bluuebunny/crossref_metadata_2025 huggingface dataset:
About the microwave excitation signal formation in the quantum frequency standard on cesium atoms – 133
Authors: Petrov A A , Davydov V V , Shapovalov D V
Published: December 2019

The features of microwave excitation signal formation in the quantum frequency standard on cesium atoms - 133 were determined. To improve the characteristics of microwave excitation signal, a new method for its formation has been proposed taking into account the features we have identified. Studies have shown that the use of this method allow to improving the spectral characteristics and reducing the step of tuning of microwave excitation signal. The obtained experimental results allowed establishing that the use of this method improves the stability of the output signal of the quantum frequency standard on 20%. The features we have identified allow us to expand the possibilities of research aimed at developing new methods and techniques for improving the characteristics of the microwave excitation signal and characteristics of quantum frequency standard output signal.
Features of the transmission of microwave signals in the range of 8–12 GHz in the maritime radar station over fiber-optic communication line
Authors: Fadeenko V B , Pchelkin G A , Davydov V V , Rud’ V Yu
Published: December 2019

The presented work demonstrates a new design of a fiber-optic line of microwave signal transmission for the receiving path of the maritime radar station. The features of microwave signals transmission in the maritime radar station are established. New designs of the transmitting and receiving modules have been developed in view of the established features. The transmitting module is based on the Mach-Zehnder electro-optical modulator. The receiving module contains p-i-n diode that is based on heterostructures. The results of experimental studies are presented.
Evolution of defect structure and indicator of transition to critical state of material
Authors: Damaskinskaya E E , Panteleev I A , Korost D V
Published: December 2019

A feature that allows one to estimate the degree of criticality of the state of the material subjected to the mechanical load has been identified. Two independent non-destructive methods, i.e., acoustic emission (AE) and X-ray computed microtomography (CT), were used at each stage of sample loading. It was found that the energy distribution of AE signals did not always obey to the Guttenberg-Richter law. It was also found that the type of energy distribution of AE signals could be used as an indicator of the state of a deformed material. The exponential function pointed to a non-critical state; the power-law function indicated that the damage accumulation process had passed to the “dangerous” stage. This feature can be used as a physical basis for a new method of non-destructive testing which will allow one to reveal “dangerous” (requiring replacement or repair) spatial regions of objects (constructions, pipelines, etc.).
Polydisperse bubble flows: a study of the bubble cloud evolution by CFD methods
Authors: Chernyshev A S , Schmidt A A
Published: December 2019

The evolution of a polydisperse bubble cloud is analyzed by means of computational fluid dynamics. Gravity-driven bubble flows in a column with a circular cross-section as well as a downward flow in a long vertical pipe are numerically investigated. A method employed in the simulations is based on the Euler-Euler description of the multiphase medium. An inhomogeneous multiple-size group (MUSIG) model is used to describe the bubble size distribution. The formulated approach provides detailed description of the bubble flow structure including variation of the bubble size distribution.
The small parameter method in the problem of the lateral surface shape of the vertical liquid bridge between planes
Authors: Galaktionov E V , Galaktionova N E , Tropp E A
Published: December 2019

The article is devoted to the study of the shape of the vertical liquid bridge between two solid planes with take into account the gravity force. The variation problem statement is given. The parametric form of solution presentation is used. The solution is constructed as a series in powers of a small Bond number. An algorithm for finding zeroth and the subsequent approximations is proposed. A non-uniqueness of the solution is detected. There may be several different profiles of its lateral surface for a fixed height of the liquid bridge. The dependence of the solutions number on the liquid bridge height has been analyzed.
Numerical aspects of wall-distance computation for turbulence modeling
Authors: Kolmogorov Dmitry K.
Published: December 2019

Numerical aspects of the PDE-based approaches to computing the distance-function involved in many RANS models are discussed focusing on solving Eikonal equation written in advection-diffusion form. This approach is implemented and tested within the in-house structured multi-block general purpose CFD code. A technique which allows considerable increasing the robustness of the numerical procedure is proposed and tested on a set of generic 2D geometries (NACA4412 and 30P30N 3-element airfoils, backward-facing step) and more complex 3D configurations (Stanford diffuser and Common Research Model of commercial aircraft). It is shown that this technique permits to avoid convergence problems typically observed for the Eikonal-type equation and to compute the distance-function for all of the tested configurations. The results obtained show high efficiency of the technique and its potential for turbulence computations of industrial flows.
Kelvin probe force gradient microscopy of WSe2 monolayers on Ni
Authors: Borodin B R , Benimetskiy F A , Nyapshaev I A , Alekseev P A
Published: December 2019

This work presents the results of an investigation of WSe2 thin layers on the Ni film by Scanning Probe Microscopy (SPM) methods. To determine surface potential, Kelvin probe force gradient microscopy (KPFGM) was used. Dependences of the surface potential and work function on the number of monolayers of the structure are presented. The band structure and type of doping of the WSe2 monolayer on the Ni film were determined. These data can be important for measuring the number of WSe2 layers by KPFGM and for designing nanodevices because the work function and the surface potential have a strong influence on the operation of such devices.
The effect of post-growth interruption on the formation of InGaAs/GaAs quantum dots obtained by MOVPE
Authors: Salii R A , Mintairov S A , Nadtochiy A M , Nevedomskiy V N , Kalyuzhnyy N A
Published: December 2019

In this work, the study of formation regimes of In0.8Ga0.2As quantum dots on GaAs surface by metallorganic vapour-phase epitaxy has been carried out. The influence of post-growth interruption after the quantum dots deposition on the optical and physical properties of the formed objects has been investigated. It has been established that the interruption time of 2-5 seconds is optimal for the In0.8Ga0.2As/GaAs material system and growth conditions. For the chosen interruption time, the quality of formed quantum dots and their physical sizes were estimated using transmission electron microscopy: lateral size is 10 – 20 nm, height is not exceeding 5 nm and concentration is ∼9.8·1010 cm−2.
Structural transformation of the BiSbTeSe2 topological insulator during Co laser MBE deposition
Authors: Kaveev A.K. , Suturin S.M. , Golyashov V.A. , Kokh K.A. , Tereshchenko O.E.
Published: December 2019

The studies of the structural transformation of BiSbTeSe2 topological insulator during Co deposition were carried out. It was shown that Co, being deposited on BiSbTeSe2(0001) at 330°C, substantially modifies topmost part of the substrate. Reciprocal space mapping studies using RHEED data analysis reveal formation of the well-ordered layer with the modified composition and crystalline structure. It was found that this layer consists of three orthorhombic structural domains oriented at 120° to each other. Each domain has Pmnn space group characteristic fot CoTexSe2-x. The lattice parameters and epitaxial relations were found.
Laser plasma plume parameters for cascade fission of metal micro- and nanodroplets
Authors: Bormatov A A , Kozhevin V M
Published: December 2019

The cascade fission under the action of Coulomb forces of metal droplets charged up to the Rayleigh limit in a vacuum has been well studied and it is widely used in vacuum technology. Experimental works using the laser electrodispersion method showed that such a division can be carried out in the plasma of a laser plasma plume during the process of nanosecond ablation of metals. The previously published analytical model made it possible to work out requirements for plasma parameters, at which droplets can be divided to nanometer scales, but the limits of applicability of this model were not known. In this paper we present a more accurate numerical model for charging metal droplets in a laser plasma plume, which was used to obtain laser plasma parameters for implementation of cascade metal droplet fission. A comparison with the results obtained using the analytical model is presented.
Study of the influence of the ZnO:Al polycrystalline film morphology on the silver nanoparticles formation
Authors: Shirshneva-Vaschenko E V , Sokura L A , Baidakova M V , Yagovkina M A , Snezhnaia Zh G , Shirshnev P S , Romanov A E
Published: December 2019

The paper presents the results of the optical and structural properties studies of samples consisting of ZnO:Al (AZO) oxide films with an intermediate silver nanoparticles layer. Obtaining samples were carried out by the method of sol-gel technology using different types of composition, and the conditions for drying and final annealing of the samples were varied. The study of the samples optical properties consisted of the optical absorption spectra measurements, and their structural properties were determined by X-ray diffraction and small-angle X-ray scattering. Comparison of data obtained from measurements of optical and structural properties of samples confirmed the results obtained from modeling in the Comsol Multiphysics software. X-ray diffraction demonstrated that the AZO films have a polycrystalline structure and are highly textured in the [002] direction. Zinc oxide grains are 10-15 nm. Silver nanoparticles are the comparable with AZO grains and have dimensions of several tens of nanometers. An increase in the annealing temperature of the films leads to a redistribution of silver nanoparticles in the AZO film, the distance between the particles increases. Consequently, the effect of the plasmon eigenmodes of the nanoparticles prevails over the effect of the system of particles oscillations interacting with each other. The analysis of the coatings obtained by the method of small-angle X-ray scattering showed that nanoparticles in the AZO film form an ordered structure.
Effect of Langmuir coating on the localization of excitonic polarization in CdS surface layer
Authors: Korolkova K A , Novak V R , Sel’kin A V
Published: December 2019

Low temperature (T=2K) optical reflection spectra have been studied for the organic-semiconductor structures prepared by deposition of Langmuir-Blodgett films on CdS surface. The spectra are measured in the resonant spectral range of the A

n=1 exciton state in CdS. Theoretical analysis of the spectra is carried out with an account of the spatial dispersion effects and the exciton-free surface “dead” layer. The conclusion has been drawn of the interface localization of the Wannier-Mott exciton due to organic film deposition on the crystal surface.
Investigation of resistive switching effect in nanocrystalline TiO2 thin film for neuromorphic system manufacturing
Authors: Dukhan D D , Tominov R V , Avilov V I , Zamburg E G , Smirnov V A , Ageev O A
Published: December 2019

Effect of resistive switching in TiO2 thin film was investigated. It was shown, resistive switching from high resistance state (HRS) to low resistance state (LRS) has occurred at 3.2±0.2 V, and from LRS to HRS at -2.8±0.5 V. Endurance test shown that HRS decreased from 42.31±5.26 kΩ to 26.45±6.14 kΩ, LRS increased from 2.25±1.15 kΩ to 3.45±1.18 kΩ. HRS/LRS coefficient has decreased from 18.8 to 7.6. Time-stability of TiO2 surface charge was investigated. It was shown, that voltage decreased from 320±21 to 22±5 mV during 90 minutes and square side increased from 3.43±0.12 to 4.12±0.14 µm during 90 minutes. The results can be useful for neuromorphic systems manufacturing based on nanocrystalline TiO2 films.
Effect of iron intercalation on graphene/SiC electronic structure
Authors: Lobanova E Yu , Pronin I I
Published: December 2019

Graphene-based materials are of great interest for spintronics devices. In the present paper, the effect of intercalated iron on the electronic structure of the graphene/4H-SiC(0001) system has been studied in the frame of density functional theory. It is shown that the most energetically favorable position of intercalated Fe atoms corresponds to their location between the buffer layer and the top Si layer of the substrate. Insertion of Fe atoms into the system leads to the spin polarization of the electronic states of carbon. Another effect is that the buffer layer becomes flat and bilayer graphene forms in the system.
Effect of radiation with low degree coherence on the photoinduced light scattering excitation in lithium niobate crystals
Authors: Maksimenko V A
Published: December 2019

Laser radiation with irregular wavefront erases noisy photorefractive gratings in lithium niobate crystals doped with iron. We investigated noisy photorefractive gratings recording and erasing via observing the photoinduced light scattering in LiNbO3:Fe crystal. Also the effect of the incoherent light on the photoinduced light scattering excitation is considered in the paper.
Polariton Bose condensation in microcavity in high magnetic fields
Authors: Kochereshko V P , Platonov A V , Filosofov N G , Savvidis P , Tsintzos S I , Hatzopoulos Z , Besombes L , Mariette H
Published: December 2019

The dependences of the exciton-polariton photoluminescence spectra on the intensity of optical excitation and external magnetic fields are investigated in cylindrical mesas based on high-quality microcavities. It was found that with an increase of the intensity of optical excitation above a certain threshold at sufficiently large magnetic field or with an increase of magnetic fields at constant optical excitation, the distribution of exciton-polaritons over Zeeman sublevels becomes substantially non-Boltzmannian.
Transverse magneto-optical Kerr effect in magnetoplasmonic waveguide structures based on Fe3O4
Authors: Pavlov S I , Pevtsov A B , Dyakov S A , Yavsin D A , Spitzer F , Akimov I , Verbin S Y , Tikhodeev S G , Gippius N A , Nashchekin A V , Bayer M
Published: December 2019

In this study transverse magneto-optical Kerr effect in transmission for the magnetite thin film with gold grating on top was examined theoretically and experimentally. The magnetite films with thickness of 200 nm were fabricated by the laser electrodispersion technique. Arrays of gold stripes with 600 nm period and 350 nm and 500 nm stripe widths were created by lift-off e-beam lithography. It was shown experimentally that the TMOKE enhancement in structures with 350 nm width is attributed to SPP excitation on gold-magnetite surface. TMOKE value δ reaches magnitude of ±5·10−3 at the wavelengths 790 nm and 860 nm at light incidence angles of 8-10° and 12-13°, respectively. In case of 500 nm stripe width, SPP excitation is poor, however δ reaches magnitude of ±6.6·10−3 at angles of incidence more than 20°, that can be associated with the quasiguided mode resonance in such structure.
Observation of magnetization transfer in spin-exchange collisions of cesium and rubidium atoms
Authors: Dmitriev S P , Dovator N A , Kartoshkin V A , Okunevich A I
Published: December 2019

Spin exchange is one of the effective processes for obtaining spin-polarized atoms. Such mechanism of spin polarization is usually used to transmit and observe the longitudinal (along magnetic field) component magnetization of atoms. However, spin-exchange collisions can also lead to the transfer of the transverse component of magnetization, which occurs when the atoms involved in the collisions are exposed to an alternating resonant magnetic field. This article describes experiments to observe the transmission of transverse magnetization between alkali metal atoms 133Cs and 85Rb in spin-exchange collisions. The calculation of the spin exchange in a mixture of Cs and Rb under magnetic resonance conditions gave a qualitative agreement with the experimental results.
The method of polarization filtering for implementation of the optical manipulator
Authors: Shostka N V , Karakchieva O S , Sokolenko B V , Shostka V I
Published: December 2019

The ability to capture and transport micro-objects with the help of light is one of the topical studies in modern optics. Optical tweezers perform manipulations with colloidal and aerosol nano- and microparticles, living cells, individual molecules and atoms, which is widely used in modern science. Optical traps, created on the basis of singular beams, allow capturing live microorganisms for further study using optical microscopy. Such traps have important practical characteristics, such as maintaining a minimum of intensity on the beam axis, which allows to avoid unwanted overheating of the captured object, as well as to keep the object in transverse coordinates. On the other hand, for many practical purposes it is necessary to limit the transmission of the captured object in the longitudinal direction. Finding ways to generate such three-dimensional traps is currently one of the priorities of world optics. In presented work it is shown that polarized vector beams, formed after uniaxial crystal, create bottle beam with dark centre and by varying geometrical and polarization parameters of experimental set-up it is possible to control the bottle beam properties.
The effect of optical density of the flowing liquid on the measurement error of its refractive index
Authors: Grebenikova N M , Davydov V V
Published: December 2019

The main factors responsible for measurement errors in the determining of the refractive index of the flowing fluid are considered. It was found, that the most significant effect on the measurement error have changes in optical density and temperature of the investigated flowing fluid, scattering of radiation in cuvette transducer and wedge shape of the cuvette glass. A new design of differential refractometer has been developed to study the influence of the optical density values of the flowing fluid on the measurement errors. The results of experimental studies are presented.
Investigation of photoelectric properties of CuO / PZT heterostructures in the visible and near IR regions
Authors: Kochunov K.V. , Konoplev G.A. , Mukhin N.D. , Chigirev D.A.
Published: December 2019

The method of formation of copper oxide / lead zirconate titanate (CuO/PZT) heterostructures using RF magnetron sputtering of chemically pure grade copper oxide powder on prepolarized ferroelectric ceramic substrate is considered; the direction of polarization was parallel with the copper oxide film plane. The short-circuit photocurrent in the CuO/PZT samples with different thicknesses under irradiation in the visible and near IR regions was measured. The spectral dependences of the photocurrent were estimated. The maximum photoresponse of the structures was observed at the wavelength of 515 nm.
Spectral dependencies of multijunction solar cells in a wide range of temperatures
Authors: Levina S A , Mintairov M A , Filimonov E D , Shvarts M Z
Published: December 2019

In this paper, triple-junction solar cells of various middle junction thickness are studied. It is shown that in samples with thin layers, an optical coupling between the top and the bottom subcell is possible as well as a direct leakage of external radiation through the middle one. True values of the spectral dependences of the external quantum efficiency are calculated in accordance with the corrective method. The proposed method reveals some difference in the negative contribution of the luminescence and the positive signal results from the light penetration.
An investigation of the generalized model of pyroelectric thermal IR detectors
Authors: Popov A V , Ilyichev E A , Demin G D
Published: December 2019

In our work, a compact model of an infrared radiation detector based on a LiTaO3 pyroelectric material (lithium tantalate) is presented. Based on the developed model, the time-dependent characteristics of the pyroelectric current, voltage and the surface temperature of such detector were calculated. The obtained results can be used in the development of detectors of thermal images of objects operating in the wavelength range from 3 to 15 μm.
Investigation of the converse flexoelectric effect in KTaO3 using the interferometric microscopy method
Authors: Obozova E D , Polushina A D , Zalesskii V G , Syrnikov P P
Published: December 2019

The inhomogeneous strain induced by an external electric field (the converse flexoelectric effect) has been studied in thin KTaO3 single crystal plates by a scanning interferometric microscopy method. It has been shown that the type of inhomogeneous strain (spherical and cylindrical bending) is determined by the direction of the applied field along [001] and [011] crystallographic directions.
Influence of voltage pulse rise-time on initiation and propagation of fast ionization waves in extended capillaries
Authors: Eliseev S , Timshina M , Samokhvalov A , Letunovskaya M , Smirnov A , Sergushichev K , Kalinin N , Belsky D , Burtsev V
Published: December 2019

Creating stable and efficient compact X-ray sources based on fast capillary discharges that do not incorporate preliminary ionization circuits poses additional restrictions on parameters of voltage pulses and capillary geometry. Applying a voltage pulse with a rise rate of the order of 1 kV/ns results in gradual breakdown of non-ionized gas in the capillary which takes the form of an ionization wave that initiates at the powered electrode and propagates with typical velocities of 1 cm/ns. After the wave reaches the grounded electrode, a plasma channel with gradually increasing conductivity is formed. The current onset therefore appears only after a certain time delay after beginning of the voltage pulse. The ratio between the delay and the applied voltage rise-time will eventually influence the current rise rate that defines plasma heating and compression. It is therefore necessary to have the ability to estimate this delay time for a given capillary geometry and understand its dependence on the properties of a voltage pulse. In this work numerical simulations of fast ionization waves created in an extended Al2O3 capillary filled with nitrogen at 2 Torr were performed for cases of voltage pulses of negative polarity with rise-times varying in the range 10-50 ns. The numerical model was based on fluid approach with drift-diffusion approximation for charged particle fluxes. Influence of voltage rise-time on initiation and propagation of a fast ionization wave as well as on consequent rate of current rise is investigated.
Fast scanning probe for the Globus-M2 tokamak
Authors: Tokarev V A , Gusev V K , Khromov N A , Patrov M I , Petrov Yu V , Sakharov N V , Minaev V B , Varfolomeev V I , Telnova A Yu , Shegolev P B , Bakharev N N , Kurskiev G S , Kiselev E O
Published: December 2019

A fast scanning probe which can penetrate inside the separatrix during discharge was developed for Globus-M2. The probe has been designed to move various sensor pins into the scrape-off layer. The driving force is provided by a crank-slider mechanism which is ensured maximum linear speed about 4 m/s. The paper presents probe head and drive system description.
Investigation of plasma jet sources with high kinetic energy
Authors: Goryainov V Yu , Voronin A V , Gusev V K , Novokhatsky A N , Ponyaev S A
Published: December 2019

Results of coaxial and rail electromagnetic accelerators investigation with pulsed gas puffing and different shapes and lengths of electrodes are presented. The influence of an additional magnetic field on accelerator parameters was studied. The method for plasma jet parameters controlling was developed with the use of a piezo-sensor and infrared camera. The plasma jet pressure dependences on the accelerator length and polarity of the electrode voltage, as well as on the distance from accelerator were derived in experiments on the plasma gun test bench. Coaxial plasma gun with the electrode length 220 mm, negative polarity of the central electrode voltage and focusing insert placed into the initial part of the accelerator proved to be most effective. At the output of the accelerator deuterium plasma jet was obtained with flow velocity up to 160 km/s and pressure up to 2 MPa.
Features of the interaction of shock waves with regions of a gas-discharge plasma of different structure
Authors: Lapushkina T A , Erofeev A V
Published: December 2019

The work considers the possibility of influencing supersonic flows and shock-wave configurations by ionizing the propagation medium or flow around by creating a low-current gas discharge of different configurations. The experimental setup is a shock tube with a connected square working chamber with built-in electrodes to create a glow gas discharge of different intensity and uniformity. The process of the passage of a shock wave created in a shock tube through a region of a pre-arranged gas-discharge plasma having a uniform structure or stratified with ionization inhomogeneities of different scale is investigated. The formation of a new shock-wave configuration during the interaction of a shock wave with an ionized medium, as well as a strong distortion of the waveform up to its complete destruction during interaction with ionization-unstable plasma, has been found.
Study of the possibility of sound stimulation of the instability of the flow of chemically reacting gas in the boundary layer
Authors: Baryshnikov A S , Popov P A
Published: December 2019

Stability of plane-parallel and weak curved chemically reacting gas flow is studied. It is shown that for endothermic processes instability is possible for high-frequency disturbances. Instability of flow is not associated with viscous properties of matter. Comparison with previous similar theoretical investigations is made.
Effect of electron collisions on steady states of plasma diodes with an electron potential barrier
Authors: Kuznetsov V I , Pramanik S , Gerasimenko A B , Chakrabarti N
Published: December 2019

Solutions corresponding to steady states of the Pierce diode are derived in the presence of collisions of electrons with background particles and reflection of electrons from the virtual cathode is investigated. Two families of solutions: Bursian and non-Bursian are explored. It is demonstrated that all non-Bursian solutions disappear when the ratio of the average collision frequency to the electron plasma frequency is of the order of 10 %.
PDI observation in RF plasma generation and current drive experiments on Globus-M tokamak
Authors: Konovalov A N , Dyachenko V V , Stepanov A Yu , Khitrov S A
Published: December 2019

This work presents first results of observation of parametric decay instabilities (PDI) in plasma formation and current start-up experiments on the spherical tokamak Globus-M by radiofrequency (RF) waves without use of induction electric field. In these experiments RF power was used for plasma discharge, as well as for current ramp-up. The current direction was determined on the direction of vertical magnetic field. We used RF generator with operational frequency 900 MHz. Spectral analysis of electromagnetic radiation from plasma showed appearance of big number of low frequency oscillations which was excited by pump wave. These spectra are typical for non-linear parametric instabilities. PDI may lead to the redistribution of the incident RF power between secondary waves with frequencies, differing from pump, to abnormal reflection and even to significant change of plasma-wave interaction mechanism. PDI mostly appeared on the current ramp-up phase. Both sidebands with small shift and with large, about half of pump frequency shift were excited. Relation between PDI and discharge parameters was defined.
NTM threshold island width measurements on Globus-M based on the Fitzpatrick heat transport model
Authors: Dudkovskaia A V , Patrov M I , Gusev V K , Kiselev E O , Kurskiev G S
Published: December 2019

We estimate the neoclassical tearing mode (NTM) threshold island width, Wc
, associated with the bootstrap current contribution to the time evolution of the magnetic island. Following the original work by Fitzpatrick, we solve the heat transport equation for the electron temperature distribution with Wc
being the input parameter. The obtained model temperature profile is then fitted to the Globus-M Thomson scattering (TS) data to deduce the actual Wc
value. Due to the relatively low resolution of the Globus-M TS in the island region, we have also adopted ASTRA to provide the benchmarking.
Numerical simulation of a turbulent wake subjected to adverse pressure gradient
Authors: Guseva E K , Strelets M Kh , Breitenstein W , Scholz P
Published: December 2019

Results are presented of high-fidelity scale-resolving simulations of the wake flow exposed to adverse pressure gradient (APG). Specifically, zonal RANS-IDDES computations are performed of the flow model designed and manufactured at the Technische Universität Braunschweig in the framework of a joint German-Russian project “Wake in Adverse Pressure gradient”. The model includes a flat plate as the wake generator and two pairs of thin liner foils creating APG. Results of the computations of mean flow characteristics agree with currently available experimental data and differ from those of the RANS predictions. This suggests the necessity of RANS models improvement which is planned to be done with the use of the combined experimental/numerical database on the mean flow and turbulence statistics of the wake accumulated in the course of the project.
A multi-level climate club with national and sub-national members: theory and application to US states
Authors: Martin Nick , van den Bergh Jeroen C J M
Published: December 2019

The minilateral approach of a climate club of countries has been suggested as an intermediate phase in a transition towards a global agreement that enforces national climate policies through harmonization. To garner critical mass, we propose an extended club configuration including sub-national states or provinces, resulting in a multi-level club. This would allow considerable contributions from important emitters like the US to be brought on board, relevant given its intended withdrawal from the Paris Agreement. We elaborate this idea and clarify potential roles of participants at distinct levels. The concept is operationalized by developing a method for identifying suitable entities at each level that uses a set of likelihood-of-involvement indicators capturing existing carbon dependence, public opinion, government policy and climate coalition membership. Application at the national level identifies a subset of seven of the highest emitting countries representing 21% of global emissions. This rises to 51% assuming that China, the dominant global emitter, could be enticed into the group. Given that US involvement remains unlikely for now, we illustrate selection at the sub-national level for US states. Here, an initial group of 21 states appear as potential members, jointly accounting for 36% of national emissions. An additional group, representing a further 34% of emissions, are potentially receptive to enticement via trade dependencies on four key countries identified within the group of national members. Accordingly, some 70% of US emissions, representing 11% of global totals, may be subject to climate club involvement via a combination of these pathways. While the implementation of such a club requires various political and legal hurdles to be overcome, the ongoing threat of climate change and inadequacies of the Paris Agreement suggest that novel solutions of this kind deserve serious attention from scientists and politicians.
Intensification of summer precipitation with shorter time-scales in Europe
Authors: Hodnebrog Ø , Marelle L , Alterskjær K , Wood R R , Ludwig R , Fischer E M , Richardson T B , Forster P M , Sillmann J , Myhre G
Published: December 2019

While daily extreme precipitation intensities increase with global warming on average at approximately the same rate as the availability of water vapor (∼7%/°C), a debated topic is whether sub-daily extremes increase more. Modelling at convection-permitting scales has been deemed necessary to reproduce extreme summer precipitation at local scale. Here we analyze multi-model ensembles and apply a 3 km horizontal resolution model over four regions across Europe (S. Norway, Denmark, Benelux and Albania) and find very good agreement with observed daily and hourly summer precipitation extremes. Projections show that daily extreme precipitation intensifies compared to the mean in all regions and across a wide range of models and resolutions. Hourly and 10 min extremes intensify at a higher rate in nearly all regions. Unlike most recent studies, we do not find sub-daily precipitation extremes increasing much more than 7%/°C, even for sub-hourly extremes, but this may be due to robust summer drying over large parts of Europe. However, the absolute strongest local daily precipitation event in a 20 year period will increase by 10%–20%/°C. At the same time, model projections strongly indicate that summer drying will be more pronounced for extremely dry years.
A study of feedbacks and the formation of climate trends in the Arctic climate system
Authors: Platov G , Krupchatnikov V , Borovko I
Published: December 2019

The role of the ocean in the response of the climate system to an increase in the atmospheric CO2 concentration is investigated by using a system of numerical models, ICMMG-PlaSim. The results of this study are summarized as follows: a) the ocean, to some extent (up to 20%), contributes to the increase in the annual mean state and to the decrease in the amplitude of seasonal oscillations (by 2-3%), which ultimately leads to insignificant changes in the summer period and to a significant mitigation of winter, b) the ocean stabilizes the annual mean state of the Arctic oscillation, making it practically unchanged with increasing CO2 concentration but, at the same time, contributes to the significant increase in the amplitude of the seasonal cycle of this oscillation, c) the ocean enhances the temperature (or thermal) component of the seasonal variation associated with the appearance of additional areas freed from ice cover, with an additional average increase in the temperature of the atmosphere at the ice edge. Besides, the ocean enhances the seasonal oscillations of this component, so that the summer manifestations become much stronger, d) our tests have revealed that the role of the Arctic dipole under global warming is insignificant. These conclusions, though, may undergo significant changes under a more detailed consideration of carbon cycles in the atmosphere, ocean, and land.
Differences in the formation of blocking processes between the Northern and Southern Hemispheres
Authors: Morozova S V , Polyanskaya E A , Kononova N K , Denisov K E , Letuchiy A V
Published: December 2019

Mechanisms of formation of blocking processes in the Southern Hemisphere are considered. They are compared with analogous mechanisms in the Northern Hemisphere by using daily synoptic maps of the Northern and Southern Hemispheres. It is found that in the circulation mechanisms of the Southern Hemisphere the process of merging of Antarctic and subtropical anticyclones takes place in a completely different way than in the Northern Hemisphere. The main difference is that in the Northern Hemisphere, as a rule, the ridge of an Arctic anticyclone extends to the low latitudes, but in the Southern Hemisphere the ridge of a subtropical anticyclone extends to the high latitudes, towards Antarctica. An assumption is made that such a peculiarity of circulation leads to the fact that the rear of coastal Antarctic cyclones does not receive cold air masses, as in the cyclones of the Northern Hemisphere, but gets warm in comparison with their frontal part.
Global Atmospheric Oscillation in Geopotential Fields of the Free Atmosphere
Authors: Serykh I V , Sonechkin D M , Byshev V I , Neiman V G
Published: December 2019

The three-dimensional structure of geopotential anomalies arising in the troposphere and the lower stratosphere during a Global Atmospheric Oscillation (GAO) is studied. It was previously detected in temperature and pressure fields. It has been established that these anomalies have a high statistical significance. This serves as another formal evidence of the GAO authenticity. In the troposphere (850–100 hPa) and in the lower stratosphere (100–10 hPa) the structure of GAO substantially changes in comparison with the near-surface fields, gradually acquiring a zonal character. Apparently, this is due to the fact that the atmospheric polar tide, caused by the Chandler wobble of the Earth’s poles and lunar-solar nutation, bends around the Earth almost unhindered, experiencing only a small topographical impact from the continents.
Investigation of boreal storm tracks in historical simulations of INM CM5 and reanalysis data
Authors: Vargin P N , Martynova Y V , Volodin E M , Kostrykin S V
Published: December 2019

Ensemble simulations of the 5th version of the INM coupled climate model are employed to analyze the Northern Hemisphere storm track characteristics in the winter season. The results show similar features of the North Atlantic and North Pacific storm tracks that dominate in the Northern Hemisphere in the model simulations and reanalysis data. A composite analysis of the weakening/strengthening of Arctic stratospheric polar vortex events with their influence on the troposphere shows an equatorward/poleward shift in the North Atlantic storm track. As a response to the recent Arctic amplification, a poleward shift in the Pacific storm track and weakening of the North Atlantic storm track have been revealed when comparing two periods: 1998-2014 and 1980-1997.
Climate clusters of Eurasia against the background of global climate change
Authors: Cheredko N N , Tartakovsky V A , Volkov Y V
Published: December 2019

In this paper we suggest a solution to the problem of identifying the patterns of climate system transformations against the background of global climate change by means of studying changes in the pattern of climate classifications. We present an implementation of the objective classification method using an algorithm proposed by us for the territory of Eurasia for two different time intervals corresponding to global temperature trends. The results of applying our approach to temperature series measured at 485 weather stations in Eurasia from 1955 to 2016 are presented. The classification algorithm is based on comparing changes in the phases of the temperature series. A comparative analysis is performed to show changes in the temperature synchronization regime against the background of climate warming and changes in the structure of climate classes as well. The Russian Arctic and Subarctic, South Western Siberia, as well as stations located in mountainous regions of Eurasia, have shown high sensitivity to the changing climate. We believe that our approach will allow the formation of a general view on the phenomenon under study. This approach can be useful for the analysis of observational data, analytical transformations, and climate modelling.
Dynamics of the Arctic polar vortex during the 1984/1985 sudden stratospheric warming
Authors: Zuev V V , Savelieva E S
Published: December 2019

The Arctic stratospheric polar vortex usually forms in October, reaches its peak intensity in December, and decays from February to April. In most cases, the breakdown of the Arctic polar vortex occurs under the influence of vertically propagating planetary Rossby waves. The influence of planetary wave activity on the polar vortex leads to a displacement or breakdown accompanied by a sudden stratospheric warming (SSW). One of the earliest SSWs was observed on December 29, 1984, after which the polar vortex in the lower stratosphere had not fully recovered and existed for less than 3 months since October. In this study, we analyze the dynamics of the stratospheric polar vortex under the influence of planetary wave activity in the winter of 1984-1985.
Influence of various parameters of INM RAS climate model on the results of extreme precipitation simulation
Authors: Tarasevich M A , Volodin E M
Published: December 2019

The results of simulation of extreme weather indices of modern climate by two versions of the INM RAS climate model (INMCM4, INMCM5) are considered. It is shown that the INMCM5 model simulates most of the temperature and average precipitation related indices better, but the simulation results of extreme precipitation related indices are worse. Various precipitation related physical factors in the model are analyzed. A parameterization of vertical mixing of the horizontal velocity components due to large-scale condensation, as well as air resistance acting on falling precipitation, is implemented in the INMCM5. The corresponding model parameters are adjusted. The effect of the adjustments on the simulation results of extreme indices is presented.
Interannual variability of wind stress curl in the Black Sea and its response to changes in prevailing wind frequency
Authors: Shokurova I G
Published: December 2019

The purpose of this study is to identify trends in the long-term variability of the wind stress curl in the Black Sea and to analyze its response to changes in the direction of the prevailing wind flow over the sea. NCEP/NCAR reanalysis (1948–2016) and ERA Interim reanalysis (1979–2016) wind data at 10-m height are used. The temporal and spatial characteristics of the wind stress curl are compared by using these reanalyses with various spatial resolutions. Interannual changes in the wind stress curl are examined with long-term time series data of NCEP/NCAR reanalysis. The wind stress curl seasonal cycle, the dependence of its magnitude on wind direction, and the frequency of wind direction are in good agreement for the two reanalyses. There are multi-year periods of predominant positive and negative anomalies of the curl according to annual mean and winter data. The cyclonic wind stress curl increases in the late 1960s and early 1970s and weakens at the end of the 1990s. There is a weak positive trend in the curl time series in summer. The long-term variations of the wind stress curl are related to changes in the wind frequency of certain directions. High values of positive correlation coefficients have been obtained between the time series of the basin-averaged wind stress curl and the frequency of northeastern, eastern winds, and negative coefficients for the frequency of southwestern, western winds.
Investigation of eddy and advective heat fluxes in the southeastern part of Western Siberia
Authors: Usova E I , Loginov S V , Kharyutkina E V , Martynova Yu V
Published: December 2019

Estimates of seasonally averaged advective and eddy heat fluxes and relative vorticity at the earth’s surface are obtained for the southeastern part of Western Siberia and, in particular, for the Tomsk region (55°-62°N, 74°-90°E) based on daily ERA-Interim reanalysis data with a high spatial resolution. It has been found that, in general, in the early 21st century in the whole region a decrease in advective air transfer is observed in autumn and winter, and an increase in spring and summer. At the same time, the heat fluxes coming to the region from the southern border play a significant role in regulating these changes. For the eddy heat fluxes, the situation is quite similar, in general. In the past few years, there has been a decrease in cyclonic activity and an increase in anticyclonic circulation. Besides, there was a great fluctuation in relative vorticity at the beginning of the 21st century. However, in general, a tendency towards negative values is observed.
Nonlinear interactions of stationary planetary waves during February 2016 sudden stratospheric warming
Authors: Didenko K A , Pogoreltsev A I , Ermakova T S , Shved G M
Published: December 2019

An analysis of nonlinear wave-wave and wave-mean flow interactions has been carried out during a sudden stratospheric warming (SSW) event in February 2016. This approach is based on a study of the perturbed potential enstrophy (Ertel’s potential vorticity squared) balance equation. The results obtained by using UK Met Office reanalysis data are presented. It has been shown that an increase in the nonlinear interactions occurs at higher-middle latitudes of the boreal stratosphere during the SSW. It is noted that it is necessary to include the stationary planetary wave with zonal wave number m=3 in the analysis of major warmings.
The impact of various types of open boundary conditions in numerical simulation of the Black Sea coastal circulation
Authors: Senderov M V
Published: December 2019

An important problem is to obtain a short-term forecast in the Black Sea coastal zone with a high resolution. It is solved on the basis of numerical modeling of ocean circulation. Carrying out simulations that allow reproducing the meso- and submesoscale processes in a reasonable machine time requires a considerable computational power. One of the common ways to solve this problem is to create a regional configuration (a nested domain). This work is performed to study the influence of methods of specifying open boundary conditions. To conduct such a study, a regional configuration corresponding to the southern coast of Crimea with a resolution of 1.5 km is developed. Four short-term numerical experiments are carried out to investigate the influence of various types of open boundary conditions on the simulation results. The results of the simulations have shown that for a correct reproduction of the hydrophysical parameters, barotropic velocities at the open border should not be taken into account. At the open boundary, in the fields of temperature and salinity, there is no numerical noise when using a flow relaxation scheme. The sea level is reproduced correctly when using a Flather-type scheme.
Simulation of the Pacific equatorial thermocline with an ocean general circulation model
Authors: Ushakov K V , Kaurkin M N
Published: December 2019

The reproduction of equatorial thermocline characteristics by numerical models is of great importance for seasonal forecasts, and it is also a key factor in operational ocean forecasting. Due to difficulties in the numerical description of adiabatic eddy processes, the model thermocline is usually diffused and shifted in depth. In this work, we perform a numerical experimental study of the sensitivity of the Pacific equatorial thermocline to horizontal and vertical mixing parameterizations in the INMIO ocean general circulation model. It has been shown that the sharpness and location of the thermocline can be improved by a combined parameterization of eddy mixing and isopycnal diffusion, as well as by proper tuning of the background coefficient of vertical diffusion.