bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

AbstractAn 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

Abstract
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.
Sensitivity of results of Black Sea level modeling to the choice of boundary conditions on the free surface
Authors: Demyshev S G , Dymova O A , Miklashevskaya N A 
Published: December 2019

Abstract
This work is devoted to an analysis of the influence of sea surface boundary conditions on results of Black Sea level modeling. Two numerical experiments are carried out by using a z-coordinate model of the Marine Hydrophysical Institute, RAS. A linear kinematic condition on the free surface is used for calculating a level rise in the first experiment and a nonlinear one – in the second experiment. The analysis shows that both experiments reconstruct the Black Sea surface dynamics in accordance with altimetry data. It is found that the sea level near the western boundary of the basin decreases under the nonlinear kinematic condition in cases of storm winds. The greatest differences in the structure of the sea level fields are observed during weakening of the RIM Current in the evolution zones of Sevastopol and Batumi anticyclones. The minimal and maximal values of the level are almost identical in both experiments, but the locations do not match. The discrepancies in the spatial positions of raising/lowering levels are due to a mismatch in the motion phases of anticyclones and mesoscale eddies along the periphery of the RIM Current.