Atmospheric and Oceanic Optics最新文献

Aerosol particles which are generated in the atmosphere during photooxidation of organic compounds have reactive functional groups on their surfaces, which can be responsible for biological action of the organic aerosols. This work studies the kinetics and mechanism of atmospheric photonucleation of o-dichlorobenzene, which is a model of chlorinated aromatic hydrocarbons known for their environmental resistance, and the effects of water vapor and hydrogen peroxide on the yield and composition of aerosol products. The concentrations and sizes of aerosol particles were measured using a diffusion spectrometer of aerosol; the composition of gas and aerosol products of photonucleation was determined by high-performance liquid chromatography and gas chromatography-mass spectrometry. The formation mechanisms of identified products were determined based on the rate constants of elementary chemical reactions. It is shown that atmospheric photonucleation of dichlorobenzene does not result in photochemical generation of ozone in the surface air layer; quite contrary, dichlorobenzene photolysis products promote ozone destruction. The contribution of emissions of chlorinated aromatics into generation of organic aerosol in urban air is qualitatively estimated. The presence of reactive functional groups in the aerosol products enables us to assume negative biological action of the aerosol. The results can be used to model photochemical processes in polluted urban air.

The analysis of statistical properties of aerosol density fluctuations at civil aviation flight altitudes can serve a starting point for the study of the random component of wind velocity field. This work analyzes fluctuations of the power of a scattered signal measured by an airborne lidar in the DELICAT (DEmonstration of LIdar based Clear Air Turbulence detection) project experiment. A new technique for the study of aerosol clouds based on 2D Fourier transform is introduced. Flight segments with constant aircraft altitude, direction, and speed were selected for the analysis. A signal was considered in the coordinate system where the distance from the aircraft to a scattering volume is plotted along the abscissa and aircraft path relative to an air mass is plotted along the ordinate. In these coordinates, aerosol clouds appear as stripes inclined at an angle of 45°. Spatial spectra of aerosol density fluctuations are derived. 2D spectra have a peak in the vicinity of the main diagonal of the frequency plane for regions with aerosol; their diagonal cross sections are equal to estimates of 1D spatial spectra of aerosol concentration fluctuations within the following approximations: (1) clouds are motionless on a time scale of about 1 min, (2) variations in the sounding line direction are negligible. The slope of 1D spectra was estimated. The results can serve as a basis for studying the random component of wind velocity fields.

The onsets of polar stratospheric cloud (PSC) formation and chlorine activation are so far considered to be the temperature threshold of formation of nitric acid trihydrate T_NAT, below which the HNO₃ concentration sharply increases in PSC particles. In this paper, the data on the temperature, ozone mixing ratio, and nitric acid (HNO₃) mixing ratio in the Arctic stratosphere from the Aura MLS observations are used to calculate the minimal temperature, maximal negative deviations of ozone concentration from multiyear average, and maximal nitric acid (HNO₃) mixing ratios and total columns at four Arctic sites: Eureka, Canada (EUR); Ny-Ålesund, Norway (NAD); Thule, Greenland (THU); and Resolute, Canada (RES). The maximal HNO₃ concentrations decrease throughout the winter until late February at all observation sites under study due to condensation of gas-phase HNO₃ on PSC particles. The mixing ratios start to grow after return of sunlight to polar latitudes due to PSC sublimation and HNO₃ export from peripheral areas of the vortex during its deformation. The years, chosen for analysis (2010/2011, 2019/2020, 2020/2021, 2021/2022), cardinally differed in the stratospheric dynamics and in the state of ozone layer during winter and spring in the Arctic. Our results can be helpful for understanding the time dynamics of the HNO₃ mixing ratio in the winter-spring stratosphere of the Arctic and its role in the chemical ozone destruction.

Soot aerosol particles (black carbon) significantly contribute to atmospheric warming since they effectively absorb radiation in a wide wavelength range; along with greenhouse gases, they play an important role in the climate change. This work makes a critical analysis of the hypothesis of volcanogenic soot in the stratosphere (a possibility of producing black carbon nanoparticles by Plinian volcanic eruptions and their casting to high altitudes). Features of thermal decomposition of methane and origination of reduced carbon in a two-phase gas-ash volcanic column are discussed. Known data on the detection of carbonaceous particles in the atmosphere, their properties, and possible but not yet confirmed connection with strong volcanic eruptions are reviewed. The discovery of different reduced carbon forms in ashes of modern volcanic eruptions in Kamchatka (the phenomenon of volcanic carbon paragenesis) is commented on. Energy competition between two ways of formation of reduced carbon in the forms of soot nanoparticles and carbon products strongly mechanically bonded to pyroclastic material is discussed. The results can be useful in atmospheric aerosol physics and climatology for analyzing main sources of black carbon in the atmosphere.

The problem of atmospheric air pollution by fine particulate matter (PM_2.5) in large industrial centers during winter is one of the most acute environmental threats affecting the life expectancy and quality of population. The study examines the processes of temperature inversion layer formation and its impact on atmospheric PM_2.5 in Krasnoyarsk during the winter months of 2022–2024 based on data from a monitoring network, which measures air temperature, atmospheric pressure, wind speed and direction, PM_2.5 concentration, and cloud cover, and data from an MTP-5 profiler, which determines the vertical distribution of atmospheric temperature. The multi-hour and multi-day regimes of radiation and advective inversions are analyzed. The necessary and sufficient conditions for their occurrence are established. The statistical dependences of PM_2.5 concentration on the category and intensity of inversions are derived. The results can be used in short-term forecasting of temperature inversions and the associated periods of high PM_2.5 air pollution in the city of Krasnoyarsk.

This work presents a short-range experimental characterization of underwater pulsed laser imaging using a free-running CCD camera operating in frame-based acquisition mode under controlled laboratory conditions. Unlike time-gated imaging systems, the proposed approach relies on asynchronous acquisition and post-processing-based frame selection and is intended for preliminary experimental study rather than direct alternative to gated imaging. The system performance is estimated in terms of signal-to-noise ratio (SNR), analytical contrast-to-noise ratio (CNR), and image-based contrast-to-noise ratio (IB-CNR). Experiments were conducted in a 1.2 m water tank, which limits light propagation range, under varying turbidity conditions and target properties. Results indicate that imaging performance strongly depends on water attenuation and object characteristics such as reflectivity and surface texture. In the configuration under study, turbid water can be associated with apparent changes in relative contrast for reflective targets, which reduces fine spatial detail visibility in low-reflectivity textured objects; in contrast, clear water better preserves high-frequency information. The study confirms the relevance of frame-based CCD acquisition for exploratory underwater imaging analysis and emphasizes that comparisons with time-gated systems are primarily model-based rather than experimentally validated and should not be interpreted as physically equivalent.

The problem of air pollution in Crimea is of interest due to its geographical characteristics and resort use. Experimental studies on the composition and temporal variability of aerosols in the surface air layer were conducted in the southeastern part of the Crimean Peninsula at the background environmental monitoring station of Vyazemsky Karadag Scientific Station—Nature Reserve, Branch of the Institute of Biology of South Seas, from March 21 to June 17, 2020. For the first time, data are presented on temporal variations in the daily average mass concentration of aerosol, chemical elements in its composition, and aerosol particles of 0.15–1.5 and 0.2–5.0 µm in size. Concentrations of 25 selected chemical elements are determined. The analysis is carried out depending on the direction of arrival of air masses. The elemental composition of the aerosol is compared with its size distribution, meteorological conditions, and the direction of long-range transport of air masses. The size of particles transporting heavy metals and metalloids (Zn, Mo, Cd, Pb, Bi, Se, Sn, and Sb), as well as elements of global origin is determined. The elements S, Cu, and Hg for which no significant correlation with the particle size was found, are likely of mixed origin due to competition between natural and anthropogenic sources in different periods. The results characterize the aerosol parameters during the spring–summer period in the eastern part of Crimea and are of interest to specialists involved in environmental monitoring in the resort and recreation area.

Seasonal and long-term variations in the atmospheric content of greenhouse gases is determined by their sources and sinks, which can be identified from the analysis of isotopic composition of these gases. This analysis can also help to understand the current upward trends in greenhouse gas concentrations on a regional scale. Based on continuous observations of atmospheric CO₂ and CH₄ and carbon isotope composition of their molecules at the Fonovaya observatory (Tomsk region) in 2022–2024, we estimate the ranges of background values and seasonal patterns of carbon isotope ratios δ¹³C–CO₂ and δ¹³C–CH₄ in the atmosphere above the southern taiga zone of Western Siberia. The daytime means (01–05 pm) of δ¹³C–CO₂ and δ¹³C–CH₄ ranged from −9.2 to −5.7‰ and from −51.7 to −46.5‰, respectively. The analysis of background values revealed a sharp minimum in CO₂ concentration and a maximum in δ¹³C–CO₂ in summer, which indicate active uptake of ¹²CO₂ by regional terrestrial ecosystems. Winter values of CO₂ concentration and δ¹³C–CO₂ are consistent with data from other greenhouse gas monitoring stations in the Northern Hemisphere. The pattern of seasonal variations in atmospheric CH₄ mixing ratios and δ¹³C–CH₄ values in the region under study indicates that the winter maximum in CH₄ content is driven by anthropogenic factors, while the summer maximum, by the predominance of biogenic methane emissions from Western Siberian wetlands. Using the Keeling plot method, source/sink signatures which affect changes in atmospheric CO₂ and CH₄ concentrations in the region under study were determined for each month of the year. The results can be used for analyzing and interpreting long-term observations of greenhouse gases in Siberia.

Methods for numerical interpretation of satellite measurements of nitrogen dioxide with the use of a model for reconstructing long-term regional pollution from a high-altitude point source of atmospheric emissions are discussed. The model is based on asymptotic representations of impurity concentration fields at significant distances from a source. Satellite measurements of nitrogen dioxide content in the region of the Gusinoozersk State District Power Plant (SDPP) were numerically analyzed. A high level of agreement was observed between satellite observations and model concentration fields for nitrogen dioxide emissions from SDPP pipes in the southwest and northwest directions. The analysis revealed the presence of significant nitrogen dioxide background concentrations caused by emissions from remote sources. The developed model also enables estimating the contributions of additional sources to NO₂ concentration fields. The results can be used for estimating air pollutant emissions from thermal power plants from satellite data.

Laser-induced plasma diagnostics in aerosols is complicated by plasma inhomogeneity. In this work, the electron density of laser-induced plasma generated in liquid-droplet aerosol is evaluated based on Ba II 455.4, Na I 589, Al I 396.2, Ca II 393.4, and Fe I 542.4 nm emission lines for the case of using equipment on mobile carriers. It is found that the electron density is minimal for the Ba II line and maximal for the Na I line; the difference in the values reaches almost an order of magnitude, which is attributed to differences in the diffusion lengths of the elements. It is experimentally shown that the plasma electron temperature weakly depends on time in the range of 2–4 μs at exposure times of 40 and 150 μs. It is confirmed that recombination pumping of the upper levels of the transitions under study insignificantly affects the intensity of the analytical lines. Based on the analysis of the rate constants of excitation from the ground state, the limit of detection is found to be the worst for the Al I 396.2 nm line. The results of the work are in demand in emission spectral analysis of aerosols.