Home – Home – Jornals – Advanced Search

Water vapor is a significant component of the Earth's atmosphere. Assessing the contribution of water vapor to the Earth's radiation balance has remained a topical issue for decades. In this work, the water vapor self- and foreign-continuum spectra have been retrieved at temperatures of 310, 325, and 340 K in the 1600 cm^-1 absorption band for the first time based on earlier Fourier-measurements of water vapor absorption under self-broadening and broadening by air at 296-340 K within this absorption band with the use of HITRAN2020 spectroscopic database. The retrieved spectra show characteristic for self- and foreign-continuum spectral and temperature dependences. The spectra we retrieved are compared with the MT_CKD semi-empirical continuum model and the semi-empirical dimer-based continuum model ( Simonova A.A., Ptashnik I.V., Shine K.P. Semi-empirical water dimer model of the water vapour self-continuum within the IR absorption bands // J. Quant. Spectrosc. Radiat. Transfer. 2024. V. 329. P. 109198-1-19. DOI: 10.1016/j.jqsrt.2024.109198). The results are important from both fundamental, within the molecular spectroscopy, and practical point of view, in problems of atmospheric modeling and remote sensing.

Bio-optical parameters of seas of the Far East region obtained from the MODIS/AQUA radiometer data are analyzed. The results of two main atmospheric correction algorithms based on the following assumptions are compared: the absence of water-leaving radiance in the near-infrared spectral bands and the stability of the sea water spectral shape in this range (MUMM). Verification was carried out using data of Japanese and Korean AERONET-OC stations. An approach to improving the results of MUMM atmospheric correction by using a regional adjustment of the color indices is considered. The MUMM correction after adjustment is not inferior to NIR correction in terms of the calculation accuracy of chlorophyll- a concentration. It was found that the recommended NIR correction leads to negative reflectivity coefficients Rrs at a wavelength of 412 nm in 10% of cases. These cases correspond to highly trophic waters and are accompanied by an overestimation of the chlorophyll-a concentration by an average of 1.8 times. The proposed correction of the color indices does not lead to negative values of Rrs; the color indices in the blue spectral range have significantly lower errors than those of the NIR algorithm. The proposed approach ensures more reliable estimates of bio-optical parameters of the sea based on satellite data.

The work is devoted to the study of the effect of aerosols on various processes in the atmosphere, in particular, the formation of convective clouds and their electrification. The special cases of thunderstorms in the Krasnoyarsk Territory during wildfires are considered. This region is characterized by the highest risk of increased wildfires due to the climate change among Russian regions. The thunderstorm events were selected based on the analysis of lightning activity in the selected area from 2015 to 2022 in comparison with wildfire data. A series of numerical experiments on simulating thunderstorms in the WRF model with different aerosol concentrations in the atmosphere have been performed. Based on the simulation results, electrical parameters of clouds have been calculated. To find correlations between the density of lightning discharges and the parameters of convective systems we suggest methods for estimating lightning activity based on the volume of thunderstorm cells with a certain radar reflectivity and the area of high electrical potential. We have revealed that an increase in the aerosol load in the atmosphere increases the time of convection development, as well as a significant effect of aerosol concentration on electric potential maximum at near constant radar reflectivity maximum. The results can be used to develop fundamental ideas about the relationship between lightning activity and wildfires and to improve methods for predicting lightning activity.

The problem of atmospheric emission source identification using remote sensing data is considered. An algorithm is proposed for a three-dimensional model of atmospheric pollutant transport and a nonlinear measurement model represented as a “differentiable black box". The algorithm is based on sensitivity operators and ensembles of adjoint equations solutions. It was tested on a realistic scenario for identifying soot sources for the Baikal region with synthetic satellite measurements of the Terra/MODIS platform, which showed its applicability. Additionally, the measurement data decomposition modification of the algorithm is proposed, which made it possible to reduce the relative error of retrieving the source function by 12% compared to the version without decomposition. The results can be used in the development of remote sensing data processing systems.

In atmospheric remote sensing, particularly in the interpretation of lidar signals from cirrus clouds, the accuracy of light scattering modeling on non-spherical randomly oriented ice particles plays a crucial role. Although the physical optics approximation is commonly used due to its computational efficiency, it does not always provide sufficient accuracy, especially when particle sizes are comparable to the wavelength of incident radiation. This introduces systematic errors into scattering matrix databases used for solving inverse problems. This study employs the discrete dipole approximation to verify the validity of the physical optics approximation. The primary focus is on comparing results obtained at wavelengths of 0.532 and 1.064 mm for particles of various shapes and sizes from 2 to 8 wavelengths. It is shown that in this size range, the physical optics approximation leads to relative errors of up to 20% in the linear depolarization ratio and reduces the backscattering intensity by half. The findings enable a more precise estimation of the applicability limits of the physical optics approximation and provide corrections for existing scattering matrix databases. This, in turn, will improve the accuracy of lidar data interpretation and enhance the quality of microphysical retrievals for cirrus clouds.

Highly directional supercontinuum (HDSC) is a unique source of broadband coherent radiation. To create such a source, it is necessary to know the parameters and conditions of its occurrence. The article presents the results of experimental study of the conditions for HDSC generation in gaseous nitrogen pumped by a radiation pulse with wavelength of 950 nm, duration of 70 fs, and energy of 3-6 mJ. The pump radiation was focused into a gas chamber by a spherical mirror with F = 75 cm under aberration conditions (the angle of incidence of the radiation on the mirror was 15°). It is shown that there is optimal pump energy of 4.5 mJ and gas pressure of 3-4 atm. The spectral composition of the HDSC covers the range from 350 to 1000 nm. The divergence of HDSC radiation is diffraction-limited and its greatest value (the diameter of the white spot in the far zone) corresponds to a wavelength of 780 nm. The maximal HDSC energy was 17 μJ. The results are useful for understanding the physical mechanisms underlying the emergence of HDSC, as well as for developing broadband coherent radiation sources.

A study of hydrogen oxidation in the presence of sulfur dioxide was conducted in an oscillatory mode. It was found that this process occurs via a degenerate chain mechanism, with sulfur oxide (SO), the primary product of sulfur dioxide conversion, playing a significant role. It was shown that the hydrogen oxidation reaction in the presence of sulfur dioxide in the autoignition region under certain conditions (pressure, temperature, gas mixture composition, contact time) proceeds explosively and is accompanied by light emission. A comparison of experimental data on hydrogen oxidation in the presence of sulfur dioxide with the results of calculations using the proposed model of the process under study revealed good agreement. Based on the calculation results, the effective activation energy of the reaction was determined to be 9 200 J/mol.

The paper presents the results of experimental determination of the flammability concentration limits of methane--air--water vapor, methane--hydrogen--air--water vapor mixtures with a methane to hydrogen volume ratio of 1:2 and 2:1, and carbon monoxide--hydrogen--air--water vapor mixtures with a hydrogen to carbon monoxide volume ratio of 4:1 at an initial temperature of 150 °C and a pressure of 101 kPa. The water vapor content varied in the range of 0 ÷ 60 vol. %. The experiments were conducted in a spherical chamber with a volume of 100 dm3. The presence of mixture ignition and flame propagation were recorded using infrared imaging. The flammability limits of the methane--air--water vapor mixture obtained in the experiments are in agreement with the data available in the literature. The flame propagation mode in hydrogen-containing mixtures near the lower concentration limit was recorded in the form of a spherical flame turning into a toroidal vortex.

The effect of chemical nonequilibrium in the combustion process of a diffusion methane-air flame at moderate pressures and temperatures of the initial reactants on the reduction of nitrogen oxide in reactions known as NO reburn was studied. Based on the detailed mechanism of chemical kinetics of methane oxidation GRI-Mech 3.0, an analysis was performed of the distribution of the main NO-reducing substances (CH, CH₂, CH₃, HCCO) in reburn reactions, as well as the initial substances forming NO in Zeldovich reactions, across the thickness of a diffusion laminar flame based on a numerical solution of the Peters-Kuznetsov system of equations using the thin flame front model (flamlet model). In the flame representation as a chain of isolated ideally mixed reactors distributed across the flame thickness, the NO concentration was estimated using a precise analytical formula representing the rates of reburn reactions in accordance with three detailed kinetic mechanisms: GRI-Mech 3.0, Glarborg, and Miller---Bowman. A comparative assessment of the efficiency of these mechanisms for reducing NO concentration was performed; the maximum reduction was 13.3, 23, and 30.4%, respectively. An assessment of the influence of diffusion showed a change in the relative concentration of NO profiles by no more than 0.06%. It was also shown that, as the chemical equilibrium deviates, reburn reactions gradually begin to occur on the "lean" side of the flame (as fuel radicals diffuse across the stoichiometric boundary), and the region of reburn reactions in terms of the composition of the gas mixture expands more than twofold. The contribution of reburn reactions on the lean side of the flame increases steadily and can reach 56% of the total reburn efficiency, which is of practical significance in systems with a high degree of combustion nonequilibrium. The main contributions to NO reduction on the lean side of the flame are reactions with CH (up to 75% via the GRI-Mech 3.0 mechanism) and reactions with HCCO (up to 80% via the Glarborg mechanism).

The results of a study examining the effect of a weak electric field on a Bunsen burner flame are presented, including the combustion of an aerosol consisting of water microdroplets in an air-methane mixture. Analysis of velocity fields obtained using a PIV system revealed changes in the laminar flame front propagation velocity when exposed to a weak electric field. Moreover, over a significant portion of the combustion front, the laminar front propagation velocity can be considered constant. The existence of an ion wind caused by the drift of negative charge carriers is confirmed. The introduction of water microdroplets into the fuel reduces the charge carrier concentration, indirectly evidenced by the fact that the effect of an electric field on combustion in this case leads to smaller changes in the flow structure ahead of the flame front.