Atmospheric and Oceanic Optics最新文献

Atmospheric monitoring from global satellite navigation systems is usually used for estimating the atmospheric integral water vapor and measuring zenith tropospheric delay of satellite radio signals and its gradient parameters characterizing atmospheric mesoscale irregularities with a high temporal resolution. Based on a sample of several hundred severe weather events corresponding to available observations at the nearest satellite stations in the Republic of Tatarstan and Moscow region located at latitudes 55°–56° N, the work shows a significant variability of these atmospheric parameters associated with convective severe weather events. The inhomogeneity of the field of the zenith tropospheric delay of satellite signals is shown to strongly increase under the conditions of a severe weather event, which is manifested in the increase in its gradient parameters and their fluctuations, as well as in the growth of the integral water vapor. The intensity of fluctuations of the integral water vapor most strongly changes if a station is located not further than 20 km from a severe event, which is explained by the size of convective cells. However, even if a station is spaced up to 200 km apart from a severe event, an increase in the atmospheric integral water vapor and the amplification of inhomogeneity as compared to long-term average data are observed.

There is considerable uncertainty about the methane emission from Arctic shelf seas. Methane fluxes in this region can be underestimated and play a significant role due to the large volume of gas contained in bottom sediments in the permafrost and gas hydrates. We analyzed the model sensitivity to the parameterization of gas exchange processes on the sea surface based on the numerical modeling of the transport of dissolved methane in Arctic seas. A dissolved methane transport model is included into the basic model of the ocean and sea ice SibCIOM developed at Institute of Computational Mathematics and Mathematical Geophysics, Siberian Branch, Russian Academy of Sciences. Methane emissions into the atmosphere were estimated with various parameterization of the gas exchange process in the “water–atmosphere” and “water–ice–atmosphere” systems with NCEP/NCAR reanalysis data. The uncertainty of the estimate of annual methane emission amounted to 6–12% when considering different dependencies of gas exchange on wind. The scheme which considers the ice cover has a more pronounced influence on methane flux calculations: the uncertainty increased to 50–130%. Parameterization of the relation between ice cover and gas exchange can have a great effect on the calculated methane fluxes and lead to underestimation of its emission from Arctic shelf seas.

A description of the designed automated complex is presented. The results of measurements of the content of species with different volatilities in six particle size ranges from 0.3 to 5 μm with artificial heating from 25°С to and 200°С (with an intermediate point at 100°) are discussed. The particle concentration was recorded by an optical counter. The instrumentation complex was tested in the period 2021–2023 in separate series of round-the-clock observations in different seasons. The photoelectric counter and integrating nephelometer measurements in December 2022 and March 2023 were compared. It has been shown that variations in the relative content of soluble sulfur compounds according to the counter data are in a good agreement with the variability of the values of the parameter of condensation activity. In general, the use of this method is hoped to make it possible to obtain additional information about the seasonal and diurnal variations in aerosol composition in the intermediate range of particle sizes.

This paper presents the results of an experiment on remote sensing of a smoke plume over a model fire with the use of a specialized lidar for detecting optical turbulence, which is based on the backscatter enhancement effect. Burning was 1600 m away, and the area of the model fire varied from 1, 9, and 25 m². During combustion, a lidar echo signal in the main receiving channel, which records aerosol scattering and the turbulent component, increased relative to an echo signal in the additional receiving channel, which records only the aerosol. The width of the smoke plume did not exceed 20 m; an increase in the main echo signal was observed immediately after the plume at distances of up to 600 m. In this experiment, a plume of warm smoke acted as a phase screen which changed the coherent structure of a laser beam. After the completion of intensive combustion, the temperature inside the plume rapidly decreased and the lidar recorded only the aerosol content. Appearance of two indicators in an echo signal, an increase in the aerosol concentration and strengthening of turbulence, clearly points out to a burning source. The lidar estimate of the structure characteristic of the refractive index (C_{n}^{2}) at an altitude of 10 m above the combustion focus was compared with data of AMK-03 ultrasonic meteorological station at an altitude of 3 m and results of simulation of a grass-roots fire published earlier.

The laser fragmentation/laser-induced fluorescence (LF/LIF) method is well known for its efficiency in detecting complex chemical compounds based on the fluorescence of their characteristic fragments. The method is applied, for example, to measuring the local content of nitrous acid and hydroxyl radicals in the atmosphere, visualization of intermediate stages of combustion processes, remote detection of substances in the gaseous state in the atmosphere and condensed state on surfaces, etc. We present for the first time the results of the experimental study of a possibility of remote excitation of LIF of characteristic photofragments of a substance in an aerosol state in the atmosphere. The organophosphorus compound triethyl phosphate (TEP) was used as the test substance. It has been shown that synchronized two-pulse laser irradiation of TEP aerosol particles and their PO-fragments (phosphorus oxide molecules) makes it possible to increase the efficiency of the LF/LIF process by approximately seven times compared to single-pulse laser exposure. It has been established that formation of PO-fragments of TEP aerosol under the laser irradiation at a wavelength of 266 nm has a decaying exponential character with a characteristic time of 192.6 ± 20.2 ns. In terms of the nature of the time dependence of the formation of photofragments, the results obtained are fundamentally different from similar measurements for other compounds in gaseous and condensed states and motivate further research that will contribute to the development of the LF/LIF method.

Aerosol nanoparticles play an active role in heterogeneous processes which change the optical and physicochemical properties of the atmosphere and the state of ecosystems and climate. Aerosol generation conditions, its geographical and seasonal features affect the microphysical characteristics of ultrafine aerosol. The work considers the first results of summer field observations of the microphysical characteristics of ultrafine aerosol particles in the near-surface air layer in the dry steppe zone of southern Russia in 2021 and 2022. Taking into account the synoptic and meteorological conditions, the daily variations in the concentration and size distribution of ultrafine aerosols (nucleation and Aitken modes and a transient subfraction) are studied, as well as their short-term variability. The permanent presence of Aitken particles at any time of a day and under any meteorological conditions is ascertained. Minimal concentrations of nucleation particles and Aitken particles are detected at night and in the early morning. The nucleation particle generation rate is typically the highest in the morning hours, when photochemical processes are active; this causes the morning maxima of concentrations of nucleation and Aitken particles. The concentration of transient subfraction particles increases during the nighttime. The features of the short-period variability of ultrafine aerosols are studied taking into account the general dynamics of daily aerosol generation and subsequent particle growth in the atmosphere, as well as through comparison with observations in other regions of the world. The results can be used for the study of the atmospheric composition and in chemical transport models to clarify the contribution of aerosols to the direct and indirect radiative effect and to climate change processes.

According to the IPCC-2021 Report on Climate Change, the atmospheric CO₂ and CH₄ concentrations have increased by around a quarter for the past 50 years. The CO₂ and CH₄ radiative forcing due to their concentration growth was calculated for mid-latitudes. The vertical profiles of temperature and humidity were taken from the ECMWF ERA-5 European reanalysis data. An effect of overlapping of H₂O absorption bands with CO₂ and CH₄ bands on the radiative forcing calculation results in the troposphere and stratosphere of midlatitudes with different water vapor content was studied by statistical methods. It was shown that absolute value of the CO₂ radiative forcing in the troposphere increases with the atmospheric water vapor content, whereas the CH₄ radiative forcing does not depend on the atmospheric total column water vapor.

Gaseous elemental mercury (GEM) is the predominant form of mercury in the atmosphere. As a result of deposition, it enters terrestrial and aquatic ecosystems, where it is further transformed into the ecotoxicant methylmercury. The work studies GEM in atmospheric air and total mercury in atmospheric precipitation in the Southern Baikal region. Sampling was carried out at Listvyanka monitoring station (51.9° N, 104.4° E) in 2022–2023. The concentrations of mercury in air was measured with a RA-915AM mercury gas analyzer (St. Petersburg, Russia); the concentration of total mercury in precipitation was determined by PND F 14.1:2:4.271-2012 method A (permanganate mineralization) technique. The measured concentrations were statistically analyzed. During the period under study, the concentration of GEM in atmospheric air averaged 1.61 ng/m³; the pair correlation coefficient was 0.47 between Hg⁰ and sulfur dioxide (SO₂) and 0.44 between Hg⁰ and nitrogen dioxide (NO₂); a strong positive correlation (>0.9) between Hg⁰, SO₂, and NO₂ was found in 12 cases. For each episode of mercury concentration above 2.0 ng/m³, back trajectories of air masses were calculated using the HYSPLIT model. The trajectory analysis also confirmed our assumption of a common type of sources of mercury and trace gases. The weighted average content of total mercury in precipitation is 44 ng/L, the median value is 29 ng/L, and the maximum is 282 ng/L. The results supplement the existing ideas about mercury content in the atmosphere of the Southern Baikal region and show the mercury content in atmospheric precipitation on the Baikal shore to be comparable with the results obtained in urban agglomerations of Nepal, Canada, Korea, and China despite the significant distance of the measurement site from large cities.

Desertified areas are the main source of dust aerosol. The emission and transport of dust aerosol in the near-surface layer of the atmosphere are markedly affected by electrification of the wind-sand flux. Electrical processes in a wind-sand flux have been studied experimentally. Based on data of synchronous measurements of the density of saltation electric currents and currents caused by transport of charged dust aerosol particles at heights of 4 and 12 cm in a desertified area in Astrakhan oblast, statistical characteristics of variations in the density and density moduli of these currents are calculated. It is shown that in a wind-sand flux in the height range from 4 to 12 cm, the density modules of saltation electric currents and currents caused by transport of dust aerosol decrease with height much more slowly (the logarithmic gradients are −0.025 and −0.07 cm⁻¹) than the concentration of saltating particles (the logarithmic gradient is −0.32 cm⁻¹). It is confirmed that the moduli of saltation electric current density correlate with each other and with the wind speed in the surface air layer more closely than the current densities themselves. The results obtained are of interest in developing models of dust aerosol emission in desertified areas.

Accurate measurements of the concentration of nitrous oxide, a potent greenhouse gas, in the Earth’s atmosphere are important for modeling the radiation balance of our planet. The work presents the measured broadening and shift coefficients of N₂O lines by air pressure at room temperature for 82 rovibrational transitions in the (00⁰2) ← (00⁰0) band; the rotational quantum number m varies from 3 to 54. The measurements were carried out with a Bruker IFS-125M Fourier transform spectrometer with a spectral resolution of 0.0056 cm⁻¹. The calculated line-broadening and shift coefficients were obtained using a semiclassical method modified by introducing a correction factor in the calculation scheme. Our parameters are compared with those presented in the literature and in modern spectroscopic databases. A vibrational dependence of the line halfwidths is revealed for the ν₃ stretching vibration.