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A more accurate characterization of the sources and sinks of methane (CH4) and carbon dioxide (CO2) in the vulnerable Arctic environment is required to better predict climate change. A large-scale aircraft campaign took place in September 2020 focusing on the Siberian Arctic coast. CH4 and CO2 were measured in situ during the campaign and form the core of this study. Measured ozone (O3) and carbon monoxide (CO) are used here as tracers. Median CH4 mixing ratios are fairly higher than the monthly mean hemispheric reference (Mauna Loa, Hawaii, US) with 1890–1969 ppb vs. 1887 ppb respectively, while CO2 mixing ratios from all flights are lower (408.09–411.50 ppm vs. 411.52 ppm). We also report on three case studies. Our analysis suggests that during the campaign the European part of Russia's Arctic and western Siberia were subject to long-range transport of polluted air masses, while the east was mainly under the influence of local emissions of greenhouse gases. The relative contributions of the main anthropogenic and natural sources of CH4 are simulated using the Lagrangian model FLEXPART in order to identify dominant sources in the boundary layer and in the free troposphere. On western terrestrial flights, air mass composition is influenced by emissions from wetlands and anthropogenic activities (waste management, fossil fuel industry, and to a lesser extent the agricultural sector), while in the east, emissions are dominated by freshwater, wetlands, and the oceans, with a likely contribution from anthropogenic sources related to fossil fuels. Our results highlight the importance of the contributions from freshwater and ocean emissions. Considering the large uncertainties associated with them, our study suggests that the emissions from these aquatic sources should receive more attention in Siberia.

The results of airborne measurements and statistical characteristics of mesoscale fluctuations of wind velocity, temperature, and concentrations of gas constituents at different heights of a stably stratified troposphere are presented. The measurements were carried out in September 2022 in the Arctic region of Russia with the aircraft laboratory Tu-134 “Optik.” The obtained spectra and structure functions of the fluctuations are interpreted with the theoretical model of formation of the spectrum of mesoscale wind velocity and temperature fluctuations described in the paper. The presence at high wavenumbers of a steep section in the obtained horizontal wavenumber spectra of the fluctuations of wind velocity and greenhouse gas concentration with a slope close to −3 is discussed. The fluctuation spectra along different slanted tracks of the aircraft crossing the tropospheric layer between altitudes of 1 and 9 km are also obtained and analyzed with the theoretical model.

Сlimate warming in the Arctic is several times faster than in other regions of the globe. This сan be the result of strengthening of feedbacks between climate and atmospheric composition. However, there are very few data on changes in the concentration of climatically active substances in this region. Therefore, to fill the gap in data on the vertical distribution of gas and aerosol composition of air over the Russian Arctic, an airborne survey of the atmosphere and water surface over all the Russian Arctic Ocean seas was performed with use of the Tu-134 Optik aircraft laboratory in September 2020. This paper analyzes the spatial distribution of gas and aerosol composition in the Arctic troposphere. It is shown that during the experiment, the CO 2 mixing ratio increased in the near-water and boundary layers and decreased in the free troposphere from west to east. The methane content in the near-water layer decreased in the same direction. Concentrations of CO, NO X , and SO 2 in the Russian Arctic were very low, which was typical for remote background areas. All aerosol fractions also showed a decrease in their content from west to east.

The article presents the results of studies of the chemical composition, crystal structure, lattice parameters, microstructure, the valence state of the europium ion (at 300 K), electrical resistivity, and differential thermopower (6–400 K) of samples in the Eu(Cu1 − xAgx)2Si2 (0 ≤ x ≤ 1) substitutional solid solutions. A transition of the europium ion from the valence-stable state of Eu2+ in EuAg2Si2 to the state of intermediate (homogeneous) valence (IV) of the europium ion in EuCu2Si2 with an effective valence ϑeff = 2.41 (300 K) has been initiated by a successive replacement of silver atoms by copper atoms. With appropriate sample compositions, the transition passes through a Kondo-type state. The research subject is the patterns of transformations (when the composition of the sample changes), the electronic state, and, accordingly, the electronic transport properties. The simultaneous coexistence of europium ions in different electronic states is assumed. The substitutional solid solution Eu(Cu1 − xAgx)2Si2 (0 ≤ x ≤ 1) exhibits properties related to the competition between the state of the Kondo system, intermediate valence (IV), and magnetic ordering.

The ongoing global warming leads to the need in continuous monitoring of greenhouse gas concentrations and the magnitude of their fluxes. Gas exchange between terrestrial ecosystems and the atmosphere is mainly measured using eddy covariance, gradient, and chamber methods. This work compares greenhouse gas fluxes measured using the eddy covariance technique onboard an aircraft laboratory and with the gas analysis system and meteorological sensors at ZOTTO observatory. Instrument suites of the aircraft laboratory and the observatory are described. The comparison results showed that CO2 and CH4 fluxes measured by two different methods at the same altitudes coincide in sign, are close to each other in the value for carbon dioxide, and differ by up to 2 times for methane. The results are of interest to specialists who study greenhouse gas fluxes using the eddy covariance method.

Eight surface observation sites providing quasi-continuous measurements of atmospheric methane mixing ratios have been operated since the mid-2000's in Siberia. For the first time in a single work, we assimilate 1 year of these in situ observations in an atmospheric inversion. Our objective is to quantify methane surface fluxes from anthropogenic and wetland sources at the mesoscale in the Siberian lowlands for the year 2010. To do so, we first inquire about the way the inversion uses the observations and the way the fluxes are constrained by the observation sites. As atmospheric inversions at the mesoscale suffer from mis-quantified sources of uncertainties, we follow recent innovations in inversion techniques and use a new inversion approach which quantifies the uncertainties more objectively than the previous inversion systems. We find that, due to errors in the representation of the atmospheric transport and redundant pieces of information, only one observation every few days is found valuable by the inversion. The remaining high-resolution quasi-continuous signal is representative of very local emission patterns difficult to analyse with a mesoscale system. An analysis of the use of information by the inversion also reveals that the observation sites constrain methane emissions within a radius of 500 km. More observation sites than the ones currently in operation are then necessary to constrain the whole Siberian lowlands. Still, the fluxes within the constrained areas are quantified with objectified uncertainties. Finally, the tolerance intervals for posterior methane fluxes are of roughly 20 % (resp. 50 %) of the fluxes for anthropogenic (resp. wetland) sources. About 50–70 % of Siberian lowlands emissions are constrained by the inversion on average on an annual basis. Extrapolating the figures on the constrained areas to the whole Siberian lowlands, we find a regional methane budget of 5–28 TgCH4 for the year 2010, i.e. 1–5 % of the global methane emissions. As very few in situ observations are available in the region of interest, observations of methane total columns from the Greenhouse Gas Observing SATellite (GOSAT) are tentatively used for the evaluation of the inversion results, but they exhibit only a marginal signal from the fluxes within the region of interest.

Clear air turbulence (CAT) constitutes the highest danger for aviation in the free atmosphere in the altitude range 6–12 km. Intermittence and random localization of CAT in a quiet surrounding air flow significantly restrict possibilities of its forecasting. Creation of systems for remote detection of turbulent zones becomes especially topical with allowance for climate changes and increase in the probability of CAT appearance. Results of turbulence sounding by the BSE-5 UV lidar from the Optik Tu-134 aircraft laboratory are presented. The in-flight experiment was conducted in September 2022 as part of the Arctic exploration program. The lidar recorded zones of moderate turbulence in the lower troposphere where the probability of turbulence is maximum; isolated cases of CAT were also recorded at an altitude of 9 km. The turbulent lidar can be used in practice for remote detection of turbulent zones at altitudes where most commercial flights are carried out. The prospects of ground-based application of the turbulent lidar for solving aviation safety problems during flights in the lower troposphere are also shown. The results of the BSE-5 lidar sounding in winter, when an increase in the intensity of turbulence in the 0.4–1.6-km layer was recorded during the passage of a cold front, are presented.

We present the results of comparative characterization of fractional composition of surface aerosols in the period of summer vegetation and winter dormancy of woody plants in the boreal zone of Western Siberia. The article presents statistics on the size distribution of aerosol particles at the Fonovaya Observatory of IAO SB RAS (Tomsk Region) from July 1, 2022, to June 30, 2023. The analysis of the ratios of aerosol fractions revealed a paradoxical situation, where the number concentration of aerosol particles 0.3–2.0 μm diameter turned out to be significantly higher in winter than in summer. A phenomenological model is suggested which describes this effect as a manifestation of the action of radiometric forces.

—Based on retrospective comparison with the data of ground-based spectroscopic measurements carried out in Peterhof by St. Petersburg State University (SPbSU) and aircraft measurements carried out in the area of the Novosibirsk Reservoir by the Zuev Institute of Atmospheric Optics in 2019–2022, results of application of a new version of the regression technique for determining the total carbon dioxide XCO2 content (the mole fraction of atmospheric CO 2 in dry air) by measurements of the IKFS-2 infrared Fourier spectrometer of the Meteor-M No. 2 Russian meteorological satellite are analyzed. A description of changes made in the technique to improve the accuracy of satellite estimates is given. For example, to compensate for the influence of changes in IKFS-2 characteristics during a long flight on the XCO2 estimates, they are calibrated based on the results of ground measurements from the NOAA observatory at Mauna Loa volcano (the island of Hawai’i). After calibration and filtering of cloud scenes, the divergence of satellite estimates from ground and aircraft measurements is characterized by a mean square deviation of ~4 ppm or 1% of the total XCO2 content. To speed up the adaptation of the regression algorithm for XCO2 estimation to the IKFS-2 data, it is proposed to use on the new satellites XCO2 estimates from the TCCON ground-based network in addition to the contact measurements of CO 2 concentrations. Also, it is reasonable to use in the regressions the thickness of the cryodeposit on the IKFS-2 photodetector glass as another predictor characterizing the state of the instrument.

The change of the global climate is most pronounced in the Arctic, where the air temperature increases 2 to 3 times faster than the global average. This process is associated with an increase in the concentration of greenhouse gases in the atmosphere. There are publications predicting the sharp increase in methane emissions into the atmosphere due to permafrost thawing. Therefore, it is important to study how the air composition in the Arctic changes in the changing climate. In the Russian sector of the Arctic, the air composition was measured only in the surface atmospheric layer at the coastal stations or earlier at the drifting stations. Vertical distributions of gas constituents of the atmosphere and aerosol were determined only in a few small regions. That is why the integrated experiment was carried out to measure the composition of the troposphere in the entire Russian sector of the Arctic from on board the Optik Tu-134 aircraft laboratory in the period of ​​​​​​​4 to 17 September of 2020. The aircraft laboratory was equipped with contact and remote measurement facilities. The contact facilities were capable of measuring the concentrations of CO2, CH4, O3, CO, NOx​​​​​​​, and SO2, as well as the disperse composition of particles in the size range from 3 nm to 32 µm, black carbon, and organic and inorganic components of atmospheric aerosol. The remote facilities were operated to measure the water transparency in the upper layer of the ocean, the chlorophyll content in water, and spectral characteristics of the underlying surface. The measured data have shown that the ocean continues absorbing CO2. This process is most intense over the Barents and Kara seas. The recorded methane concentration was increased over all the Arctic seas, reaching 2090 ppb in the near-water layer over the Kara Sea. The contents of other gas components and black carbon were close to the background level. In bioaerosol, bacteria predominated among the identified microorganisms. In most samples, they were represented by coccal forms, less often spore-forming and non-spore-bearing rod-shaped bacteria. No dependence of the representation of various bacterial genera on the height and the sampling site was revealed. The most turbid during the experiment was the upper layer of the Chukchi and Bering seas. The Barents Sea turned out to be the most transparent. The differences in extinction varied by more than a factor of 1.5. In all measurements, except for the Barents Sea, the tendency of an increase in chlorophyll fluorescence in more transparent waters was observed.