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The aim of this study is to assess the probability of black carbon (BC) transfer from high-intensity model forest fires in the taiga zone, determine the fields of concentrations and deposition of BC on the ice–snow surface, and assess the BC contribution to climate change in the Arctic. Model regions with the highest probability of large forest fires (the Komi Republic, Krasnoyarsk krai, and the Republic of Sakha (Yakutia)) are selected based on an analysis of remote monitoring data. The probability of a BC cloud from model fires transferring to the snowy-ice surface of the Arctic is analyzed using the HYSPLIT trajectory model. The probability of a particle emitted from the boreal taiga zone to traverse the sea ice-covered part of the Arctic Ocean is found to be between 1–10%. Effects of BC (the balance of shortwave radiation) on the Arctic climate are estimated on the basis of global climate model of the Institute of Numerical Mathematics Russian Academy of Sciences (INM RAS). According to the results of model experiments, the effect of BC on the balance of shortwave radiation from all model fires in the Northern Hemisphere is 0.11 W m–2 under cloudy conditions and 0.21 W m–2 in a clear sky. The estimated effect on the shortwave radiation balance is a 1.5–2% larger income when compared to the scenario without emission sources. The simulation results showed that the effect of BC emissions from forest fires on the ice-covered Arctic region is negligible. [ABSTRACT FROM AUTHOR]

Using a balance model of the snow layer, we estimate the concentration of black carbon (BC) in the snow; then, with the help of radiative transfer model SNICAR, we calculate the snow albedo and radiative forcing (RF) from snow darkening with BC. Data from an ensemble simulation with INMCM5, the 5th version of the climate model of Marchuk Institute of Numerical Mathematics, Russian Academy of Sciences for the period 1998–2002 are used as input, which include snow both on land and on sea ice. The regionally averaged results are compared with other model data and field measurements. [ABSTRACT FROM AUTHOR]

Five 50-year simulations for the 5th version of the climate model of the Marchuk Institute of Numerical Mathematics, Russian Academy of Science (INM RAS), are used to analyze the interannual variability of Arctic stratospheric polar vortex and dates of spring breakup events (springtime transition) in comparison with reanalysis data. Early spring breakup events are accompanied by stronger wave activity in comparison with late ones. Winter seasons with the maximal air volume in the polar stratosphere and conditions sufficient for the formation of polar stratospheric clouds are characterized by relatively early spring breakup events. [ABSTRACT FROM AUTHOR]

The method of stratospheric aerosols (SA) is considered. This is one of the geoengineering methods, which can be used as a supplementary method to stabilize global temperature at the levels accepted by the Paris Agreement in 2015. It is shown that the application of the SA method could keep global temperature at the levels of +2 and +1.5°С above the preindustrial value, which is calculated in the present paper as the mean over the period of 1800–1850. Maintaining global temperature below +2°С till the end of the 21st century under the most conservative greenhouse gas emission scenario (RCP8.5) could require applying the method of stratospheric aerosols in 2041. The stabilization of global temperature at the level of +1.5°С under the same scenario could require the earlier start the SA method application, in 2023. The maximum value of the annual emission of sulfur compounds reached in 2100 under the worst scenarios of greenhouse gas concentration growth will be within the range of 2–5 Mt S, which is several times lower than the Pinatubo SO2 emission in 1991. The model simulations demonstrate that the stabilization of global temperature at the level of +1.5°С by solar radiation modification methods alone is almost unreal. In this case, it would be necessary to start the application of the SA method in three years. [ABSTRACT FROM AUTHOR]

The simulation of stratosphere-troposphere dynamic coupling is considered in five 50-year realizations of ensemble calculations with the 5th version of the INM-CM5 climate model developed in the Marchuk Institute of Numerical Mathematics of Russian Academy of Sciences. The model also includes the ocean model and the improved vertical resolution in the upper stratosphere and lower mesosphere. [ABSTRACT FROM AUTHOR]

The problem of wind-driven circulation in a thin layer of homogeneous viscous rotating fluid is considered. In the limit of small Froude and Burger numbers it is described by two parameters—the Rossby number proportional to the forcing and the Ekman number. For small Ekman numbers and moderate Rossby numbers, the regimes of steady fluid circulation are investigated through numerical simulations of a Kármántype flow. Two different types of steady flows are shown to exist, and their physical interpretation based on a simple analytical model is proposed. A regime diagram on the plane of problem parameters is provided. The simultaneous existence of steady flows of two different types turns out to be possible in some domain of parameters, i.e., there is a dependence of the stationary solution to the problem on initial data. The asymptotic dependence of steady flow characteristics is investigated in the limit of small Ekman numbers. [ABSTRACT FROM AUTHOR]

An analytical investigation of the effect of three-wave resonant interactions with the linearly unstable wave is proposed. We consider the waves in the Kelvin-Helmholtz model, consisting of two fluid layers with different densities and velocities. We suppose that the velocity shear is weakly supercritical, the instability is of the algebraic type, i.e., the amplitude of the unstable wave grows linearly, and the instability occurs within the framework of a single mode. The amplitudes of two other waves taking part in the nonlinear interaction are assumed to be stable. The initial amplitudes of these waves are supposed to be small in comparison with the initial amplitude of the unstable wave. We present an analysis of the system of amplitude equations derived for this case using JWKB-method. As a result, we obtain equations that couple solutions pre- and post-passing the singular point, i.e., the point where the amplitude of the unstable wave has a local minimum. These equations give us the transformation rule of a parameter that characterizes the phase shift between fast and slow waves and defines the behavior of the system. This parameter is constant between two singular points and varies by chance at a singular point. As long as it stays positive, the amplitude of the wave remains limited and performs stochastic oscillations. If this parameter passes over zero, then we leave the region of stabilization and turn out in the region, where the amplitude grows infinitely. Accordingly, the transition to the region of instability happens stochastically. However, if the time interval, when the amplitude remains bounded, is large enough, the proposed scenario can be treated as a partial stabilization of instability. [ABSTRACT FROM AUTHOR]

Mathematical models of physical processes in a vortical flow created by magnetic hydrodynamics in a thin layer of a rotating viscous liquid are proposed. An inverse problem on restoring the electric field vector is stated and studied, an algorithm of its numerical solution is formulated, and results of numerical experiments are presented. [ABSTRACT FROM AUTHOR]

Proves the theorem about the sufficient stability conditions of conventional semi-Lagrangian schemes. Details of a proposed algorithm modification ensuring the absolute scheme stability; Description of the pseudoparticle method; Study of the semi-Lagrangian scheme stability and the algorithm modification.

Five 50-year simulations with version 5 of the INM RAS coupled climate model revealed that the winters with El Niño are characterized by higher Arctic stratospheric temperature as compared to the seasons with La Niña. Lower stratospheric temperature in the Arctic regions as compared to the seasons with negative sea surface temperature (SST) anomalies corresponds to the winter seasons with positive SST anomalies in the North Pacific. [ABSTRACT FROM AUTHOR]

The surface quasigeostrophic (SQG) model is developed to describe the dynamics of flows with zero potential vorticity in the presence of one or two horizontal boundaries (Earth surface and tropopause). Within the framework of this model, the problems of linear and nonlinear stability of zonal spatially periodic flows are considered. To study the linear stability of flows with one boundary, two approaches are used. In the first approach, the solution is sought by decomposing into a trigonometric series, and the growth rate of the perturbations is found from the characteristic equation containing an infinite continued fraction. In the second approach, few-mode Galerkin approximations of the solution are constructed. It is shown that both approaches lead to the same dependence of the growth increment on the wavenumber of perturbations. The existence of instability with a preferred horizontal scale on the order of the wavelength of the main flow follows from this dependence. A similar result is obtained within the framework of the SQG model with two horizontal boundaries. The Galerkin method with three basis trigonometric functions is also used to study the nonlinear dynamics of perturbations, described by a system of three nonlinear differential equations similar to that describing the motion of a symmetric top in classical mechanics. An analysis of the solutions of this system shows that the exponential growth of disturbances at the linear stage is replaced by a stage of stable nonlinear oscillations (vacillations). The results of numerical integration of full nonlinear SQG equations confirm this analysis. [ABSTRACT FROM AUTHOR]

A coupled atmosphere-ocean general circulation model is used to assess the ability of stratospheric climate engineering (CE) in stabilizing global mean temperatures at the threshold level +2 °C compared to pre-industrial conditions. CE impact by solar radiation management ( SRM) method is applied, when temperature threshold (+2 °C) is reached. Injection intensity is adjusted by the model so that calculated global temperature is remained close to the threshold value. We demonstrate that CE temperature stabilization during the 21st century is possible within the range of +2 ± 0.11 °C. Changes of precipitation intensity as well as effect of sharp termination of CE are investigated. [ABSTRACT FROM AUTHOR]