The architecture was developed, and a digital platform for continuous monitoring of high-precision GPS measurements of two observation points ULAZ (Ulan-Ude) and BADG (Badary) was created. The sounding of the atmosphere with signals of the Global Navigation Satellite System (GNSS-GPS) makes it possible to continuously obtain the values of zenith total tropospheric delay (ZTD) and integrated water vapor (IWV) content of the lower atmosphere. Currently, primary GPS data for both observation sites, processed ZTD data processed data on the IWV content of the lower part of atmosphere are accumulated.
To determine the level of integrated water vapor (IWV) within the lower neutral part of the atmosphere, data from the Global Navigation Satellite System (GNSS or GPS) are used. Radiosonde (RS) data are essential for the direct detection of IWV content and for finding the weighted “mean temperature” (Tm) in the conventional vertical column, it plays a significant role in extracting values of IWV from the GPS data set. For observation points Yakutsk and Tiksi, linear and quadratic models of Tm are given. To determine the accuracy of the level of moisture content over the city of Yakutsk according to GPS observations, taking into account the quadratic model, a comparison was made with the data on RS and the reanalysis data of ERA5.
The levels of integrated water vapor (IWV) within the lower part of the atmosphere are obtained from the data of the global satellite navigation system (GPS) and radiosondes (RS). Long-term trends in the total moisture content of the troposphere were obtained at the observation points IRKM (Irkutsk) and YAKT (Yakutsk). Comparison of the trends with calculations by the Hopfield model, which takes into account surface weather data, showed a better agreement between GPS measurements than RS. There is an upward trend in IWV according to GPS observations over the entire period of the study, and, despite the large latitudinal differences in the observation points, there is a positive general trend of 0.31±0.02 mm per decade.
An experimental wind wave monitoring station has been set up on the eastern coast of Middle Baikal. Tests were carried out by direct measurements using a video recorder installed on a measuring pole near the coastline. The characteristics of the wind were measured synchronously with an anemometer. In the conditions of open Baikal in shallow water in the daytime, the dependence of the height of the waves on the speed and direction of the wind has been established. In the morning, with an increase in the wind speed of the southwestern direction, the generation of wind waves begins. The maximum height of the waves in the second half of the day with the western wind direction is established. The measurements were taken in autumn.
The time series of troposphere moisture content levels obtained at the ULAZ point (Ulan-Ude, N51°48′, E107°37′, h=517 m) were compared according to GPS observations and surface meteorological observations during 2011 - 2020. The calculation of the total zenith tropospheric delay (ZTD) from surface weather data was performed using a simplified formula for mid-latitudes, when the troposphere height for water vapor was limited to 11 km. The linear trend of the total moisture content PW at the ULAZ according to GPS observations was +0.91 mm per decade and +0.82 mm per decade according to surface weather data. Although a 10-year period may not accurately reflect real climate trends, it is nevertheless possible to make an estimate of a marked positive change.
The values of the integrated moisture content from GPS measurements and a microwave water vapor radiometer (WVR) are compared. Measurements are regularly carried out at the permanent observation point BADG located at the Badary Observatory (Institute of Applied Astronomy of Russian Academy of Sciences). GPS antenna, WVR device and weather station are located in close proximity to each other. This significantly affected the accuracy of the processed data. Differences in the values of the integrated moisture content obtained from GPS observations and measurements with a microwave water vapor radiometer are analyzed in terms of mean and standard deviations, as well as the cross-correlation coefficient. In summer, the average deviation of the difference in the level of moisture content in the troposphere according to GPS and WVR observations was about 0.63% of the average summer value. In winter, the average deviation of the difference was about 0.21% of the average winter value. A high degree of reliability of data on the moisture content of the troposphere obtained by the method of permanent GPS measurements is shown.
In March 2021, a ground-penetrating radar survey was conducted of the only official ice crossing over the Selenga River in the Mostovaya microdistrict of the Zheleznodorozhny district of Ulan-Ude city. GPR "Oko-2" with antenna blocks AB-1700 (center frequency 1700 MHz) and AB-400 (center frequency 400 MHz) was used for sounding. The thickness of the ice on the ice crossing is 0.5-1.2 m and exceeds the thickness of the ice outside the crossing by 0.1 – 0.2 m. The presence of snow cover outside the crossing limits the freezing of the ice layer. Calibration sounding of the ice with drilling of the well gave the ice permittivity ε = 3.17. The electrical resistivity of the water from the well is 74 Ohm·m at the temperature of 1°C.
A model for the propagation of LF-MF radio waves over ice paths with a spatial change in impedance is proposed and substantiated by numerical calculations. Its features are determined for a two-layer “ice-sea” radio path with a spatial change in ice thickness. The surface impedance, the attenuation function W and the field level |Ez| over a two-layer ice path are considered with a spatial change in ice thickness at a frequency of 300 kHz according to: a) harmonic law and b) sawtooth change in ice thickness. The simulation results are necessary to estimate the conditions for the propagation of LF-MF-HF radio waves along the paths of the Northern Sea Route.
The results of modeling the conditions of propagation of LF-MF radio waves over the impedance structure "thick ice - sea" in the Arctic Ocean are presented. To calculate the electromagnetic field of the two-layer structure “thick ice-sea”, the applicability regions of impedance boundary conditions for a vertically polarized wave depending on the thickness of the ice are determined. Methods of calculating the ground wave field tension on high-latitude impedance paths with an ice thickness of 2-9 meters are considered. The results are necessary for calculating the attenuation function W and the field level E of radio waves.
In the lower atmosphere, the deviation of the trajectory of radio waves occurs due to the variability of the refraction of air with height. The vertical profile of the refractive index substantially depends on the geographical position, altitude and time of year of observation. The refractive properties of the troposphere and tropospheric delays of signals in different seasons of the year are considered at polar points of observation Murmansk, Wiese Island, Norilsk, Tiksi and Yakutsk. Altitude meteorological data is determined by launching radiosondes or selected on the NOAA remote sensing site. Knowing the vertical gradient of the refractive index is the basis for calculating the angles of refraction and the true distance to the object, which can be located above the level of the troposphere. The possibility of using the GPS measurement method to study the refractive effects of the troposphere without taking into account meteorological data is shown.
The field of the ground wave which is created by a vertical electric dipole above an inhomogeneous surface of the Earth is considered. For inhomogeneous radio paths, the calculation of the attenuation function of the ground wave field is proposed to be performed by the method of the Feinberg’s integral equation, which takes into account the underlying medium in the form of a multi-sectional impedance path. This method allows performing calculations in the LF-MF ranges of radio waves over long paths with relatively "poor" conductivity of the medium. In the initial homogeneous section of the radio path, the attenuation function is calculated according to the model of a “flat” Earth surface using Sommerfeld's formulas. The values of the attenuation function of the ground wave field over permafrost radio paths in the North-East of Russia are calculated.
The results of the study of the Barguzinsky Bay geoelectric profile on Lake Baikal according to GPR and radioimpedance soundings are presented. The technique of the bottom electric mapping of the coastal zone of the Barguzinsky Bay water area on Lake Baikal by resistivity within the framework of a multilayer medium model with a poorly and well conducting base is proposed. A comprehensive interpretation of radioimpedance and GPR soundings made it possible to obtain detailed information on the geoelectric structure of the aquatic environment of the Barguzinsky Bay on Lake Baikal.
For calculations of the electromagnetic field of the two-layer "thin ice-sea" structure, the areas of applicability of the impedance boundary conditions are determined depending on the thickness of the ice and the angle of incidence of the vertically polarized wave. Results are needed to calculate the attenuation function W and the radio wave field level. It is shown that for the "thin ice-sea" structure, taking into account the dependence of surface impedance on the angle of incidence is important for over-the-horizon radar systems in the HF range of radio waves. In the VHF range for ice 80 cm thick, frequency bands are identified in which impedance boundary conditions are applicable.
Propagation conditions of radio waves over the “ice-sea” structure with a highly inductive impedance are often more favorable than over a clear sea due to the appearance of a surface electromagnetic wave. Numerical calculation algorithms for various radio wave propagation path models have been developed. The method of making prognostic maps of the surface impedance of the “ice-sea” structure according to the ice situation maps for the Arctic Ocean (AO) in different seasons of the year is considered. A formula is proposed for converting the spatial dependence of the ice thickness into the spatial dependence of the surface impedance at a fixed frequency in VLF-LF-MF ranges. Calculations of surface impedance for various types of sea ice are presented.
KEYWORDS: General packet radio service, Global Positioning System, Soil science, Radar, Satellite navigation systems, Meteorology, Data modeling, Signal attenuation, Atmospheric sciences, Materials science
In connection with the growing interest in the development of the coast and the shelf of the Arctic Ocean, it seems relevant to study the frozen section of the Arctic coast by radio wave methods. The results of studying the geoelectric section of frozen soils and rocks of the Arctic coast in the vicinity of Tiksi by means of radio impedance and GPR sounding are presented. An experience of studying the frozen soils and rocks of northern Yakutia by means of a complex of radio physical methods of introscopy (radio wave diagnostics) of the underlying layered inhomogeneous medium (VLF-LF radio-impedance sounding and GPR) was summarized. The area of researches refers to the zone of permafrost. Series of long-term observations of total zenith tropospheric delay (ZTD) and its "wet" component (ZWD) for the permanent observation point TIXI are considered. A comparative analysis of direct measurements of the depth of thawing of cryolithozone soils, the results of ground-based radio wave soundings and GPS measurements has shown that it is possible in principle to determine the depth of thawing of cryolithozone soils using radio signals from the global navigation satellite system (GNSS).
The possibility of using passive satellite sounding of the atmosphere in order to obtain data of vertical pressure distribution, temperature and relative humidity for modeling the altitude dependence of the refractive index of air is considered. Seasonal parameters of the exponential model of tropospheric refraction over the permanent points of GPS observations of the Baikal region (Irkutsk (IRKM), Ulan-Ude (ULAZ) and Badary, Tunka valley (BADG)) are obtained. Comparative calculations of the angles of refraction in different seasons of 2017 are performed. Calculations showed an insignificant difference in the refraction angles at the points of observation of the Baikal zone in order of magnitude from other climatic zones. In addition to high-precision geodesy, the GPS global positioning method can continuously determine the total zenith tropospheric delay (ZTD) which is related to the geometric parameters of refraction and has applications in radio physics and meteorology.
The lower neutral part of the atmosphere (troposphere) where the GNSS signals are refracted is one of the reasons for the errors in the accuracy of GPS positioning. The total zenith tropospheric delay (ZTD) is the difference between the assumed straight line along which the GPS signal propagates at the speed of light in a vacuum and the actual path from source to receiver. Atmospheric water vapor affects the speed of propagation of GPS signals, and it is characterized by rapid variability as well as a significant mutual influence on the variability of other meteorological parameters. The possibility of determining the content of water vapor in a conventional vertical column to the level of the upper part of the troposphere using the GPS measurement method, as well as using meteorological data is considered. The results of processing primary GPS data give continuous atmospheric data in the form of a total zenith tropospheric delay (ZTD). Data on the “wet” component of the total zenith tropospheric delay (ZWD) can be converted with very high reliability into the integrated water vapor (IWV) data above the observation point.
The altitude dependence of the electromagnetic field above the arctic path at a frequency of 300 kHz (GLONASS CCS) is considered. When comparing the altitude dependences of the modulus of the attenuation function |W| and field level E for the radio paths "ice-sea" and "sea" it is shown that the conditions for propagation of radio waves over ice-covered sea at reception altitudes up to 3-10 km are more favorable than over the open sea. It is established that the propagation over the ice paths depends on the height of the reception. The field of a vertical electric antenna over an “ice-sea” structure with highly inductive impedance exceeds the field of the earth's wave above the open sea. It decreases with increasing reception height. This effect is due to the concentration of the field above the highly inductive medium interface. Insignificant growth of the field above the sea occurs with an increase of the reception height.
The report is devoted to the foundation of the method of calculation of the service zone of the MF radio beacon for transmission of differential corrections of the global navigation satellite system (GNSS) over high-latitude manysectional impedance paths in summer and winter time. Methods of calculation of the Earth’s wave field over inhomogeneous radio paths including over layered “ice-sea” structure are considered. On a base of the analysis of propagation conditions of radio waves, a new method of calculation of the service zone of the radio lines in the Arctic basin was submitted. Numerical algorithms for various models of the propagation of radio waves were developed and tested. The method consists in using the proposed set of algorithms, maps of geoelectric sections (GES) of underlying layered medium, digital relief maps, vegetation and ice cover for the calculations of Earth’s wave fields.
Results of the modeling of the propagation of LF-MF radio waves over radio path with variable surface impedance were considered. Formulas to convert the spatial dependence of ice thickness in the spatial dependence of the surface impedance at a fixed frequency of LF-MF ranges were offered. The calculation of the field magnitude was carried out using the program of calculation of field of an attenuation function W by the method of the Hufford’s integral equation. Results of calculations of surface impedance, an attenuation function and field magnitude on a frequency of 518 kHz on a 400 kilometers section of the radio path “Tiksi - North pole”.
Predictive map of geoelectric sections of the North China on a scale of 1 : 2 500 000, necessary for calculation of propagation of VLF-MF radiowaves, is constructed. Taking into account the layered structure of the underlying medium, this map is capable of increasing the accuracy of electromagnetic field calculations by 1.5-3 times as compared to the Morgan-Maxwell map. The methodology of the geoelectric mapping is described. The studies of electrical properties of layered media by combined radio and geophysical methods in a variety of natural and geological conditions, and the proposed method of geoelectric mapping have resulted in the construction of a new generation of maps showing the electrical properties of the underlying medium that account for the layered structure of the crust and have no analogues in the world.
The paper is devoted to estimation of the LF-MF high latitude communication radio lines range on surface electromagnetic waves (SEW). A surface impedance of sea areas of water in summer and winter time is considered. An example of calculations of the ground wave field over inhomogeneous impedance paths including stratified inhomogeneous structure “ice-sea” is given. It is shown that due to the emergence of SEW the Arctic radio lines range increases significantly.
Results of modelling the fractal by geometry of a skin-layer HS and the module of a surface impedance |δ| of a
geoelectric cut of item of measurement "Lake" are considered. Frequency dependences of a skin-layer HS and the
module of a surface impedance |δ| become sedate: HS ~ f-D, and |δ| ~ f1-D, where f- frequency. In a range of
1 Hz - 1 MHz the following is received: HS ~ f-0.48, and |δ| ~ f0.53. Results mean, that spending sites of
considered item of measurement form Cantor set with dimension the fractal D = 0.47 ± 0.01.
Results of geoelectric mapping of the some countries of Asia with high seismic activity are presented. The methodology
of the geoelectric mapping is considered. Maps of geoelectric sections of Turkey, Iran, Afghanistan, Pakistan, Korea, and
Japan on a scale of 1:5 000 000 are constructed. The scale of ρj and hj has three gradations per decade.
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