Home – Home – Jornals – Atmospheric and Oceanic Optics 2024 number 9

Three-dimensional transport and transformation models make it possible to take into account the vertical heterogeneity of atmospheric processes. However their use requires setting a large number of parameters and significant computing resources, especially when solving inverse and data assimilation problems. A new data assimilation algorithm for a three-dimensional transport and transformation model with unknown emission sources is presented, which uses an approach based on sensitivity operators and ensembles of solutions of adjoint equations implemented in the IMDAF inverse modeling system for distributed memory computers. When tested in a realistic Baikal region scenario, the algorithm enabled, based on the data of integrated vertical measurements simulating remote sensing data, reducing the error in the concentration field by 15%. With the given vertical level of the source location, the errors in the concentration field and in the source were reduced by 93% and 85%, respectively.

The isotopic composition of precipitation is a hydrological tracer of convective processes and is often used to reconstruct paleoclimate. Therefore, it is interesting to consider how the isotopic composition of precipitation changes during the passage of mesoscale convective systems (MCS). Variations in the isotopic composition of oxygen (δ¹⁸О) and hydrogen (δD) in precipitation during the passage of MCS over Tomsk in 2016-2021 were studied. It was found that δ¹⁸О values varied from -14.98 to +0.03‰ with an average of -9.9 ± 3.2‰ and δD values varied from -99.2 to -16.71‰ with an average of -65.1 ± 22.3‰ in MCS precipitation. The relationship between δ¹⁸О and δD is described by the equation δD = 5.45d¹⁸O - 11 ( R ² = 0.62). The values of the regression coefficients show the predominant effect of evaporative fractionation on the formation of the isotopic composition of precipitation. Relatively high isotope ratios corresponded to disorganized convection, and lower isotope ratios characterized the isotopic composition as the MCS area increased. Based on the analysis of back air mass trajectories with the use of the indices of convective instability and satellite sounding and WWLLN network data, regions-sources of moisture for MCS precipitation were detected: the underlying surface and shallow water bodies of the steppe zone in the south of Western Siberia and Northern Kazakhstan. The results of the study can be useful for simulating convection in climate models, as well as for better understanding isotope variations in different paleoarchives for regions with convective activity.

The information on the cloud liquid water path (LWP) is necessary for many applications including global and regional climate modelling, weather forecasting, and modelling of the hydrological cycle. The results of derivation of the land-sea LWP contrast from satellite measurements of LWP by the SEVIRI (Spinning Enhanced Visible Infra-Red Imager) instrument over land and water bodies in Northern Europe are presented. When studying the diurnal cycle of the LWP contrast for some water bodies, two separate maxima were discovered, which were observed nearly symmetrically relative to noon on the UTC time scale. In most cases, these maxima were present at measurement locations in the Gulf of Riga and in the Gulf of Finland in the Baltic Sea. Presumably, these maxima are an artefact of observations caused by the so-called “cloud bow effect”. Calculations of a scattering angle for the satellite measurements at these locations confirmed this conclusion. The problem of filtering out the data and the problem of analysing the data in case of possible manifestation of this confounding effect are discussed. The proposed approach to data analysis and the results can be used to assess the quality of LWP measurements by SEVIRI in various regions of the globe.

The climate of mountain regions is studied much worse than of plain territories. We suggest a model of the distribution of temperature field parameters in the lower troposphere over the Caucasus, which is to enable estimating the thermal resources of mountainous regions. Based on temperature sounding data at altitudes of 1500, 3000, and 5000 m from six aerological stations located on different sides in the mountainous country and regression and statistical analysis, we retrieve the temperature fields and distribution in the lower troposphere. The monthly average characteristics of the temperatures are presented; the effect of orography on the temperature regime is studied. The use of aeroclimatic temperature indicators makes it possible to indirectly estimate the thermal resources of mountain regions from analog station data for their effective use in economic activity.

The relationships between variations in the residual gas content in discs of coniferous and deciduous trees growing in and around Tomsk (southeastern Western Siberia) and the North Atlantic Oscillation (NAO) were analyzed. The results of the work showed that (1) air temperature in Tomsk region significantly correlated with the NAO index; (2) the cross-spectral analysis of the chronologies of gas components of the deciduous tree discs with the air temperature during the growing season indicated the coherent fluctuations around a 4-year cycle; (3) the correlation coefficients of the NAO index with the chronologies of CO₂ (CO₂ + H₂O), and the ring width of the six (of eight) tree discs were found. Based on the results, it is concluded that the North Atlantic Oscillation can affect the life activity of some Siberian tree species (on a 4-year time scale).

Modern changes in the global climate are accompanied by rising air and soil temperatures. How do they affect soil respiration and should we expect a change in greenhouse gas emissions? These questions cannot be answered without studying gas exchange between the soil and the atmosphere. In this paper, the analysis of the greenhouse gas fluxes at the soil-atmosphere interface observed at the Fonovaya Observatory in 2023 is presented. A stable CO₂ and CH₄ uptake throughout the growing season is shown. As for N₂O, on the contrary, a weak positive flux was observed. A steady uptake of carbon dioxide from the atmosphere occurred from May to mid-August; its value attained -600 mg × m^-2 × h^-1 in June and July. The methane flux (sink) attained -0.08 mg × m^-2 × h^-1. The nitrous oxide flux fluctuated near zero with the daily average being within ± 0.02 mg × m^-2 × h^-1. For CO₂, a nonlinear positive relationship between the increase in respiration of vegetation and soil temperature is revealed. Linear temperature dependences are found for methane fluxes in all three chambers, that is, an increase in soil temperature enhances CH₄ uptake. N₂O fluxes show very weak positive dependence on the soil temperature in both transparent chambers (with vegetation and without it). The estimates of the contribution of CO₂ fluxes from the soil showed that during nighttime, microbial respiration can contribute from 46.7 to 77.9% to the total respiration of the grassland ecosystem. On average, the share of soil methane uptake per day due to diffusion and oxidation by methanotrophs not associated with plants varies from 5.3 to 48.3%. The contribution becomes smaller during the daytime and increases at night. The contribution of soil with removed vegetation to the total N₂O emission can attain 92.3%. The results expand knowledge about soil-atmosphere gas exchange under changing climate conditions.

The volume concentration of fine and coarse aerosol ( V_f and V_с ) in the near-water layer and the aerosol optical depth (AOD) of the atmosphere are generalized on the basis of long-term studies in Eurasian sector of the Arctic ocean. The mean AOD value at 0.5 mm is 0.061, the Angstrom exponent is 0.9, the concentrations of fine and coarse aerosol are 0.35 and 2.5 μm³/cm³, respectively. The greatest content of fine aerosol is observed in the atmosphere over Norwegian and Barents Seas. The spatial distribution is characterized by the decrease in the concentrations in northern and eastern directions: the mean value V_f becomes 1.7 times less from Barents Sea to Chukchi Sea (from 0,43 to 0.26 μm³/cm³). The very high concentration of coarse aerosol are observed in south-east part of Kara Sea: the mean V_с is 4.18 μm³/cm³. Then the coarse aerosol concentration decreases relatively to Kara Sea in eastern and western directions by several times.

The influence of synoptic conditions at the 700 hPa isobaric surface on meteorological regime and melt of the Sygyktinsky glacier (Kodar Range) in the 2021 ablation season was studied. Totally 15 weather types were classified using the Jenkinson and Collison method. It was found that the most frequent types are cyclones (24%) and anticyclones (20%). A significant dependence of the meteorological regime of the glacier on synoptic conditions was revealed. Anticyclonic types are characterized by high temperatures and low relative humidity and cloudiness. For cyclonic types, the opposite relations are observed. It was found that the radiation regime on the glacier and its melting rate depend on synoptic conditions. The greatest contribution to melting was made by anticyclonic weather types (44%), and the least by cyclonic types (26%). The net radiation of the glacier in anticyclones was 2-2.5 times greater than in cyclones, and the ablation rate was 1.6-1.8 times greater. The differences between the energy fluxes used for glacier melting under different synoptic patterns are explained by the cloudiness. The different atmospheric circulation regimes over the Kodar significantly affected the deglaciation of the Kodar glaciers in recent decades.

The absence of an adequate optical model for cirrus clouds currently poses a significant challenge in interpreting ground-based and space-borne lidar data. This, in turn, leads to a lack of up-to-date information for climate modeling and daily weather forecasting. Existing optical models typically assume that ice crystals in cirrus clouds have an ideal shape, which is often not the case. This article proposes an optical model for clouds which consists of the most common irregularly shaped particles, specifically hollow hexagonal columns. The model takes into account the actual distributions of particles in the cloud over both depth of the cavity and particle size. Additionally, the model considers the scenario of a cloud containing a mixture of ideal hexagonal columns and hollow hexagonal columns, which significantly enhances the model reliability. The resulting model holds great practical importance for laser sounding of the atmosphere.

The substantiation of the design and technical description of the turbulent lidar BSE-6, intended for installation on board aircraft, is given. In order to reduce the overall dimensions of the system, both sides of the optical bench are used: a transceiver is installed on one side, and a receiving module is mounted on the other. The heat-generating elements are placed in separate insulated ventilated sections. To minimize the deformation of the optical bench, external air is pumped through its middle. The lidar adjustment procedure is described. The quality of the assembly and alignment was tested by comparing the theoretical calculation with real echo signals. The system was also tested for thermomechanical stability.

Ozone is a strong oxidizer, so monitoring the state of the ozonosphere is one of the most important tasks in ensuring the safety of human life and health. There are a number of methods for studying ozone, among which a special place is occupied by the lidar method of remote detection and identification using selective absorption of laser radiation due to its has maximal sensitivity. V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences solved the problem of monitoring the entire ozonosphere over Tomsk by combining existing lidar systems: three measuring systems of the Siberian Lidar Station and a mobile ozone lidar. Lidars are designed to study the ozonosphere using the method of differential absorption and scattering, as well as to study aerosol fields using single elastic scattering. The systems are based on SOLAR and LOTIS TII Nd:YAG lasers, a Lambda Physik laser, and receiving Cassegrain (0,35 m diameter) and Newton (0,5 m diameter) telescopes. Lidars operate in the photon counting mode and record lidar signals with a spatial resolution of 1.5 to 160 m at probing wavelengths of 299/341 nm in the altitude ranges ~ 0.1-12 km and ~ 5-20 km, and 308/353 nm in the altitude range ~ 15-45 km. By combining three measuring systems, a full-scale experiment of lidar sensing of the atmosphere in Tomsk was carried out. The result of retrieval of the vertical profile of ozone concentration is presented. For the first time in Russia, lidars have covered the entire ozonosphere. The lidar complex sounding results will be used in the network of Roshydromet stations, in adjusting the quasi-three-year model of the vertical distribution of ozone concentration and aerosol, in comparison of lidar and satellite data, and in assessing the influence of climate-forming factors in Western Siberia.

The study of the spatiotemporal structure of optical turbulence and the development of methods for determining its characteristics at different altitudes in the atmosphere are of great importance for astronomical adaptive optics. Design of an adaptive optics system and technical characteristics of its components largely depend on optical turbulence along the line of sight a telescope. In this paper, the method for estimation of vertical profiles of the air refractive index structure characteristic is modified. Based on the ERA5 reanalysis data, this method was used to derive statistically representative vertical profiles of the air refractive index structure characteristic and the outer scale of turbulence at the Large Solar Vacuum Telescope (LSVT) site. The problem of estimating the turbulence outer scale is discussed taking into account surface mast micrometeorological measurements and optical measurements at the LSVT. The results are the basis for constructing a multi-mirror adaptive optics system for the LSVT. In particular, these profiles are important for further refinement of the optical conjugation heights. The suggested method can also be used to describe optical turbulence over other ground-based solar telescopes.