Explore the vast range of titles available.

With the help of numerical modeling and reanalysis data, interactions between the components of the climate system in the Arctic under the conditions of climate warming have been studied. When analyzing the data and results of numerical experiments, the method of expanding fields of state characteristics in terms of empirical orthogonal functions was used. Trends in the atmospheric impact on the ocean–ice system during the warming period and their relationship with trends in future warming projections under the most severe RCP 8.5 scenario in the CMIP-5 project are identified. In addition, numerical modeling revealed a 44-year periodicity in the interaction between the Arctic Ocean circulation and the heat content of the Atlantic water layer: this can be associated with the Atlantic meridional overturning circulation.

Using the data of the INM RAS model, the sensitivity of the characteristics of atmospheric blocking to the dynamics of the Arctic sea ice is investigated. The changes in the duration and intensity of blocking events with a decrease in the Arctic ice amount are estimated. Such mechanisms as decreasing albedo and increasing carbon dioxide concentration are considered. The possibility of using integrated regional enstrophy to assess the stability of a circulation regime is demonstrated on the example of a blocking episode in the Kara Sea.

This paper discusses some results of the study of eddy heat fluxes in the vicinity of a subtropical jet stream. Many large-scale dynamical phenomena in the Earth’s atmosphere are associated with Rossby wave propagation and collapse processes. Here we focus on regions of countergradient eddy heat fluxes in the region of the subtropical jet stream in the Northern Hemisphere associated with Rossby wave overturning. In these regions, we observe meridional energy transfer on the northern flank of the jet stream in the equatorial direction from the ERA-5 reanalysis data and simulation data with the INM-CM4-8 climate model of the Marchuk Institute of Numerical Mathematics of the Russian Academy of Sciences (INM RAS). The entropy production due to horizontal heat transfer becomes negative, because heat is transferred against the temperature gradient, but this is not a violation of the second law of thermodynamics, since the main part of entropy production occurs due to the processes of vertical heat transfer, such as convection, and other irreversible processes. Entropy production is sensitive to land cover, the entropy balance being most related to radiation at the surface. Quantifying the thermodynamic balance of entropy and entropy production is a useful metric for evaluating the interactions of the atmosphere–surface system. Some estimates of entropy production by the surface are presented in this paper. The traditional approach to studying the climate system focuses on the dynamic mechanisms and physical processes responsible for the conversion of energy from one form to another, but an approach based on analyzing the entropy balance of the climate system and especially entropy production is also important.

The processes of planetary wave breaking (Rossby Wave Breaking – RWB) significantly contribute to variability in stratospheric circulation. Employing a previously developed method for identifying RWB, adapted for stratospheric circulation, this study analyzes the climatology and long-term variability of RWB processes in the middle stratosphere. The method is based on the analysis of potential vorticity (PV) contour geometry at the 850-K level using ERA5 data within the PV range 0–400 PVU (Potential Vorticity Units) determined based on PV field climatology. It was demonstrated that RWB processes exhibit intraseasonal peculiarities. Most frequently, waves break in the northern regions of East Asia and the Pacific Ocean from October to December and in April to March. In January and February, no areas with prevailing RWB processes were identified. We obtained a statistically significant increase in the number of RWB for the first half of winter (October–December) and for the end of the winter period (March and April). For midwinter (January and February), insignificant negative trends were obtained. The results of this work can be used to analyze the long-term variations in stratospheric circulation and, in particular, the occurrence of stratospheric anomalies preceding sudden stratospheric warmings.

Potential vorticity (PV) streamers and cutoffs are indicators of Rossby wave breaking (RWB) near the extratropical tropopause. The Rossby wave breaking forms an elongated high-PV stratospheric air tongue that extends to the equator and a tropospheric low PV air tongue that extends to the pole. There are two types of RWB: equatorward and poleward ones. Frequently, PV tongues stretch into narrow filaments, so-called PV streamers that split into PV cutoff vortices. Here the terms stratospheric PV streamer and cutoff refer to stratospheric features of isentropic surfaces (PV > 2 PVU; where 1 PVU = 10−6 K_kg−1 m2_s−1). In this paper, we study a configuration of the potential vortex field using model data. The main areas of RWB in winter and summer are shown. Atmospheric blocking events represent some of the most high-impact weather patterns in the mid-latitudes, but they have often been the cause of unsuccessful future climate projections. In this paper, we have examined the seasonal frequency of global blocking events in relation to a change in the mean EOF index based on some modeling results obtained by using a climate system model, PlaSim-ICMMG-1.0.

Atmospheric blocking is the most common cause of extreme weather conditions. In the present paper, model data are used to investigate the relationship between the Arctic Oscillation index and the characteristics of atmospheric blocking. The dependence of the duration and intensity of blocking on the index (or phase) of the principal mode during its initial period is estimated. A typical blocking episode is considered, and it is shown that increased values of integral regional enstrophy can be an indicator of the change in the dynamic regime.

The response of extra-tropical evergreen and deciduous Russian forest ecosystems to a wide range of atmospheric background conditions is considered. This study is performed by using a land-surface model, JSBACH. Two numerical experiments are carried out: with hotter and more humid (model PLASIM) and more moderate (model INMCM4) atmospheric background conditions. A perturbation in the climate system is set by using the RCP 8.5 climate scenario. The study has shown a geographical redistribution of the extra-tropical evergreen and deciduous forests across Russia as well as an increase in their fractions in some already forested regions. An increase in the gross and net CO2 assimilation and respiration of these types of forest vegetation, as their response to the climatic disturbances, is obtained. However, even under the conditions of extremely intense climatic disturbances the Russian forest ecosystems will continue to act as CO2 sinks.

The paper describes the configuration of the COSMO-Ru6Sib system with a horizontal grid spacing of 6.6 km adapted to regional conditions. The COSMO-Ru2Sib configuration with a horizontal grid spacing of 2.2 km is also considered. The results of modifying this configuration using weather radar data assimilation as well as urban canopy parameterization are presented and discussed. The results of numerical experiments for the COSMO-Ru6Sib with the COSMO and ICON-LAM models as compute kernels are also presented.

Cloud-resolving modeling has been implemented to investigate a lifecycle of two quasi-tropical cyclones (QTCs) over the Black and Mediterranean seas in September 2005 and 2018. The formation of the Mediterranean QTC under the influence of the PV streamer and the problems of predicting this phenomenon are considered. The influence of the mesocyclone wind system on cumulus convection is studied, while mesocyclone winds are assumed to be axisymmetric for simplicity. It has been found for the largest and most intense QTCs that vertical wind shear may lead to the formation of supercellular storms, but to a rather limited extent and as a result of deviations of mesocyclone currents from the axial symmetry. In small intense QTCs, horizontal wind shear can suppress convection over a certain range of distances from the center of a cyclone, leading to a release of latent heat closer to it.

The dynamic barrier is one of the physical characteristics of the polar vortices; it prevents subpolar air masses from penetrating into the vortex and contributes to a temperature decrease inside the vortex in the lower stratosphere. In the presence of a dynamic barrier in winter, chlorine cycle reagents of ozone destruction accumulate on particles of polar stratospheric clouds (PSCs) and heterogeneous reactions occur with the formation of molecular chlorine. Solar radiation over the polar region trigger photochemical reactions that lead to large-scale ozone depletion. When the dynamic barrier weakens in winter, the temperature inside the vortex rises, PSC particles are destroyed, and, thus, the accumulation of chlorine cycle reagents on PSCs is interrupted. The dynamics of the Arctic polar vortex is proposed to be divided into three types according to the character of consequences: (1) a strong vortex, the activity of which results in the formation of an ozone anomaly, (2) a weak vortex with breakdown in winter, marked by a sudden stratospheric warming, and (3) a stable vortex with an episode (episodes) of weakening of the dynamic barrier in winter without ozone depletion in the period from late winter to spring. A characteristic of the dynamic barrier of the polar vortex at all pressure levels from 100 to 1 hPa is presented for the first time and the consequences of its weakening are described. Using the vortex delineation method based on the data of the ERA5 and MERRA-2 re-analyses, it is shown that in all cases when the polar ozone anomaly was not recorded from late winter to spring under the conditions of the stable polar vortex, the dynamic barrier weakened and particles in the PSСs were destroyed in midwinter.