Otto Chkhetiani - Academia.edu (original) (raw)

Papers by Otto Chkhetiani

Research paper thumbnail of Four-thirds law of energy and magnetic helicity in electron and Hall magnetohydrodynamic fluids

Physica D: Nonlinear Phenomena

Research paper thumbnail of Influence of nonlinear interactions on the development of instability in hydrodynamic wave systems

Journal of Experimental and Theoretical Physics, 2016

The problem of the development of shear instability in a three-layer medium simulating the flow o... more The problem of the development of shear instability in a three-layer medium simulating the flow of a stratified incompressible fluid is considered. The hydrodynamic equations are solved by expanding the Hamiltonian in a small parameter. The equations for three interacting waves, one of which is unstable, have been derived and solved numerically. The three-wave interaction is shown to stabilize the instability. Various regimes of the system's dynamics, including the stochastic ones dependent on one of the invariants in the problem, can arise in this case. It is pointed out that the instability development scenario considered differs from the previously considered scenario of a different type, where the three-wave interaction does not stabilize the instability. The interaction of wave packets is considered briefly.

Research paper thumbnail of Jumber Lominadze (In Honor of His 70th Birthday)

Plasma Physics Reports, 2001

Research paper thumbnail of CALIOP-Based Evaluation of Dust Emissions and Long-Range Transport of the Dust from the Aral−Caspian Arid Region by 3D-Source Potential Impact (3D-SPI) Method

Remote Sensing

The average monthly profiles of the dust extinction coefficient (ε) were analyzed according to th... more The average monthly profiles of the dust extinction coefficient (ε) were analyzed according to the CALIOP lidar data from 2006–2021 for 24 cells (size of 2° × 5°) in the Aral-Caspian arid region (ACAR; 38–48°N, 50–70°E). Using the NOAA HYSPLIT_4 trajectory model and the NCEP GDAS1 gridded (resolution of 1° × 1°) archive of meteorological data, the array of >1 million 10-day forward trajectories (FTs) of air particles that started from the centers of the ACAR cells was calculated. On the basis of the FT array, the average seasonal heights of the mixed layer (ML) for the ACAR cells were reconstructed. Estimates of the average seasonal dust optical depth (DOD) were obtained for ACAR’s lower troposphere, for ACAR’s ML (“dust emission layer” (EL)), and for the lower troposphere above the ML (“dust transit layer” (TL)) above each of the ACAR cells. Using the example of ACAR, it is shown that the analysis of DOD for the EL, TL and the surface layer (SL; the first 200 m AGL) makes it pos...

Research paper thumbnail of The Relationship between a Surface Electric Field and an Arid Aerosol under Different Wind Conditions

Doklady Earth Sciences

Abstract The relationship between the concentration of an arid aerosol 0.2–0.4 microns in size an... more Abstract The relationship between the concentration of an arid aerosol 0.2–0.4 microns in size and the electric field strength is investigated using field measurements carried out on a desert territory in Kalmykia in 2020. It is shown that the increase and decrease in the electric field strength is associated with a change in the wind velocity and the its direction relating to the dune ridges. An increase in the electric field strength occurs at wind velocity close to the threshold value and when the wind direction is close to the tangent to the crest line of the dune. According to an analytical estimate, the relative change in the electric field strength is proportional to the square of the number of microparticles generated. Free microparticles, pushed up by the electric field from the saltation layer, appear at the moment of accumulation of a critical charge on the saltation particle. Particle charging occurs faster with small bounces of particles, as in the tangential direction or when the wind velocity is close to the threshold. The influence of aeolian ripples on the motion and the height of the jumps of the saltating particles is noted at wind directions of 25°–45° to the crest line, as a weakening of the electric field with an increase in the number of microparticles.

Research paper thumbnail of Turbulent field helicity fluctuations and mean helicity appearance

International Journal of Non-Linear Mechanics, 2012

There are many experiments where nonzero mean turbulent helicity is measured either directly or i... more There are many experiments where nonzero mean turbulent helicity is measured either directly or indirectly. Despite the study of mechanisms of its occurrence, the question of mean helicity generation remains open. In our paper, we explore the emergence of the mean helicity in the turbulent field created by an external random force with zero helicity under a simultaneous external large-scale impact (rotation or homogeneous magnetic field). It is shown that anisotropy (even weak one) results in the appearance of mean helicity and in the emergence of an analog of the diamagnetic effect in the vortex field.

Research paper thumbnail of Planetary Upper-level Frontal Zone in the Euro-Atlantic Sector in Summer in 1990–2019

Russian Meteorology and Hydrology, 2021

The analysis of monthly mean locations of the planetary upper-level frontal zone in the Euro-Atla... more The analysis of monthly mean locations of the planetary upper-level frontal zone in the Euro-Atlantic sector in summer during 1990–2019 is presented. Specific positions for the summer months (June, July, and August) are noted, and maximum northward displacements from the climatological normal for 1961–1990 are found in the years with the formation of the atmospheric blocking. The values of standard deviations of the displacements relative to the normal position were calculated for the summer period of each year both for the North Atlantic, Europe, and the European part of Russia and for the Euro-Atlantic sector. On the basis of linear regression, a tendency is revealed toward an increase in the meridional displacements of the planetary upper-level frontal zone over the recent thirty years and toward the occurrence of maximum deviations over the last decade.

Research paper thumbnail of Clouds and Turbulence Theory: Peculiar Self-Similarity, 4/3 Fractal Exponent and Invariants

Izvestiya, Atmospheric and Oceanic Physics

Research paper thumbnail of Discrete SQG models with two boundaries and baroclinic instability of jet flows

Physics of Fluids

In this paper, new vertically discrete versions of the surface quasigeostrophic (SQG) model with ... more In this paper, new vertically discrete versions of the surface quasigeostrophic (SQG) model with two boundaries are formulated. For any number of partition levels, the equations of the discrete model are written in the form of conservation laws for two Lagrangian invariants, which have the meaning of buoyancy distributions at the horizontal boundaries of the fluid layer. The values of the invariants are expressed in terms of the values of the stream function at two internal levels and contain higher order elliptic operators. The use of discrete models greatly simplifies the solution of problems of the linear theory of hydrodynamic stability and provides high accuracy even with a small number of vertical discrete levels. Using the two-level version of the SQG model, which is similar to the classical two–layer Phillips model, we investigated the linear stability of jet flows induced by piecewise constant boundary distributions of buoyancy. For these flows, analytical expressions for the growth rate of perturbations have been obtained and it is shown that the most unstable perturbation has a wavelength of the order of the Rossby baroclinic radius of deformation. Flows with vertical shear induced by smooth and slowly varying boundary buoyancy distributions are also considered. The instability of these flows is found to be absolute, that is, independent of the velocity profile horizontal structure.

Research paper thumbnail of On eddy viscosity in helical turbulence

Research paper thumbnail of Helicity in the atmospheric boundary layer

EGU General Assembly Conference Abstracts, Apr 1, 2017

Research paper thumbnail of On the helicity estimation in the atmospheric boundary layer

Research paper thumbnail of Experimental studies of the aerosol spectrum at high-mountain conditions

IOP Conference Series: Earth and Environmental Science, 2021

The paper considers variations in the number concentration of submicron aerosols, and size distri... more The paper considers variations in the number concentration of submicron aerosols, and size distribution of aerosol particles on the Shadzhatmaz plateau. The aerosol dimensional spectra were plotted according to the data obtained during hours with no cloudy factors in the atmosphere, and for the measurement periods when the clouds descended so low that the cloud masses were carried by the wind directly through the measurement site. A characteristic feature of the spectrum obtained in the presence of low foggy clouds is the decrease in the fraction of the smallest aerosols (0.1-0.2 μm), compared with the measurement in clear atmosphere conditions; at the same time, the concentration of larger aerosols (0.2 μm and more) under conditions when the observer noted the movement of cloud masses through the measurement site, turned out to be higher than that for clear atmosphere conditions.

Research paper thumbnail of Vertical helicity flux as an index of interannual atmospheric variability

IOP Conference Series: Earth and Environmental Science, 2020

As an index of interannual climatic variability of the atmosphere, it is proposed to calculate th... more As an index of interannual climatic variability of the atmosphere, it is proposed to calculate the weighted average over the hemisphere area (to the pole from latitude 20°) of the vertical helicity flux across the upper boundary of the planetary boundary layer, which is determined by the product of the Coriolis parameter and the square of the wind speed at this boundary. In practical calculations, the data of reanalyses ERA-Interim and ERA-20C on the wind speed at the isobaric level of 850 hPa were used. The statistical distribution of the Earth’s surface area on the helicity flux values, as well as the informational entropy of this distribution, are calculated. It is shown that the introduced index usefully characterizes the interannual climate variability of the atmosphere in both hemispheres.

Research paper thumbnail of Conduction current density profile transformation near the earth’s surface, in connection with atmospheric stratification change

Journal of Physics: Conference Series, 2020

The paper considers physical conditions that influence the formation of vertical profiles of the ... more The paper considers physical conditions that influence the formation of vertical profiles of the conduction current density in the surface atmosphere. The proximity of the earth’s surface, which is a source of radioactive emanations and aerosols, determines the significant variability of atmospheric-electrical characteristics in height. The results obtained made it possible to identify the features of the conduction current density vertical profiles transformation with regard to the atmosphere stratification. The study of the weather conditions dynamics at the observation point, as well as the study of the conduction current density profile variability makes it possible to determine the nature of the influence of meteorological parameters on the process of charge transfer and accumulation in the studied layer.

Research paper thumbnail of Estimation of submicron aerosols influence on the electrical conductivity of the atmosphere surface layer

Journal of Physics: Conference Series, 2020

Research paper thumbnail of Study of transport of atmospheric admixtures and temperature anomalies using trajectory methods at the A.M. Obukhov Institute of Atmospheric Physics

IOP Conference Series: Earth and Environmental Science, 2019

Research paper thumbnail of Dynamics and blocking of Rossby waves in quasi-two-dimensional shear flows

Research paper thumbnail of The role of helicity in turbulent MHD flows

Journal of Experimental and Theoretical Physics, 1998

ABSTRACT

Research paper thumbnail of Expeditionary research of electrical processes on a high mountain plateau taking into account aerosols and humidity

IOP Conference Series: Earth and Environmental Science, 2021

The work continues the analysis of the results of complex expeditionary measurements in the surfa... more The work continues the analysis of the results of complex expeditionary measurements in the surface atmosphere, some of which have recently been published. It uses data from expeditions of the Laboratory of Geophysical Research of the Faculty of Physics of the Southern Federal University at research stations of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences: 2017 at the Tsimlyansk Research Station in the steppe zone, 2018 and 2019 at the Kislovodsk alpine station located on the Shadzhatmaz plateau, 2.100 m above sea level. With the help of regression analysis, empirical relationships of the electric potential gradient near the earth’s surface and the concentration of aerosols with a diameter of more than 0.1 μm were obtained for four measurement periods. The investigated dependence has a linear character. Judging by the results obtained, the space charge of aerosols for the arid steppe zone is negative. For the Shadzhatmaz plateau, the results indicate the presence of a positive space charge in the atmosphere under high humidity conditions. The discovered facts are considered as a consequence of the differences in the physicochemical properties of aerosol particles under different conditions. Proceeding from the results of measurements at the alpine station, regression analysis revealed a close relationship between the concentration of aerosols and relative humidity for different size ranges of particles, which is well approximated by an exponential function.

Research paper thumbnail of Four-thirds law of energy and magnetic helicity in electron and Hall magnetohydrodynamic fluids

Physica D: Nonlinear Phenomena

Research paper thumbnail of Influence of nonlinear interactions on the development of instability in hydrodynamic wave systems

Journal of Experimental and Theoretical Physics, 2016

The problem of the development of shear instability in a three-layer medium simulating the flow o... more The problem of the development of shear instability in a three-layer medium simulating the flow of a stratified incompressible fluid is considered. The hydrodynamic equations are solved by expanding the Hamiltonian in a small parameter. The equations for three interacting waves, one of which is unstable, have been derived and solved numerically. The three-wave interaction is shown to stabilize the instability. Various regimes of the system's dynamics, including the stochastic ones dependent on one of the invariants in the problem, can arise in this case. It is pointed out that the instability development scenario considered differs from the previously considered scenario of a different type, where the three-wave interaction does not stabilize the instability. The interaction of wave packets is considered briefly.

Research paper thumbnail of Jumber Lominadze (In Honor of His 70th Birthday)

Plasma Physics Reports, 2001

Research paper thumbnail of CALIOP-Based Evaluation of Dust Emissions and Long-Range Transport of the Dust from the Aral−Caspian Arid Region by 3D-Source Potential Impact (3D-SPI) Method

Remote Sensing

The average monthly profiles of the dust extinction coefficient (ε) were analyzed according to th... more The average monthly profiles of the dust extinction coefficient (ε) were analyzed according to the CALIOP lidar data from 2006–2021 for 24 cells (size of 2° × 5°) in the Aral-Caspian arid region (ACAR; 38–48°N, 50–70°E). Using the NOAA HYSPLIT_4 trajectory model and the NCEP GDAS1 gridded (resolution of 1° × 1°) archive of meteorological data, the array of >1 million 10-day forward trajectories (FTs) of air particles that started from the centers of the ACAR cells was calculated. On the basis of the FT array, the average seasonal heights of the mixed layer (ML) for the ACAR cells were reconstructed. Estimates of the average seasonal dust optical depth (DOD) were obtained for ACAR’s lower troposphere, for ACAR’s ML (“dust emission layer” (EL)), and for the lower troposphere above the ML (“dust transit layer” (TL)) above each of the ACAR cells. Using the example of ACAR, it is shown that the analysis of DOD for the EL, TL and the surface layer (SL; the first 200 m AGL) makes it pos...

Research paper thumbnail of The Relationship between a Surface Electric Field and an Arid Aerosol under Different Wind Conditions

Doklady Earth Sciences

Abstract The relationship between the concentration of an arid aerosol 0.2–0.4 microns in size an... more Abstract The relationship between the concentration of an arid aerosol 0.2–0.4 microns in size and the electric field strength is investigated using field measurements carried out on a desert territory in Kalmykia in 2020. It is shown that the increase and decrease in the electric field strength is associated with a change in the wind velocity and the its direction relating to the dune ridges. An increase in the electric field strength occurs at wind velocity close to the threshold value and when the wind direction is close to the tangent to the crest line of the dune. According to an analytical estimate, the relative change in the electric field strength is proportional to the square of the number of microparticles generated. Free microparticles, pushed up by the electric field from the saltation layer, appear at the moment of accumulation of a critical charge on the saltation particle. Particle charging occurs faster with small bounces of particles, as in the tangential direction or when the wind velocity is close to the threshold. The influence of aeolian ripples on the motion and the height of the jumps of the saltating particles is noted at wind directions of 25°–45° to the crest line, as a weakening of the electric field with an increase in the number of microparticles.

Research paper thumbnail of Turbulent field helicity fluctuations and mean helicity appearance

International Journal of Non-Linear Mechanics, 2012

There are many experiments where nonzero mean turbulent helicity is measured either directly or i... more There are many experiments where nonzero mean turbulent helicity is measured either directly or indirectly. Despite the study of mechanisms of its occurrence, the question of mean helicity generation remains open. In our paper, we explore the emergence of the mean helicity in the turbulent field created by an external random force with zero helicity under a simultaneous external large-scale impact (rotation or homogeneous magnetic field). It is shown that anisotropy (even weak one) results in the appearance of mean helicity and in the emergence of an analog of the diamagnetic effect in the vortex field.

Research paper thumbnail of Planetary Upper-level Frontal Zone in the Euro-Atlantic Sector in Summer in 1990–2019

Russian Meteorology and Hydrology, 2021

The analysis of monthly mean locations of the planetary upper-level frontal zone in the Euro-Atla... more The analysis of monthly mean locations of the planetary upper-level frontal zone in the Euro-Atlantic sector in summer during 1990–2019 is presented. Specific positions for the summer months (June, July, and August) are noted, and maximum northward displacements from the climatological normal for 1961–1990 are found in the years with the formation of the atmospheric blocking. The values of standard deviations of the displacements relative to the normal position were calculated for the summer period of each year both for the North Atlantic, Europe, and the European part of Russia and for the Euro-Atlantic sector. On the basis of linear regression, a tendency is revealed toward an increase in the meridional displacements of the planetary upper-level frontal zone over the recent thirty years and toward the occurrence of maximum deviations over the last decade.

Research paper thumbnail of Clouds and Turbulence Theory: Peculiar Self-Similarity, 4/3 Fractal Exponent and Invariants

Izvestiya, Atmospheric and Oceanic Physics

Research paper thumbnail of Discrete SQG models with two boundaries and baroclinic instability of jet flows

Physics of Fluids

In this paper, new vertically discrete versions of the surface quasigeostrophic (SQG) model with ... more In this paper, new vertically discrete versions of the surface quasigeostrophic (SQG) model with two boundaries are formulated. For any number of partition levels, the equations of the discrete model are written in the form of conservation laws for two Lagrangian invariants, which have the meaning of buoyancy distributions at the horizontal boundaries of the fluid layer. The values of the invariants are expressed in terms of the values of the stream function at two internal levels and contain higher order elliptic operators. The use of discrete models greatly simplifies the solution of problems of the linear theory of hydrodynamic stability and provides high accuracy even with a small number of vertical discrete levels. Using the two-level version of the SQG model, which is similar to the classical two–layer Phillips model, we investigated the linear stability of jet flows induced by piecewise constant boundary distributions of buoyancy. For these flows, analytical expressions for the growth rate of perturbations have been obtained and it is shown that the most unstable perturbation has a wavelength of the order of the Rossby baroclinic radius of deformation. Flows with vertical shear induced by smooth and slowly varying boundary buoyancy distributions are also considered. The instability of these flows is found to be absolute, that is, independent of the velocity profile horizontal structure.

Research paper thumbnail of On eddy viscosity in helical turbulence

Research paper thumbnail of Helicity in the atmospheric boundary layer

EGU General Assembly Conference Abstracts, Apr 1, 2017

Research paper thumbnail of On the helicity estimation in the atmospheric boundary layer

Research paper thumbnail of Experimental studies of the aerosol spectrum at high-mountain conditions

IOP Conference Series: Earth and Environmental Science, 2021

The paper considers variations in the number concentration of submicron aerosols, and size distri... more The paper considers variations in the number concentration of submicron aerosols, and size distribution of aerosol particles on the Shadzhatmaz plateau. The aerosol dimensional spectra were plotted according to the data obtained during hours with no cloudy factors in the atmosphere, and for the measurement periods when the clouds descended so low that the cloud masses were carried by the wind directly through the measurement site. A characteristic feature of the spectrum obtained in the presence of low foggy clouds is the decrease in the fraction of the smallest aerosols (0.1-0.2 μm), compared with the measurement in clear atmosphere conditions; at the same time, the concentration of larger aerosols (0.2 μm and more) under conditions when the observer noted the movement of cloud masses through the measurement site, turned out to be higher than that for clear atmosphere conditions.

Research paper thumbnail of Vertical helicity flux as an index of interannual atmospheric variability

IOP Conference Series: Earth and Environmental Science, 2020

As an index of interannual climatic variability of the atmosphere, it is proposed to calculate th... more As an index of interannual climatic variability of the atmosphere, it is proposed to calculate the weighted average over the hemisphere area (to the pole from latitude 20°) of the vertical helicity flux across the upper boundary of the planetary boundary layer, which is determined by the product of the Coriolis parameter and the square of the wind speed at this boundary. In practical calculations, the data of reanalyses ERA-Interim and ERA-20C on the wind speed at the isobaric level of 850 hPa were used. The statistical distribution of the Earth’s surface area on the helicity flux values, as well as the informational entropy of this distribution, are calculated. It is shown that the introduced index usefully characterizes the interannual climate variability of the atmosphere in both hemispheres.

Research paper thumbnail of Conduction current density profile transformation near the earth’s surface, in connection with atmospheric stratification change

Journal of Physics: Conference Series, 2020

The paper considers physical conditions that influence the formation of vertical profiles of the ... more The paper considers physical conditions that influence the formation of vertical profiles of the conduction current density in the surface atmosphere. The proximity of the earth’s surface, which is a source of radioactive emanations and aerosols, determines the significant variability of atmospheric-electrical characteristics in height. The results obtained made it possible to identify the features of the conduction current density vertical profiles transformation with regard to the atmosphere stratification. The study of the weather conditions dynamics at the observation point, as well as the study of the conduction current density profile variability makes it possible to determine the nature of the influence of meteorological parameters on the process of charge transfer and accumulation in the studied layer.

Research paper thumbnail of Estimation of submicron aerosols influence on the electrical conductivity of the atmosphere surface layer

Journal of Physics: Conference Series, 2020

Research paper thumbnail of Study of transport of atmospheric admixtures and temperature anomalies using trajectory methods at the A.M. Obukhov Institute of Atmospheric Physics

IOP Conference Series: Earth and Environmental Science, 2019

Research paper thumbnail of Dynamics and blocking of Rossby waves in quasi-two-dimensional shear flows

Research paper thumbnail of The role of helicity in turbulent MHD flows

Journal of Experimental and Theoretical Physics, 1998

ABSTRACT

Research paper thumbnail of Expeditionary research of electrical processes on a high mountain plateau taking into account aerosols and humidity

IOP Conference Series: Earth and Environmental Science, 2021

The work continues the analysis of the results of complex expeditionary measurements in the surfa... more The work continues the analysis of the results of complex expeditionary measurements in the surface atmosphere, some of which have recently been published. It uses data from expeditions of the Laboratory of Geophysical Research of the Faculty of Physics of the Southern Federal University at research stations of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences: 2017 at the Tsimlyansk Research Station in the steppe zone, 2018 and 2019 at the Kislovodsk alpine station located on the Shadzhatmaz plateau, 2.100 m above sea level. With the help of regression analysis, empirical relationships of the electric potential gradient near the earth’s surface and the concentration of aerosols with a diameter of more than 0.1 μm were obtained for four measurement periods. The investigated dependence has a linear character. Judging by the results obtained, the space charge of aerosols for the arid steppe zone is negative. For the Shadzhatmaz plateau, the results indicate the presence of a positive space charge in the atmosphere under high humidity conditions. The discovered facts are considered as a consequence of the differences in the physicochemical properties of aerosol particles under different conditions. Proceeding from the results of measurements at the alpine station, regression analysis revealed a close relationship between the concentration of aerosols and relative humidity for different size ranges of particles, which is well approximated by an exponential function.