Institute of Monitoring of Climatic and Ecological Systems

One approach to constructing terahertz radiation sources for analyzing atmospheric gas composition is based on the use of nonlinear optical generators that convert the frequencies of intense near-infrared laser sources. This method’s downside is that its efficiency is proportional to the square of the generated frequency. This paper proposes a solution based on the use of cascade conversion, which involves generating intermediate frequencies in a local infrared transparency window of a nonlinear crystal and then downconverting these frequencies to the subterahertz region. For the first stage, an enhanced conversion due to a significant increase in quadratic susceptibility near optical phonons or stimulated polariton scattering is allowed. A second-stage model is considered for the process of subterahertz difference frequency generation under pumping in the local infrared transparency window in a KTP crystal. The fulfillment of collinear phase matching is demonstrated, and the figure of merit is estimated.

The article discusses the possibility of using the acoustic-electrical transformation method to detect cracks and mechanical compressive strength of concrete. Numerical and experimental studies of changes in the parameters of the electromagnetic response of model samples of concrete made of a cement-sand mixture with a crack to a deterministic pulsed acoustic impact are presented. It is shown that the presence of a crack is determined by changes in the amplitude-frequency parameters of the electromagnetic response from the sample. An example of determining the locations of weakening of the mechanical strength of a concrete construction beam based on the parameters of electromagnetic signals is given. The results of comparative tests for determining the mechanical compressive strength of concrete, obtained using a calibrated sclerometer and an acoustic-electric method, are shown. The results of monitoring the mechanical strength of concrete structures of an operating bridge crossing over a river are also presented based on the parameters of the electromagnetic response that arise during impact probing with acoustic pulses.

Two methods for stratospheric polar vortex delineation are compared by the main vortex characteristics they provide: vortex area, average wind speed at the edge, mean temperature inside the vortex. One of the methods is based on the geopotential, and another one is based on the potential vorticity (PV). Both methods use ERA5 reanalysis data on isobaric and isentropic surfaces. The geopotential method yields 1.3‑time higher vortex area for the Arctic and 1.14-time higher for Antarctica than the PV method. The estimates of the average wind speed at the vortex edge are very close: the wind speed by PV method is 5% higher than by the geopotential method for the Arctic and 3% higher in Antarctic. Mean temperature inside the vortex by PV method is 1% lower in both the Arctic and Antarctica. The maximal differences in the estimates of the vortex area are 25.52 million km2 in the Arctic (on November 23, 2022, on the 600-K isentropic surface) and 23.78 million km2 in Antarctica (on December 14, 2022, on the 475-K surface). These differences increase with the altitude: from 4.23 million km2 on the 475-K surface to 10.24 million km2 on the 600-K surface in the Arctic, and from 4.91 million km2 on the 475-K surface to 6.17 million km2 on the 600-K surface in Antarctica. The significant difference in the vortex area confirms a need in careful selection of the delineation method when studying polar vortices.

Aim: The paper presents the results of the study of the dynamics of methane and carbon dioxide fluxes for the ridge-hollow oligotrophic bog complex in the middle taiga subzone of Western Siberia. Correlations between carbon dioxide and methane fluxes were revealed and the influence of meteorological parameters on greenhouse gas fluxes was estimated. Methods: Greenhouse gas fluxes were measured using the KASM8 chamber automatic monitoring system with eight transparent chambers and LI-COR LI-7810 gas analyser to analyze CO₂, CH₄ and H₂O concentrations. Results: The mean values of CO2 and CH4 fluxes for the study period were obtained; differences in the functioning of the ridge and the hollow are shown: median values of CO2 fluxes indicate a greater uptake on the ridge (-74.4 mgCO2/m2/h) than on the hollow (-52.7 mgCO2/m2/h); methane fluxes on the ridge (0.08 mgCH4/m2/h) are on average 20 times lower than on the hollow (2.76 mgCH4/m2/h). Correlation of greenhouse gas fluxes with environmental factors were revealed: the highest correlations were found with the intensity of incoming solar (r = -0.84 ÷ -0.91) and photosynthetically active radiation (r = -0.85 ÷ -0.92), air temperature (r = -0.51 ÷ -0.63) and relative air humidity (r = +0.56 ÷ +0.62) and wind speed (r = +0.39 ÷ +0.50). Conclusions: Correlations between specific greenhouse gas fluxes were estimated based on spatial and temporal flux variability data. Correlations between greenhouse gas fluxes are different at night and daytime, which is directly related to external factors and principles of ecosystem functioning.

Abstract This paper presents the INM RAS–MSU land surface scheme, extracted from the INM RAS Earth system model into an independent software complex and supplemented with several modules to reproduce new components and processes of the Earth system. The resulting software product is referred to as TerM (Terrestrial Model). The physical and mathematical foundations of the model, the main features of the software implementation, and examples of applications in reproducing components of the terrestrial hydrological and carbon cycles are briefly outlined. Separating the land surface block into a standalone software complex significantly saves computational resources when assessing the impact of global and regional climate changes on natural resources (including hydrological ones), ecosystem dynamics, and emissions of climate-relevant substances with high spatial detalization. Within the TerM modelling complex, the development, validation, and calibration of new parameterizations of physical and biogeochemical processes are being conducted in an autonomous mode for subsequent implementation into the full INM RAS Earth system model.

The dynamic barrier is one of the physical characteristics of the polar vortices; it prevents subpolar air masses from penetrating into the vortex and contributes to a temperature decrease inside the vortex in the lower stratosphere. In the presence of a dynamic barrier in winter, chlorine compounds involved in the ozone destruction cycle accumulate on particles of polar stratospheric clouds (PSCs) and heterogeneous reactions occur with the formation of molecular chlorine, and with the appearance of solar radiation over the polar region, photochemical reactions begin, leading to large-scale ozone depletion. When the dynamic barrier is weakened in winter, the temperature inside the vortex rises, PSC melts and, thus, the accumulation of chlorine cycle reagents on PSC is interrupted. We proposed dividing the Arctic polar vortex dynamics into 3 types according to the consequences: (1) the strong vortex, whose activity results in ozone depletion, (2) the weak vortex with breakdown in winter, marked by a sudden stratospheric warming, and (3) the stable vortex with an episode (episodes) weakening of the dynamic barrier in winter without ozone depletion in the period from late winter to spring. We have for the first time proposed a characteristic of the dynamic barrier of the polar vortex at all pressure levels from 100 to 1 hPa and described the consequences of its weakening. Using the vortex delineation method based on the data of the ERA5 and MERRA-2 reanalyses, we showed that in all cases when the polar ozone depletion was not recorded from late winter to spring under the conditions of the stable polar vortex, the dynamic barrier weakening and PSС melting was observed in midwinter.

Changes in the spectral characteristics of the vibrational bands of n-butane have been studied in the spectral range 300–1100 cm–1 at a temperature varied from 285 to 365 K and a methane pressure varied in the range 2–40 atm. It was established that the enthalpy of the trans–gauche transition of n-butane in the gas phase is 657 ± 66 cal/mol. The methane pressure in the given range was found to have a negligible effect on the conformational equilibrium of n-butane. The impact of changes in the spectral characteristics of n‑butane on the accuracy of measuring the composition of natural gas using Raman spectroscopy was determined.

The dynamic characteristics of the stratospheric polar vortices at the levels from 100 to 1 hPa (minimum vortex area, minimum mean wind speed along the vortex edge, and the minimum wind speed at which there is a dynamic barrier is maintained) are presented for the first time. These parameters were obtained with the use of the vortex delineation method with the geopotential on the basis of the ERA5 reanalysis data. Seasonal changes and the average winter vertical profiles of the vortex area, mean wind speed along the vortex edge, and mean temperature inside the vortex for the Antarctic and Arctic polar vortices were obtained. The average daily probability of the dynamic barrier weakening along the vortex edge in winter was determined on the basis of data for 1979–2021 over the Arctic and Antarctic. It was shown that the lowest probability of the dynamic barrier weakening (and possible breakdown of the polar vortex) in winter can be traced at levels from 30 to 3 hPa and reaches less than 50% in the Arctic and less than 1% in the Antarctic. At the level of 50 hPa, the probability of the dynamic barrier weakening is 53.7% in the Arctic and 1.4% in the Antarctic.