A.M. Obukhov Institute of Atmospheric Physics

The paper is devoted to the comparative analysis of the responses of the minimum frequency of reflections on ionograms (fmin) and the mesosphere-low thermosphere (MLT) temperature to the sudden stratospheric warmings (SSWs) in 2008, 2009, and 2013. The experimental basis for the research is the fmin measurements with the DPS-4 digital ionosonde in Irkutsk, the Aura/MLS satellite data on the atmospheric temperature at different altitudes, and the data on the rotational temperature of the hydroxyl molecule obtained from spectrometric measurements at ~100 km from Irkutsk. Comparative analysis of the behavior of fmin and the MLT temperature has revealed both a case of high correlation (SSW 2008) and no correlation (SSW 2009), along with an intermediate variant during the SSW 2013. The paper discusses the reasons for the different correlations between the analyzed parameters.

The results of verification of the aerodynamic method for calculating turbulent heat fluxes between the glacier and the atmosphere using the eddy covariance method are presented. The experiment was conducted on Aldegondabreen, Svalbard, in August 2022. Comparison of the methods showed a high agreement between the fluxes estimated by the two methods (R2 = 0.7), but the aerodynamic method underestimated the flux (with a mean error of 14%). The eddy covariance method allowed us to estimate the aerodynamic roughness length parameter for Aldegondabreen z0m = 0.8 mm, and the thermal roughness length z0h = 0.08 mm. The uncertainty analysis of the aerodynamic method revealed systematic errors related to the wind flow direction. The coefficient of proportionality was 0.67–0.70 for the wind direction along the glacier slope and 0.98 for the wind direction perpendicular to the glacier slope. Mean values of heat fluxes during the ablation season for the period 1991–2020 were calculated for Aldegondabreen: the shortwave balance is 72.6–113.8 W m–2; the longwave balance is 14.5 W m–2; the turbulent fluxes of sensible and latent heat determined by the aerodynamic method are 20.5 and about 1 W m–2, respectively. Thus, even allowing for a systematic method error of 14% (~3 W m–2), the total turbulent heat exchange of 24.5 W m–2 was lower than the mean estimates for the shortwave balance.

This study presents the results of numerical experiments of neutrally-stratified turbulent flows over idealized urban surfaces using the Large-Eddy Simulation (LES) model. It is shown that the turbulent length scales necessary for the formulation of multilayer local one-dimensional Reynolds-Averaged Navier–Stokes (RANS) models of the urban canopy are related to the spatial spectra of turbulence. An algorithm based on the application of the Taylor frozen turbulence hypothesis is proposed to compute an analog of the spatial velocity spectrum inside an urban layer containing objects (“buildings”). The dependence of length scales on the morphological characteristics of the urban surface gets a qualitative explanation.

The results of experimental studies of the propagation of a nonlinear acoustic wave (NAW) in the surface layer of the atmosphere are analyzed. The influence of the underlying surface and vegetation on the waveform, as well as on its amplitude and width of the frontal region, is considered. A large-scale effect of the interaction of a NAW with vegetation is revealed. It is shown that the expansion of the front region of the wave obeys the law of energy similarity. The necessity of searching for a mechanism that causes such a character of wave development is noted.

The source region of a turbulent flux from a surface or the coverage area when measuring from towers is subject to spatial and temporal variability. The need for accurate estimation of the source region of the measured flux or the footprint has significantly increased with the establishment of stations for long-term monitoring of turbulent exchange over forests and other heterogeneous landscapes and the creation of observation networks for determining the intensity of matter and energy exchange between ecosystems and the atmosphere (FLUXNET, AsiaFlux, RuFlux, and others). The footprint plays a crucial role in optimizing the instrument placement, interpreting time series of measured fluxes, analyzing the variability of fluxes in response to changes in the underlying surface, and estimating the quality of the data collected. However, estimating the footprint remains challenging due to the diversity of the studied fluxes and concentrations of substances. This paper provides an overview of available methods for modeling footprints and discusses their advantages and disadvantages. It also identifies current challenges and ways to improve existing approaches.

The morphology and composition of aerosol particles determine their activity in atmospheric heterogeneous processes and affect the radiation and chemical properties of the atmosphere. However, there is still insufficient information about the morphological characteristics of atmospheric aerosols. This work studies mineral composition of dust aerosol particles and identify natural and anthropogenic components in aerosol composition in the surface air layer in Moscow metropolis in winter. Microparticles containing a lot of potentially toxic elements, such as heavy metals and metalloids of anthropogenic or mixed origin, were found. Several groups of metal-containing microparticles in near-surface aerosols were identified, the most common of which were: (1) sulfates (mainly Ba and Sr); (2) sulfides (Fe, Sb, and Pb); (3) oxides (Fe, W, Cu, As, Cd, and Pb); (4) intermetallides (Pb–Sn–Zn, Pb–Zn, Cu–Zn, Cu–Pb, Te–Sb–Al–Bi, and Fe–Ni–Cu–Sn–Fe–Cr–Ni); (5) native metals (Pb, Zn, Ni, Te, Fe, Zr, and W). The distributions of different elements over the surface of a filter with an aerosol sample was estimated. It was found that most of microminerals in dust particles were in the calcium phase, and to a lesser extent, in silicate and aluminosilicate phases. The results complement information on the morphology and micro-mineral composition of aerosols in the near-surface air of a megalopolis and can be useful both for clarifying the role of aerosol particles in atmospheric heterogenic processes which change the climate and for solving applied environmental problems.