Volume 60, Nº 5 (2024)

The paper is devoted to the study of the characteristics of internal waves in the Kara Sea and their interaction with the atmosphere, in particular, their influence on the turbulent momentum and heat fluxes in the surface layer of the atmosphere. The direction and horizontal velocity of propagation of short-period internal waves in the Kara Gate Strait were calculated. Cross-spectra of mesoscale fluctuations of water temperature at the sea surface, at depths of 10 and 20 m, and meteorological parameters at 22 m height were analyzed. Common spectral maxima at periods characteristic of the trapped internal gravity modes propagating in the thermocline layer and atmospheric gravity modes in the stably-stratified layer of the lower troposphere are revealed. A possible mechanism of influence of the observed gravity modes in the thermocline layer on mesoscale fluctuations of meteorological parameters (with periods from 10 min to several hours) and turbulent fluxes of momentum, apparent and latent heat in the surface layer of the atmosphere is proposed.

The paper presents the results of measurements of the optical characteristics of the aerosol particles using a solar photometer and nephelometer from 2016 to 2021, obtained at the atmospheric monitoring station in Peterhof (59.88°N, 29.83°E). The measurements were compared with the MERRA-2 reanalysis data. It is shown that inter–seasonal variability is observed in the region, characterized by low values of the Angstrom exponent in winter and high values in the warm season. The backscatter fraction has a similar but less pronounced seasonal cycle. The average value of the turbidity coefficient for the period is less than 0.10, which makes it possible to determine the observation station as a background one. Using the HYSPLIT model, the origin of air masses forming the atmospheric air state at the observation station was determined in cases of realization of the limiting values of the measured scattering coefficients (< 10 and > 70) and the Angstrom exponent (< 1). Air masses coming from the north-west direction correspond to clean and humid air from the marine area and are manifested in the minimum values of the measured parameters. The maximum values of the scattering coefficient are associated with fine aerosol coming in the atmosphere both from regional emissions sources (urban pollution from the territory of St. Petersburg) and as a result of transboundary transport from southwestern directions.

Assessment of air quality in the industrial cities is of the high attention, especially in the regions sensitive to the ecological and climate changes. Study of atmospheric aerosol loading carried out in the Novy Urengoy city during summer- autumn of 2023. Particle number concentration, mass concentration of particle with a size less than 10 µm (PM₁₀) and 2.5 µm (PM_2.5) as well as black carbon (BC) measured by the mobile Aerosol Complex. The portion of fossil fuel combustion FF% and biomass burning (BB%) estimated using the aethalometer model. BC concentrations increased during pollution episodes recorded at the end of June (I) and July (II), in the beginning of August (III) and September (IV), doubled on average in comparison with the level of urban emissions. During the episode IV of maximum pollution ВС concentration and its impact to PM_2.5 increased 4 and 5 times, respectively. At that time, portion of fossil fuel combustion FF% approached 96%. Cluster analyses of ВС dependence on the wind speed and direction revealed the sector of high concentration source. FF% indicated the direction of the emissions from the biggest industrial enterprise of Urengoy oil and gas condensate field. Wildfire plume identified by ВВ% from the south of Siberia.

We study the reaction of the Black Sea upper layer, and in particular the cold intermediate layer (CIL), to intense wind forcing during cold air intrusions (CAIs) in winter. Using atmospheric reanalysis ERA5 and marine reanalysis Copernicus, we obtained joint distributions of surface wind speed and water temperature differences at various depths for the period of 2000–2020. It is shown that reaction time of the sea upper layer to such extreme weather event as CAI is about 2 days. Also, it is shown that CAI influence extends to great depths, up to 60–70 m. Using coupled mesoscale sea-atmosphere model, we investigated the cooling mechanisms of the sea upper layer during the CAI case in January, 23–25, 2010. Two sensitivity experiments with suppressed air-sea interaction were performed. In the first experiment, sensible and latent heat fluxes from the sea surface were switched off. In the second experiment, wind shear stress at the sea surface was switched off. It is shown that the main reason for temperature decrease in the upper mixed layer was sea surface cooling due to sensible and latent heat fluxes. And the mechanism of deep cooling, that penetrates to the pycnocline, was vertical turbulent mixing caused by wind waves breaking and shear instability. In the first experiment, temperature decrease was insignificant; it was caused mainly by the entrainment of cold water from the CIL through the lower boundary of the mixed layer. In the second experiment, temperature decrease was as significant as in the control run. It is shown that after switching off wind shear stress in the second experiment turbulent mixing in the upper quasi-homogeneous layer of the sea changed fundamentally. In order to compensate the decrease of turbulence intensity and provide the same vertical heat flux as in the control run, the spatial vertical scale of turbulent eddies increased.

The paper presents the results of a comparison of the atmospheric reanalysis of the 20th century ERA-20C and NOAA-CIRES-DOE 20th Century Reanalysis with the data of meteorological observations made during the forced drift of the schooner «St. Anna» in 1912–1914 in the Arctic. Synchronous time series of atmospheric pressure, air temperature and wind were compared using correlation analysis and estimates of mean error (bias) and root-mean-square error (RMSE). To compare wind data, specialized techniques for comparing vector series were used. For all meteorological characteristics, the NOAA-CIRES-DOE 20 version 3 reanalysis shows the highest values of correlation and the lowest RMSE values. The minimum mean error values for atmospheric pressure and air temperature data are shown by the ERA-20C reanalysis. It has been established that there is a systematic deviation of approximately 12–15° between the wind measurement data and the reanalysis wind.