospheric and Oceanic Optics 2022 number 12

The results of high-sensitivity recording of the Wulf group absorption bands of the ozone molecule in the range 9350-10000 cm^-1, which corresponds to transitions from the ground to an excited triplet electronic state, are discussed. The spectrum in this range above the main molecular dissociation threshold was recorded for the first time with the use of a cw-CRDS spectrometer with sensitivity of 1 × 10^-10 cm^-1 in terms of the absorption coefficient. The measurement technique and the procedure of ozone generation and its concentration monitoring are described. A comparison with the previously calculated theoretical spectra of the ³A₂(000) ← X¹A₁(000), ³A₂(010) ← X¹A₁(000) and ³A₂(010) ← X¹A₁(010) singlet-triplet bands is carried out.

Based on known expressions applied to diffraction-limited optical systems, estimates are given and a method is proposed for determining the measurement error of the longitudinal coordinates of particles from images reconstructed from digital holograms. A correction factor for visual focusing is determined for different distances between a detected particle and the plane of a CMOS matrix. The experimental results of testing the method are presented. It is shown that the error of automatic digital focusing can be reduced by simultaneously applying focusing curves for several quality indicators and optimizing the image area for their construction.

The long-term measurements of the aureole scattering phase function are analyzed for angles φ = 1.2° and 20° ( I_1.2 and I₂₀), which were obtained using a closed-type halo photometer at the aerosol station of the LAO of the IAO SB RAS in 2010-2021. The analysis of the temporal variability of the parameters was carried out for interannual and annual data and the diurnal behavior of hourly measurements. The daily averages were calculated from the hourly averages, the monthly averages, from daily averages and the annual averages, from the monthly averages. A weak but significant ( p = 0.05 level) time trend was found only for the interannual values of I_1.2, which amounted to 1.14% per year. In the annual course of I_1.2, a monotonous increase in the values from winter to summer months is clearly observed. In the annual course of I₂₀, we see a decrease in values from winter to summer. Smokes from distant wildfires in 2012 and 2016 and partially in 2018 and 2019 disrupt this pattern with increased I₂₀ values in July and insignificantly in June, August, and September. The diurnal behavior of the aureole scattering phase function values I_1.2 and I₂₀ and the ratios I₂₀ / I_1.2 constructed for the annual variation of monthly average daily values are typical of the behavior of surface aerosol under continental conditions. Smokes from remote wildfires lead to high values of I₂₀ at night, morning, and evening, and the decrease in I₂₀ during the daytime is insignificant with a probability of 0.95 due to the high standard deviation.

The paper considers the propagation of high-power femtosecond laser radiation through aerosol. The propagation of high-power femtosecond laser radiation is simulated with flat phase screens that simulate the passage of radiation through an aerosol layer, which has effective optical parameters corresponding to different intensities during nonlinear interaction. In the course of experimental studies, the effect of aerosol on the position and length of the filamentation domain and the number of filaments was shown. With a decrease in the concentration of aerosol particles in the air in front of the filamentation domain, the filamentation domain approaches and its length increases to the same size as without aerosol, and the number of filaments also increases.

In with paper we demonstrate the application of original method for solving the inverse problem of hyperspectral satellite sensing to retrieval of the vertical profile of HDO/H₂O ratio in the Earth's atmosphere with the simultaneous use of thermal and near-IR spectra is described. This method is used to retrieve relative abundance of HDO isotopologue (δD) in atmospheric water vapor from measurements of TANSO-FTS IR spectrometer onboard GOSAT-2 satellite for the first time. Retrieved δD-values are compared with data obtained at ground-based TCCON measurement station in Karlsruhe, Germany. The simultaneous use of satellite spectra of outgoing atmospheric radiation in the thermal range and reflected solar radiation in the near-IR shows a higher correlation between monthly average δD satellite values of and ground-based data.

The ranges of changes in the parameters of wind and temperature (refractive) turbulence estimated from lidar data, corresponding to the intensity of aircraft shaking severity caused by turbulence in the free atmosphere at flight altitudes, are determined. It is shown that both the estimation of the variance of the radial velocity measured by a coherent lidar in the direction of flight, and the determination of the structural constant of the refractive index from the data of the lidar, which measures the intensity of refractive turbulence in flight direction, make it possible to judge the potential danger of aircraft shaking severity in clear air turbulence zones ahead of the aircraft.

The paper presents the results of analysis of radar characteristics of clouds, including the polarization ones, and lightning data for June 9 2020, in the vicinity of Saint-Petersburg. The characteristics of thunderstorm and clouds without lightning are compared. Statistical difference between two groups of clouds has been found. The regression analysis of the correlation between the lightning flash rate and radar characteristics of clouds is performed using neural networks. The impact of these parameters on lightning flash rate has been estimated. A mathematical equation for calculating the lightning flash rate using the differential reflectivity maximum and the cloud volume with the reflectivity equal to 35 dBZ is derived.

The paper analyzes the time and space derivatives of the wind vector components and the derivatives in the case of resolution into deterministic, meso-gamma-scale, and turbulent parts. Experimental data on the wind vector components obtained in the surface air layer with ultrasonic thermoanemometers were used for the analysis. The main task was to estimate the values and the variability ranges of the derivatives including meso-gamma-scale variations in the wind field. The aim of the study was to compare the variability ranges of these derivatives with those of the “classical” derivatives (when only deterministic and turbulent parts of the wind vector are considered). It is shown that meso-gamma-scale variations in the wind vector components can be no less important than the turbulent parts included in the “classical” schemes used for simulation (prediction) of the wind field with high space and time resolution.

The work is devoted to the study of the dynamics of greenhouse gas flows, which were measured from 2017 to 2021 at the Background Observatory of Institute of Atmospheric Optics SB RAS. It is shown that the annual average SO₂ flows at the observatory varied from -283 mg × m^-2 × h^-1 (runoff) to +31 mg × m^-2 × h^-1 (emission). The minimum emission of 1351 mg × m^-2 × h^-1 was recorded in 2019 and the maximum emission of 1789 mg × m^-2 × h^-1 in 2021. The lowest runoff was observed in 2017 (2099 mg × m^-2 × h^-1). The largest, equal to 2304 mg × m^-2 × h^-1, was in 2018. The annual average methane fluxes ranged from -0.032 mg × m^-2 × h^-1 in 2018 to -0.047 mg × m^-2 × h^-1 in 2020. The maximum methane emission was recorded in 2018 and was equal to 0.915 mg × m^-2 × h^-1, and the minimum in 2021 was only 0.095 mg × m^-2 × h^-1. At the same time, the maximum runoff in the interannual variability varied in a narrower range from -0.241 to -0.361 mg × m^-2 × h^-1. Unlike SO₂ and SN₄, the soil of the measurement area turned out to be a weak source of N₂O. The annual average fluxes of this gas were in the range 0.00-0.011 mg × m^-2 × h^-1. Internal maximum emissions from 0.237 to 0.301 mg × m^-2 × h^-1 and runoffs from -0.206 to -0.245 mg × m^-2 × h^-1 also changed little.

The impact of the water vapor continuum absorption in the atmosphere on CO₂ radiative forcing is estimated on the basis of mass calculations of thermal radiative fluxes for summer conditions in 2021 in the Lower Volga Region. The set of 368 vertical atmospheric profiles (four realizations per day during three summer months) was used for the simulation. It was shown that the humidity growth decreases the CO₂ contribution to radiative impact on the Earth’s surface, which leads to weaker heating of the surface and stronger heating of the atmosphere. Thus, greenhouse effect reinforcement due to the CO₂ concentration increase at high humidity will lead to greater heating of the atmosphere. The water vapor continuum plays a dominating role in this process, but not selective absorption in H₂O bands.

The spatial and temporal variability of forest floor moisture characteristics is analyzed on the basis of the Canadian Fire Forest Weather Indices (CFFWIS) for the territory of Western Siberia (45-75° N, 60-90° E) over 2016-2021 for the first time. The floor moisture effect on the number of wildfires (hotspots) during the warm season (March-October) is assessed. The results are given for different natural zones. Statistically significant correlations are found between hotspots and floor moisture at a depth of 7 cm only in some spring and summer months (correlation coefficient is up to 0.54). The strongest effect (correlation coefficient is up to 0.60) on wildfires is observed for floor moisture at a depth of 1.2 cm in the south of Western Siberia in April. Thus, it can be concluded that the forest floor moisture is an important parameter in description of conditions for fire initiation and development. However, the question about its effect on the wildfire behavior remains open and requires additional research accounting meteorological and atmospheric conditions. The results can be used in future for solving problems of forecasting the potential fire danger.

The impact of aerosol sources on the atmosphere pollution of Russian Arctic sector is underestimated. The newly aerosol station was installed on Bely island (Kara sea) in August 2019, it is located on the way of air mass transportation from industrial regions of Western Siberia to the Arctic. Continuous aethalometric measurements of short leaving climate tracer - black carbon are carried out. They showed the seasonal variability with high values from December to April (60 ± 92 ng/m³) and low in June-September (18 ± 72 ng/m³). Pollution events with concentration higher background are identified. Regional distribution of fossil fuel and biomass burning sources are obtained by the concentration weight trajectory model. Impact of gas flaring from oil and gas extraction areas of Western Siberia, Volga-Ural, and Komi Republic is the most pronounced during the cold period while the wildfire smoke emissions are dominated in warm season. The difference between the black carbon concentrations in ultraviolet and infrared wavelength regions serves as a marker of biomass burning impact on the aerosol composition, indicating the residential wood combustion and agriculture and wildfires during cold and warm season, correspondently.

A technique has been developed and a calculation has been made of the irradiance of the entrance pupil of a ground-based optoelectronic system (OES) from a cylindrical space object illuminated by the Sun at night. The results of calculating the minimum irradiance and corresponding stellar magnitude at the input pupil of the OES are presented with a signal-to-noise ratio at the output of the photodetector matrix with a current equal to 7 in the wavelength range of 0.45 ÷ 0.85 mm. The dependence of the signal-to-noise ratio on the distance to the space object for its three different sizes is constructed. The program ROSN-1 was developed and its control panel was presented for calculating the characteristics of ÷ 0.85 mm was presented, and the possibilities of this program were explained.

The features of high-power and high-contrast imaging in a bistatic laser active optics system (laser monitor) are considered. In the developed system, a brightness amplifier has a larger volume than an illumination source, which makes provides for high-power contrast images of micro objects. For the first time, the influence of the time shift between a superradiance pulse of the amplifier and the time of signal arrival at its input on the contrast and power of images formed by one pulse was was ascertained. It is shown that artifacts formed as a result of the superluminous radiation "parasitic" reflection and scattering from optical circuit elements significantly reduce the contrast and power of the generated signals. This effect can be eliminated by the generation of an amplifier input signal before the generation of amplified spontaneous emission. The optimal delay is 1 ns.