Vol 60, No 4 (2024)

The paper presents the results of an analysis of the influence of submesoscale internal gravity waves (IGWs), registered with the help of a sodar in the atmospheric boundary layer, on turbulence characteristics measured in the surface layer. Data obtained in rural areas in the Moscow region were used.Two types of IGW were identified visually on sodar echograms: internal gravity-shear waves (IGSW) of the Kelvin-Helmholtz wave type and buoyancy waves (BW). For 28 episodes of IGSW and 10 episodes of BW, based on the data of eddy covariance measurements carried out with an ultrasonic thermometer-anemometer located on a mast 56 m high, turbulent kinetic energy, as well as heat and momentum fluxes were calculated. Alterations of these characteristics accompanying the passage of wave trains were investigated, particularly, quantitative estimates were made, and degree of influence of IGSW and BW on the turbulence was compared.

The Southern Ocean plays a key role in the global circulation of the World Ocean. The Weddell Gyre, being one of two gyres that determine the large-scale dynamics of the Southern Ocean, makes a significant contribution to the global thermohaline circulation. In this regard, the study of the dynamics and structure of waters in the Weddell Sea seems very relevant for improving our understanding of the processes occurring in the World Ocean. In this work, based on an array of data on current velocities from moorings collected from an open source (Pangaea), the vertical structure of currents on a slope in the western part of the Weddell Sea (northwestern and southern parts) was studied. The main result is the intensification of the current in the bottom layer identified, based on the mean velocities calculated over the period of measurement, which, apparently, is a characteristic feature of the Weddell Gyre for both its western and southern branches. An increase in velocities in the bottom layer at individual moorings previously noted in separate works was confirmed and shown based on an array of data on current velocities from 108 sensors at 37 moorings on the continental slope in the northwestern and southern parts of the Weddell Sea.

Results of analysis of long-term trends and interannual variations of the NO₂ content in the atmosphere according to measurements with the Ozone Monitoring Instrument (OMI) aboard the EOS-Aura satellite in 2004–2020 are compared to the results of a similar analysis of the NO₂ content derived from independent spectrometric twilight NO₂ measurements by zenith-scattered solar radiation at stations of the Network for the Detection of Atmospheric Composition Change (NDACC)). According to both the data, seasonally dependent estimates of linear NO₂ trends and variations of the NO₂ content under the influence of the 11-year cycle of solar activity and large-scale circulation factors such as the Arctic and Antarctic Oscillations, variations in ocean surface temperature in the Niño 3.4 zone, and the quasi-biennial oscillation in zonal wind in the equatorial stratosphere have been obtained. In general, a good qualitative and, in some cases, quantitative correspondence between estimates of interannual variations of NO₂ has been obtained. For interannual variations of stratospheric NO₂, not a bad correspondence between estimates based on satellite and ground-based data has been obtained on average for all stations, but the correspondence between trend estimates is noticeably worse. The best correspondence between the analysis results has been obtained for Zvenigorod station. For stratospheric NO₂, it was noted in 80–90% of cases, and the correspondence for tropospheric NO₂ is practically 100%.

Estimates of methane emissions in the warm season from the Zeya reservoir, one of the biggest hydropower facilities that affects Russia’s carbon balance, were obtained for the first time based on the field measurements of methane concentrations in water and methane fluxes from the water surface. During expeditionary investigations conducted in September 2021 and July 2022, field data were collected. It was feasible to create the aquatory zoning and learn more about the water body’s thermal, oxygen, and chemical structure based on hydrological and chemical investigations. In conjunction with zoning, a digital elevation model of the Zeya reservoir’s bed was created, allowing calculating the reservoir’s total methane emission. It has been determined that marshy tributaries and shallow aquatories, where organic matter flows from the banks, are the primary sources of organic matter and methane. During the summer, when shallow waters are heated, there is a significantly larger overall methane flux from the reservoir’s surface. Methane emission coefficients from the Zeya Reservoir (8.6–17.2 kg CH₄/ha) are consistent with those from surface-based boreal reservoirs that are provided in the supplements to the 2019 IPCC Guidelines.

The formation of methane fluxes in the Rybinsk reservoir and the variability of its content in water were investigated during several field campaigns on the reservoir in different seasons. The Rybinsk reservoir is a very large, relatively shallow, low-flow, mesotrophic-eutrophic, morphologically complex basin-valley type reservoir with perennial flow regulation, created on the Upper Volga in 1941. In total, water and air sampling was carried out at 71 stations to determine methane concentration, which was combined with measurements of water column characteristics . As a result, a network of reference stations was established, where regular measurements are made, as well as additional stations in the water area and river estuaries. For control purposes, water samples were taken at the hydroelectric power plant units and downstream of the Sheksninskaya HPP dam, placed within the Rybinsk city. In general, the Rybinsk reservoir is characterised by relatively low methane concentrations - at most stations the average content of dissolved CH4 in water does not exceed 20 µl/l. The lowest concentrations were observed during the winter period. Methane fluxes from the surface of the Rybinsk reservoir vary from 4 to 718 mgC-CH4 m-2 day-1. Specific fluxes in summer period are larger than those measured in autumn, also in summer the spatial variability of the measured fluxes is more significant. Flux values depend on reservoir stratification, oxygen content in water, organic matter in bottom sediments and other factors. Methane degassing through the dam is significantly less than the fluxes from the surface.