Vol 23, No 4 (2023)
- Year: 2023
- Articles: 14
- URL: https://journals.rcsi.science/1681-1208/issue/view/15950
Articles
CONSISTENCY OF INTRA-CENTENNIAL OSCILLATIONS IN LENGTH OF DAY AND OCEANIC CHARACTERISTICS
Abstract
The paper presents analysis of intra-centennial (inter-decadal and multidecadal) variations of the length of day (LOD) and some oceanic parameters such as sea surface temperature (SST) and sea level (SL). Methods of multivariate regression analysis and correlation analysis are used. Results of the regression analysis show a spatially coherent response of SST to LOD variations on the multidecadal time scale. The earlier response is peculiar to the north and tropical Atlantic where the multidecadal SST variations are approximately opposite to the LOD variations. In the most remaining parts of the oceans, except especially in the Nino 3.4 region of the equatorial east Pacific, the multidecadal SST variations are generally lagged relative to the antiphase variations of the LOD. Smoothing of SST averaged over different areas and of the global mean SL shows that the intra-annual variations include inter-decadal, 20–30-year, multidecadal, 60–70-year, components that correspond to similar oscillation components in the LOD. The most striking correspondence of the two components is observed between the LOD and SST averaged over the Nino 3.4 region. Generally, there are significant correlations of the intra-centennial variations on the averaged and smoothed SST series and global mean SL with the LOD variations. We propose that angular momentum exchange processes involving oceanic circulation and interactions between the Earth’s core and the mantle play probably a part in the observed relationships of intra-centennial variations in oceanic parameters with variations in the LOD.
ACCUMULATION CHARACTERISTICS OF BRYOPHYTES IN ABANDONED DISTURBED PEATLANDS: A CASE STUDY FROM THE KALININGRAD REGION, RUSSIA
Abstract
NUMERICAL SOLUTION OF A TWO-DIMENSIONAL PROBLEM OF DETERMINING THE PROPAGATION VELOCITY OF SEISMIC WAVES IN INHOMOGENEOUS MEDIUM OF MEMORY TYPE
Abstract
LINEAR PERTURBATIONS OF THE BLOCH TYPE OF SPACE-PERIODIC MAGNETOHYDRODYNAMIC STEADY STATES. II. NUMERICAL RESULTS
Abstract
We consider Bloch eigenmodes of three linear stability problems: the kinematic dynamo problem, the hydrodynamic and MHD stability problem for steady space-periodic flows and MHD states comprised of randomly generated Fourier coefficients and having energy spectra of three types: exponentially decaying, Kolmogorov with a cut off, or involving a small number of harmonics (“big eddies”). A Bloch mode is a product of a field of the same periodicity as the perturbed state and a planar harmonic wave, exp(iq · x). Such a mode is characterized by the ratio of spatial scales which, for simplicity, we identify with the length |q| < 1 of the Bloch wave vector q. Computations have revealed that the Bloch modes, whose growth rates are maximum over q, feature the scale ratio that decreases on increasing the nondimensionalized molecular diffusivity and/or viscosity from 0.03 to 0.3, and the scale separation is high (i.e., |q| is small) only for large molecular diffusivities. Largely this conclusion holds for all the three stability problems and all the three energy spectra types under consideration. Thus, in a natural MHD system not affected by strong diffusion, a given scale range gives rise to perturbations involving only moderately larger spatial scales (i.e., |q| only moderately small), and the MHD evolution consists of a cascade of processes, each generating a slightly larger spatial scale; flows or magnetic fields characterized by a high scale separation are not produced. This cascade is unlikely to be amenable to a linear description. Consequently, our results question the allegedly high role of the α-effect and eddy diffusivity that are based on spatial scale separation, as the primary instability or magnetic field generating mechanisms in astrophysical applications. The Braginskii magnetic α-effect in a weakly non-axisymmetric flow, often used for explanation of the solar and geodynamo, is advantageous not being upset by a similar deficiency.
ASYMPTOTICS OF FAR FIELDS OF SURFACE AND INTERNAL GRAVITATIONAL WAVES FROM LOCAL AND NONLOCAL PERTURBATION SOURCES
Abstract
SPREADING OF THE AMAZON RIVER PLUME
Abstract
Results of a joint Russian-Brazilian expedition to study the dynamics of continental river runoff in the ocean associated with the Amazon plume are presented. The stations of the study region covered the seaward part of the Amazon plume. The work was carried out in the dry season (November). The data of in situ measurements and satellite data show that the most desalinated and rich in suspended particulate matter and chlorophyll-a waters were localized on the shallow inner shelf. The horizontal and vertical structure of the thermohaline fields indicates the presence of a well-pronounced river plume about 15 m thick. The decrease in salinity in the plume relative to the background values exceeded 6 PSU even at 300–400 km from the river mouth. The plume waters were characterized by increased concentrations of suspended matter. The best approximation to the in situ measurements is provided by the SMOS satellite salinity data and reanalysis GLORYS12. Chemical determinations in the surface layer in the area of the plume reveal elevated concentrations of silicates, phosphates, and nitrites compared to the seaward part.
MODELING OF STRONG GROUND MOTION WITHIN THE BAIKAL RIFT ZONE: THE IRKUTSK CASE
Abstract
The Baikal Rift Zone is seismically active and each well recorded strong earthquake (for example, as the Kultukskoe earthquake (South of Baikal), on August 27, 2008, with Mw = 6.3) is the reason to refine existing models for seismic hazard estimates. There are several approaches to study strong ground motion, and one of them is to model synthetic accelerograms to reconstruct the rupture process. In this paper we are mostly interested in calculating accelerograms for the city of Irkutsk, considering source spectra with two corner frequencies, primarily, to reconstruct impact from the Kultukskoe earthquake.
COMPARATIVE ANALYSIS OF THE UNMANNED AERIAL VEHICLES AND TERRESTRIAL LASER SCANNING APPLICATION FOR COASTAL ZONE MONITORING
Abstract
The shallow sandy shores of the tideless sea are regularly affected by storm activity. Foredune ridge is a natural and anthropogenic object, a natural protective barrier that protects ecosystems and populated areas from the effects of dangerous hydrometeorological phenomena such as storm surges and wind-sand flux. In the course of impact of dangerous hydrometeorological phenomena, the foredune ridge integrity is disturbed, the composing material is washed away thus forming breakthroughs. Monitoring of the foredune state is an important stage in maintaining its condition and also provides an empirical basis for predicting the impact of hazardous events. The use of ground-based laser scanning technology as well as digital photogrammetry for the study of sensitive coastal zones is justified for these purposes. In this article, we compare the results of calculating the dynamics of the beach sand material and advance them according to the results of ground-based laser scanning and digital photogrammetry. Comparability is provided by high-density clouds of ground-scan points and digital photogrammetry in a single coordinate reference. Two sections of the sensitive coastal zone of the Curonian Spit (Russian sector of the South-Eastern Baltic) have been explored in advance. A comparison of the applicability of means for obtaining digital elevation models to evaluate the dynamics of sand material has been made. In comparison with TLS, the use of UAV with the SfM algorithm is limited to post-storm surveys, since the final accuracy does not provide for reliable lithodynamic studies due to the small scale of processes comparable to measurement errors.
CONGRATULATIONS ON THE 75TH ANNIVERSARY OF ALEXEI GVISHIANI
Abstract
SOLID RUNOFF OF THE DON RIVER AND SUSPENDED MATTER FLOW INTO THE DELTA DURING SURGES: STATISTICAL MODELING AND COMPARISON IN THE LOW WATER PERIOD
Abstract
GEOELECTRIC MONITORING OF EARTHEN HYDRAULIC STRUCTURE STATE BY RESISTIVITY AND INDUCED POLARIZATION METHODS: MINE WATER SETTLING POND DAM CASE STUDY
Abstract
In earth dams, a permanent filtration of water leads to washing out of sand-clay fraction and to a formation of soil decompression sites, which pose a danger to embankment integrity. Condition monitoring of earth hydraulic structures can be executed by geophysical methods. The article presents the results of geoelectric monitoring conducted on the dam of settling pond of mine water with high metal content. The investigations were carried out by vertical electrical soundings, including electrotomography, and by methods of induced polarization in time and frequency domains. According to the results of the electrical soundings, places of reduced soil resistivity in the dam were identified, associated with infiltration of precipitations and of water from the pond. Geoelectric monitoring showed changes of the soils resistivity in different years, depending on hydrological conditions. Induced polarization methods are sensitive to material composition of soils, such as clayiness and presence of electronically conductive minerals. It is determined that the highest content of clay is in the upper and middle parts of the embankment. In eastern part of the dam, intensive polarizability of the medium was detected. It can be caused by filtration of water, contaminated with metals, through the embankment and sedimentary rocks. Thus, by resistivity measurements, it is possible to identify areas of intensive filtration in the dam body, and induced polarization measurements make it possible to determine clay content in the soil and possible pathways of contamination through the dam, which is of great importance for studying the environmental situation of region.
STUDIES OF THE ELECTRICAL RESISTIVITY TOMOGRAPHY MONITORING OF THE ISSYK-ATA FAULT ZONE (NORTHERN TIEN SHAN)
Abstract
EVALUATION OF DISPLACEMENTS CAUSED BY STRIKE-SLIP DEFORMATIONS USING CORRELATION CHARACTERISTICS BASED ON POTENTIAL FIELD DATA
Abstract
The identification of faults is a common objective in geophysical potential field methods. Vertical discontinuities such as reverse faults, also known as tectonic faults, can easily be distinguished through their effect on gravity and magnetic fields, appearing as gradient zones or areas of change in the field. However, identifying strike-slip faults is one of the biggest challenges for potential field methods as they are characterized by a complex series of anomalies with varying signs in the fault zone, as well as displacement of anomaly axes between the strike-slipped blocks. The goal of this study is to suggest a transformation that would aid in the identification of shear zones through the calculation of the displacement along the discontinuity. The proposed approach involves calculating the correlation coefficient between parallel profiles using moving windows. The position of the window with the highest calculated correlation coefficient allows estimating of the discontinuity displacement magnitude. The method was tested using a synthetic field and data from the magnetic field of the Kolbeinsi Ridge.