Table of contents

Turbulence, Atmosphere and Climate Dynamics: the International conference dedicated to the centenary of the birth of A.M. Obukhov

S N Kulichkov, O G Chkhetiani and I A Repina

A.M. Obukhov Institute of Atmospheric Physics, Moscow, Russia

E-mail: snk@ifaran.ru

Abstract. The International Conference dedicated to the centenary of the birth of Academician Alexander Mikhailovich Obukhov «Turbulence, Atmosphere and Climate Dynamics» held in Moscow from May 16 to 18, 2018. The topics of the conference covered the following scientific areas: turbulence; geophysical hydrodynamics; atmospheric and climate system dynamics; physics and composition of the atmosphere; air-sea interaction; wave propagation. The conference showed a high scientific level of almost all the presentations. Studies of turbulent, climatic and atmospheric processes are traditionally conducted in our country at the highest level, as evidenced by the publication in high-ranking scientific journals and the active participation of Russian scientists in international programs.

All papers published in this volume of IOP Conference Series: Earth and Environmental Science have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

The formation of the coherent vortical structures in the form of thin pancakes is studied for three-dimensional flows at the high Reynolds regime when, in the leading order, the development of such structures can be described within the 3D Euler equations for ideal incompressible fluids. Numerically and analytically on the base of the vortex line representation we show that compression of such structures and respectively increase of their amplitudes are possible due to the compressibility of the continuously distributed vortex lines. It is demonstrated that this growth can be considered as analog of breaking for the divergence-free vorticity field. At high amplitudes this process has a self-similar behavior connected the maximal vorticity and the pancake width by the Kolmogorov type relation ω_max ∝ l^-2/3. The role of such structures in the Kolmogorov spectrum formation is also discussed.

The ability of state-of-the-art regional climate models (RCMs) to simulate the trends of intense cyclone activity in the Arctic is assessed based on an ensemble of 13 simulations from 11 models from the Arctic-CORDEX initiative. Some models employ large-scale spectral nudging techniques. Cyclone characteristics simulated by the ensemble in winter and summer are compared with the results from four reanalyses (ERA-Interim, NCEP-CFSR, NASA-MERRA2 and JMA-JRA55) in winter and summer for 1981-2010 period.

Natural variability plays a large role in local climate that makes it difficult to detect the local signal of global climate change even on a multi-decadal timescale. Due to this reason, searching for climate indices that are less sensitive to natural variability and more sensitive to global climate change is an important scientific activity. Here, we show that the observed changes in Moscow's continentality index – four percent decrease per degree increase in mean annual temperature – are in line with climate model simulations, and hence they could be attributed to the global climate change, at least in principal.

A three-parameter mixed gamma distribution is applied for characterizing the statistical properties of the fractional cloud cover in the North Atlantic using visual cloud cover reports from voluntary observing ships (VOS) for the period from 1950 to 2017. Seasonal climatologies of the distribution parameters and the cloud cover are analyzed. The PDF-based analysis allows for the identification of the areas with different probability distributions even under the same mean total cloud cover. Analysis of interannual variability shows that in different regions of the North Atlantic, there are noticeable changes in the form of the distribution over time. In some regions, these changes are coincident with significant trends in the total cloud cover and result in changes in the distribution shape.

The variability of radon distribution in the surface atmosphere is investigated by numerical modeling of radon turbulent transport, based on the data of continuous field natural observations. The boundary conditions, including the radon flux from the surface and radon volumetric activity variation near the surface, were set according to the observations. Variations of turbulent diffusion coefficient altitude profiles were calculated by the observations of wind velocity pulsations at two altitudes made synchronously on the same location. The altitude profiles of radon volumetric activity typical for the atmospheric surface layer over the land of middle latitudes are obtained. It is shown that the radon volumetric activities at any altitudes vary concurrently, but the near-surface radon volumetric activity are greater than one at 10 m. The relative difference between them varies from 10 % (near local midnight) to 120 % (near local midday). The most considerable increase of the radon volumetric activity gradient occurs below 2 m.

Complex tethered balloon observations aimed to investigate of mid-latitude atmospheric boundary layer (ABL) electricity including simultaneous measurement of spectral distribution of aerosol particles, radon activity, polar electrical conductivities and atmospheric electric field were conducted in the summer-autumn seasons 2016 and 2017. It is found that vertical profiles of polar electrical conductivities are largely determined by temperature stratification and stability of the ABL. Balloon observations on fixed altitude allowed registering a clear diurnal variation in aerosol concentration, radon activity, polar and total electrical conductivities related to diurnal variation of the ABL stability. Variability ranges for polar electrical conductivities ratio, space charge and atmospheric conduction current densities have been estimated. Results of numerical modeling of diurnal variation of radon activity, polar electrical conductivities and conduction current are presented and compared with the observed ones.

Forming of the North Atlantic multidecadal variability (MDV) remains quite enigmatic. Some studies connect the long-term North Atlantic oceanic variability to transform of the stochastic atmospheric forcing. On the other hand, the intense heat fluxes directed from ocean to atmosphere precede the large-scale positive sea surface temperature (SST) anomalies in the region (and vice versa). The last phenomenon puts some doubts on the stochastic theory and let to suggest that surface heat fluxes play just a passive role as a response to ocean dynamical processes. Analyzing a toy box model and CMIP5 control experiments we have demonstrated that observed phase shifts between SST and surface heat fluxes do not contradict a stochastic theory. The North Atlantic long-term variability can be induced via a transform of the atmospheric random forcing. However, the role of the ocean circulation processes remains crucial for the MDV forming. Specifically, the stochastic excitation of the meridional overturning circulation reproduces observed and model generated MDV. Direct atmospheric impact on SST cannot induce correctly the phase shift between input and output signals.

The problem of remote diagnostics of a "rough" earth surface and dielectric subsurface structures in the shortwave radio wave band is considered. A new incoherent method for estimating the signal-to-noise parameter is proposed. The idea of the method for determining this parameter is that, by having synchronous information about a wave reflected from the ionosphere and about a wave reflected from the earth and the ionosphere (or having passed the ionosphere twice when probing from a satellite), it is possible to extract information about the scattering parameter. The paper presents the results of recording the quadrature components of the signal by means of the ground measuring complex of installation of coherent sounding in the short-wave range of radio waves at the test site of the Moscow State University (Moscow). A comparative analysis is performed and it is shown that according to the analytical (relative) accuracy of the definition of this parameter the new method is an order of magnitude larger than the widely used standard method. Analysis of the analytical errors in the estimation of this parameter allowed us to recommend a new method instead of the standard one. The software for synchronous registration of quadrature components of radio signals of various multiplicities in real time with the formation of a database of experimental data was developed, successfully tested and patented; one of the functions of the software is to protect the computer system from the powerful radiating pulse of the radio transmitter.

The hydrothermodynamics of the flow over a mountain range under the Novorossiysk bora is investigated. A nonlinear, stationary, two-dimensional, analytical model is used. Vertical unlimitedness of the atmosphere is taken into account by representing it in the form of three layers with different hydrostatic stability. The properties of the unperturbed incindent flotation are taken into account throughout the real range of its changes. The characteristics of the air flow at the leeward slope of the streamlined relief are studied. A hypothesis is made that the intensity of bora can be estimated from the speed at the leeward slope of the mountains.

An analytical model describing the evolution of a convective atmospheric boundary layer in marine cold-air outbreaks in the Arctic is presented. The novelty of the model is a detailed description of the baroclinicity associated with the boundary-layer growth and heating. Ekman friction is also taken into account. Thereby, the model describes the evolution of mixed-layer wind components over the ocean. It is shown theoretically that baroclinicity leads either to deceleration or to acceleration of the flow over the ocean, which depends on the direction of the large-scale flow relative to the orientation of the ice edge. Acceleration of the flow leads to a formation of a low-level jet strongly affecting the surface fluxes of heat and momentum. Baroclinicity and the magnitude of the low-level jet are strongest close to the ice edge being proportional to the ocean-ice temperature difference and decays further downwind. Horizontal decay of the low-level jet strength is governed by the airmass transformation length scale which is estimated to be in the order of 500-1000 km for typical cold-air outbreaks. The model solutions are shown to be in good agreement with aircraft observations over the Fram Strait and results of a numerical nonhydrostatic model.

Characteristic values of nine convective instability indices (CII) including parcel and shear parameters and simplified indices are obtained for tornadoes and waterspouts over Northern Eurasia using ERA-Interim data for the 1979–2016 period. Tornado and waterspout data are extracted from a new database collected in IAP RAS. In general, strong and significant tornadoes are associated with higher values of CII, while waterspouts occur for lower values (especially of shear parameters). Magnitudes of CII for Northern Eurasia significant tornadoes are in general concordance with those for tornadoes in Europe and North America. Threshold values that discriminate between weak and significant tornadoes, and between landfalling and non-landfalling waterspouts, were found by maximizing Threat Score metrics for a particular CII index or for a pair of such indices. Shear parameters show the highest skill as it concerns separating significant and weak tornadoes. CIIs show lower skills for separation of landfalling and non-landfalling waterspouts.

Mathematical methods are proposed for comparing the shape of signals with amplitudes distorted by unknown monotonic transformations. These methods are based on the solution of the problems of the best approximation of the signal under analysis to signals of a specified class, and used in estimating the lag time of one fragment of signal with respect to another. Such problems arise, for example, in determining the direction of propagation of a sound wave in the atmosphere. The solution to this problem is based on the assumption that the conditions of the signal detection are different at different spatial points; as a result, the measured signals differ, not only in their lag time but also in nonlinear distortions, such that only the general sape of the signal is preserved: if the amplitude of one signal is the result of a strictly monotonic transformation of the amplitude of another signal, then their shapes are equivalent. In addition, the measurements are accompanied by an additive noise with an unknown dispersion.

Data on the surface NO, NO₂, CO, SO₂, CH₄, and PM₁₀ concentrations measured at 46 stations from 2005 to 2014 in Moscow have been used in studying the characteristic features of their distribution over the city area and their time variations. Both seasonal and interannual variations in pollutant concentrations, as well as their 10-year trends, are closely related with variations in the urban infrastructure and weather conditions. The weekly cycle of the pollutants has been analyzed. Its largest amplitude is 18.9 ± 5.6% for NO. For CO, NO₂, and PM₁₀, the amplitudes amount to 9.3 ± 3.2%, 13.6 ± 2.8%, and 10.9 ± 5.5%, respectively. The weekly variations in CH₄ and SO₂ concentrations are not significant for such large-scale territorial averaging. The emission fluxes of CO, NO_x, SO₂, and CH₄ and their integral emissions from the Moscow megacity have been estimated from multiyear measurements of their surface concentrations and both vertical air-temperature and wind stratifications. During 2005—2014, the annual integral emissions of CO, NO_x, and CH₄ decreased with a rate of -1.9 ± 0.3, -1.7 ± 0.4, and -7.8 ± 3.1 %·yr^-1, respectively, and that of SO₂ increased with a rate of 3.3 ± 2.3 %·yr^-1. The means of integral annual pollutant emissions from Moscow differ slightly from those for other world megacities. The CO emissions coincide with their EDGAR v4.2 inventory values interpolated to the territory of Moscow. However, the EDGAR v4.2 values of NO_x, SO₂ and CH₄ significantly exceed their calculated values.

This study examined the variations in weather and climate comfort in Russia. For retrospective analysis (1980-2015), reanalysis data were used, for the future (2020-2050) were made using calculations on the climatic model of the Marchuk Institute of Numerical Mathematics RAS. The results using the data from the RCP8.5 ("hard" scenario) suggest that in areas with a strongly continental climate winters get more comfortable, but summers get less comfortable. At the same time, there is also a tendency to smooth out and almost complete absence of a seasonal course of comfort. In regions that are characterized by a temperate continental climate there is a tendency to increase comfort in winter, a decline in autumns and springs and almost no changes in the summer. In areas with oceanic type of climate, a decrease in comfort in winters is expected, as well as in autumns and springs.

The main goal of the DELICAT (DEmonstration of LIdar based CAT detection) project was to check the possibility of early detection of clear air turbulence regions by recording the intensity of reverse molecular scattering by means of a specially designed lidar mounted on the aircraft, operating in the ultraviolet range of wavelengths. Flight tests were conducted from July 17 to August 12, 2013 over the western part of Europe and the adjacent maritime territories. Although measurements in a clear sky were preferred, in most cases aerosol clusters of different power were present along the flight paths. Aerosol clusters should be considered as a source of interference, but their observations also provide an opportunity to obtain information on the properties of the aerosol and the spatial-temporal evolution of clusters. In this paper, we give statistics of observations of aerosol clusters in flights, describe the diversity of their types and trace the influence of flight parameters on the observed characteristics of clusters.

By now the problem of estimating statistical characteristics of red-noise processes is not completely developed. However this problem is of considerable importance for statistical climatology because in the recent years extensive literature has been published containing empirical spectra of red-noise type having noticeable regions of a monotonic increase when a time-scale T increases (with a frequency ω decrease). Such spectra are commonly approximated by the functions increasing like ω^-2α, 0 < α < 1 / 2 (red-noise spectra). When dealing with a problem of estimating statistical characteristics of red-noise processes, the estimate errors are to be calculated. As a rule estimate errors become acceptable small when the empirical time series is long enough and asymptotic formulas for the errors can be used. In this paper, we give a list of formulas describing asymptotic behavior of the estimate errors for mean values, covariances, trend parameters, and structure functions for a wide interval of values of α.

Several methods of isolating available mesoscale circulations from high-resolution data are presented. We discuss temporal and spatial filtration as the classical approach, a combined time-space method (based on two independent numerical simulations with different resolution), and a dynamic method (based on the geostrophic approach as a separation criterion between synoptic and mesoscale processes). The results demonstrate that the dynamic distinction method is the most promising one. Decomposition of the velocity field into geostrophic and ageostrophic components is performed. The research was conducted using the long-term high-resolution North Atlantic Atmospheric Downscaling (NAAD) experiment based on the Weather Research and Forecast model (WRF).

Using the aerosol optical depth (AOD) data from the MODIS satellite instruments, the hazes over Eurasia in July 2016 were analyzed. Total area of the haze blanketing was estimated to be approximately 20 million km2, including the Siberian smoke haze (SSH) with a maximum area of 16 million km2, spreaded over European territory of Russia, Kazakhstan and many European countries. The evolution of AOD in SSH has been analyzed. The total mass of smoke at different stages of the SSH evolution was ranged from 1.6 to 3.7 million tons. When using the aerosol index data from the OMI UV measurements, the essential changes in the qualitative composition of smoke aerosol transported away from the fire places at a distance of 1000-2000 km were detected. The average aerosol radiative forcing at the top of the atmosphere and at the stage of maximum development of the SSH was estimated to be -38 W/m2.

The method is proposed for accounting for the long-term serial correlation (autocorrelation) of data in a linear regression problem. A serially correlated residual series is presented as an autoregressive (AR) process of an order, k, that can be much larger than 1, and the autocorrelation (AK) function of the processes is calculated by solving the system of the Yule-Walker equations. Given the AK function, the corresponding AK matrix is constructed which enters the formulas for estimates of regression coefficients and their errors. The efficiency of the method is demonstrated on the base of the multiple regression analysis of data of ground-based measurements of the column NO₂ content at the Zvenigorod Research Station, Russia, and overpass satellite total ozone measurements over the station. Estimates of regression coefficients and their errors depend on the AR order, k. At first the error increases with increasing k. Then it can approach its maximum and thereafter begin to decrease. In the case of NO₂ and O₃ at Zvenigorod the errors more than double in their maxima compared to the beginning values. The decrease in the error stops at larger k if k approaches the value such that the AR process of this order is able to account for important features of the AK function of the residual series. The multiple linear regression model for NO₂ and O₃ observations includes the seasonally dependent linear trends and the effects of the solar cycle, the quasi-biennial oscillation, the North Atlantic and Southern Oscillations, and the Pinatubo volcanic eruption. Annual and seasonally dependent estimates of these effects in NO₂ and O₃ have been obtained taking into account the serial correlation as long as 50 months.

The effects of the 11-year, quasi-biennial, and 27-day cycles of solar activity on dynamical processes in the atmosphere are studied using empirical data and results of numerical model calculations. Estimates of changes during the 11-year solar cycle in the wind velocity, potential vorticity, geopotential and its large-scale zonal harmonics are obtained using the ERA-Interim reanalysis data. Features of the response of these atmospheric parameters to the solar cycle in some areas of the atmosphere are revealed for a whole year and depending on season. The results point to the existence of a reliable statistical relation of large-scale dynamical and thermodynamic processes in the troposphere and stratosphere to the 11-year solar cycle. Based on the results of 200-year measurements, the phase synchronization of decadal variations of the North Atlantic Oscillation index with the 11-year solar cycle have been found within time intervals alternating with 45–50-year periodicity. According to the ERA-Interim data, the quasi-biennial oscillation in the equatorial stratospheric zonal wind velocity is phase-synchronized at the stratopause level (∼50 km) with the quasi-biennial variations of UV solar radiation. The proposed reason of the synchronization may be the the inhomogeneous heating of this layer due to the absorption of UV solar radiation by ozone, the meridional gradient of which changes in harmony with the quasi-biennial solar variations. The effect of the 27-day solar cycle on the characteristics of large-scale zonal wave harmonics of the geopotential in the Northern Hemisphere is analyzed using results of calculations by a 3-dimensional chemistry-climatic model. Noticeable correlations of the amplitude of the planetary wave components in winter in the Northern Hemisphere with the 27-day solar cycle have been found. The strongest response is obtained for perturbations with wave number 1 in the middle and high latitudes of the Northern Hemisphere.

Some physical mechanisms of perturbations of the wind field due to the inhomogeneities of gravity field have been established. The simplest analytical models of stationary linear atmospheric disturbances caused by inhomogeneities in the field of gravity are analyzed. Estimates show that the influence of gravitational force anomalies (GFAs) on the field of motion can be noticeable in some situations.

The article analyzes the common features and differences of "earlier" and "modern" warming observed. The longest-period series of meteorological observations made on the Svalbard archipelago are used. The phases of growth of surface air temperature are studied. It has been shown that "earlier" warming was more significant in comparison with "modern" warming. The most significant anomalies are observed in the winter months in "early" warming, while "modern" warming is recorded throughout the year.

In this paper we review our earlier predictions of progressive "atlantification" of the Nansen Basin, meaning further eastward advance of the sub-polar structural water type along the Atlantic Water pathway. Fast and persistent reduction of sea ice area in the Western Nansen Basin in mid-winter after 2012 confirms the validity of our basic concept and gives some confidence for making cautious projection of future hydrographic and ice conditions in the Eastern Atlantic sector of the Arctic Ocean.

Wavelike motions (similar to Kelvin-Helmholtz billows, KHBs) within the rising inversion layers during the morning transition of the atmospheric boundary layer (ABL) are investigated. The KHBs were depicted in sodar echograms obtained in a rural terrain near Moscow (Russia) in 2011. Power spectra of the intensity of the sodar return signal were calculated from inversion layers and from convective areas underneath. Comparison of the dominant spectral maximums for the inversion and convective parts of the ABL show connection between convective plumes and KHBs.

Abstact. In this paper, we discuss the methods for evaluation of the anisotropy of small-scale atmospheric irregularities using satellite stellar occultation measurements. These methods are based on coherency analysis of bi-chromatic scintillation observed in occultations of double stars and in tangential (horizontal) occultations. These methods are applied to scintillation measurements by two fast photometers of the GOMOS (Global Ozone Monitoring by Occultation of Stars) instrument on board ENVISAT. The estimates of the anisotropy of air density irregularities generated by saturated gravity waves are obtained for altitudes 30-45 km. The anisotropy coefficient varies from 50 down to 10 with decreasing vertical scales from 60 m to 10 m.

Lakes are among the most important natural sources of greenhouse gas methane (CH₄). Although Western Siberia contains numerous thermokarst lakes, lake CH₄ emissions from this region remain unknown. Here we report the results of field measurements of CH₄ fluxes conducted by static chamber method in summer 2016 on thermokarst tundra lake "Ledyanoe". Based on the measured values, we estimated annual diffusive CH₄ emission from the whole lake by using three approaches: one based on experimental data and two others utilizing modeled data and meteorological records. The quantified annual diffusive CH₄ emission following first method was 135 kg C-CH₄ year^-1 (97–197 kg C-CH₄ year^-1 95% confidence interval), whereas annual CH₄ emission according to next two approaches was 150 kg C-CH₄ year^-1 (148–151 kg C-CH₄ year^-1 95% confidence interval) and 131 kg C-CH₄ year^-1 respectively. Such convergence between the results of different methods can be attributed to compliance of estimates with real annual emission.

The simplest shear flow – a two-dimensional (plane) nonstationary mixing layer – is considered. Results obtained from the direct numerical simulation of mixing at the boundary between two compressible gases (of different densities) moving with a tangential velocity shear in the field of strong external acceleration are described. The simulation was performed using the well-known method of large particles for a two-dimensional case. The reliability of calculation results is supported by their comparison with analytical calculations, results obtained from the numerical solution of a similar problem, and experimental data.

The Canonical Transform (CT) method in different modifications is widely employed for processing radio occultation data. The leading idea of the method consists in the transformation of the measured wave field into the diffractionless representation, where the CT amplitude is only defined by the horizontal gradient of the atmospheric refractivity field. In this paper, we develop the theory of the fluctuation of the CT amplitude in the framework of the geometric optics (GO). The GO approximation is based on the Hamilton form of the ray equations, transformed into the representation of the ray impact parameter. The variations of the CT amplitude are defined by the variation of the ray tube cross-section. We derive the expression for the CT amplitude fluctuation spectrum as an operator on the 3-D fluctuation spectrum of the atmospheric refractivity described by the Kolmogorov turbulence model. We perform the numerical simulation using the split-step method, which indicates that the expression for the spectrum is in a good agreement with the simulated amplitude fluctuation. We estimate of the diffraction limit of the GO approximation.

The application of the general Ertel's vorticity theorem to the diagnosis of general atmospheric circulation processes is discussed. The concepts of a modified potential vorticity (PV) and the "PV of the second generation" are used; the latter quantity is obtained by substituting a PV into Ertel's vorticity theorem. The requirement that the "second-generation PV" vanishes when the PV is properly modified leads to the condition for local compensation of the action of heat sources and frictional stresses on the Earth's surface: namely, to the condition of surface air heating / cooling under anticyclonic / cyclonic circulation conditions. The situation with locally uncompensated anomalous wintertime near-surface air heating over the Barents Sea is discussed in the context of the current reduction in the ice cover over the Arctic, which at the global level should be compensated by the intensification of anticyclonic circulation systems over the continents and the corresponding surface air cooling.

The effect of clouds, wind speed and long-wave radiative balance on the surface and near-surface air temperature in the Arctic during polar night is presented. The most pronounced bimodality in frequency distributions of the cloud fraction corresponding to cloudy and clear-sky situations is found for the stations NP-35 (2007-2008), NP-37 (2009-2010) and NP-38 (2010-2011). A strong impact of the presence or absence of clouds on the air-surface temperature difference is shown. For clear-sky situations nonmonotonic dependency of near-surface air temperature on wind speed is found.

The methodical approach to an assessment of trends of long-range pollution of atmosphere for the ecologically significant zones in view of predicted climatic changes is formulated. Zonal and meridional pollution indices are introduced, which characterize the amount of transported impurities in the latitudinal and meridional directions. The features of the dynamics of long-range atmospheric pollution of the territories of the Russian Federation (RF) under current conditions, in the immediate and distant prospects taking into account the changing climate (from 1980 to 2050) are studied. The results indicate for some strengthening in 2015-2050 compared to the period 1980-2015 the contribution of the west-eastern impurity transport to atmospheric pollution over the northwestern part of the European territory of Russia (ETR), the center of Western and Eastern Siberia, most of the Far East and the Arctic zone of Russia above 70º N and the contribution of the southern impurity transport to atmospheric pollution over the center and southern part of the ETR and the southeastern territories of the Far East. These results are important for the development of proposals for ensuring the environmental safety of Russian regions and for planning economic development of the country's territories that affect the pollution of the environment of ecologically significant zones.

A new informative and evident criterion for estimating the integral helicity is introduced - the gradient of integral helicity. On the example of a convective storm in Moscow on May 29, 2017, its prognostic property is shown (lead time is 12 hours). Its applicability as a prognostic indicator of adverse and dangerous weather phenomena is shown.

Analysis of an interaction between long-term ice cover and atmosphere in different regions of the Arctic Ocean is conducted. For comparison the energy exchange characteristics in the western and eastern periphery of the Beaufort Gyre, the central part of the Arctic Ocean and in the area to the north of the Kara and Barents seas have been analyzed. The results of calculations based on special observations at Russian drifting station "North Pole-4" and its interpretation using a simple thermodynamic model of sea ice were used. As modern in situ data, meteorological observations at drifting stations "North Pole-35" (2007-2008) and "North Pole-39" (2011-2012) were used. Calculations of turbulent heat fluxes in the region of the drift of the American station "SHEBA" were performed. A good agreement between the calculated fluxes based on the historical data and NP-39 data for the summer period is shown. Monthly mean values and standard deviations of meteorological parameters for winter period are presented on the basis of data from drifting stations "North Pole-35" – "North Pole-40" (2007-2013).

In this study, we present the configuration and validation of the third generation spectral wave model WAVEWATCH III with ST6 physics adjusted for high-resolution wind wave hindcast in the North Atlantic based on 14-km winds from non-hydrostatic numerical weather prediction system WRF-ARW (Weather Research and Forecasting). The adjustment of the wave model consists in obtaining the drag coefficient scaling required for WRF winds based on the sensitivity tests and validated against satellite altimetry data. The wave model validation includes analysis of wind sea and swell components compared to directional wave spectra from NDBC buoy data for 2010. The preliminary results of high-resolution WAVEWATCH-WRF hindcast (1979-2017) are discussed with the focus on mean and extreme values of wind sea and swell in winter season (JFM) in 1979-2000. The mean values of wind sea amount up to 5.5 m with the areas of the largest values and mean wave direction reflecting the corresponding characteristics of the wind. Swell heights amount up to 3.2 m with the area of the largest values being displaced westward relative to the wind sea characteristics.

We investigated the variations in the temperature regime, atomic oxygen, and ozone concentrations during the 2013 January major sudden stratospheric warming (SSW) and the 2017 February minor SSW. Data from the spectrometric observations of the hydroxyl emission at the longitudinally spaced mid-latitude sites Tory (51.8° N, 103.1° E) and Zvenigorod (55.7º N, 36.8º E), SABER TIMED satellite measurements and MERRA reanalysis were analysed. Concentrations of the atomic oxygen and ozone at the OH emission layer were calculated by using experimental data on the emission intensity and rotational temperature of the OH molecule, photochemical model of OH radiation, and MSISE-E-90 model. Significant changes in the OH temperature and emission intensity, as well as in the concentrations of atomic oxygen and ozone during the SSWs were revealed. These effects may be caused by variations in the height of the hydroxyl emission layer due to the enhancement of vertical motion in the atmosphere during the SSW. We found an increase in the day-to-day variability of the mesopause temperature up to 3 times in comparison with the mean seasonal values. This may indicate the SSW-associated intensification of the manifestation of the traveling planetary waves activity in the upper atmosphere.

The tendencies of contemporary global and regional climate changes are characterized using long-term data and model simulations in comparison with paleoclimatic reconstructions. The features of climate change in the Arctic and in different Russian regions are noted. The processes that contribute to the climate "nervousness" are considered. The roles of natural and anthropogenic factors in climate change are determined, as well as the ability of numerical models to adequately assess climate change. Global and regional climate trends and their consequences in the 21st century are assessed.

A new algorithm is proposed for solving the k-omega turbulence equations embedded in the Ocean general circulation model (OGCM). Both the circulation and turbulence models are solved using the splitting method with respect to physical processes. We split the turbulence equations into the two stages describing transport–diffusion and generation–dissipation processes. At the generation–dissipation stage, the equation for omega does not depend on turbulent kinetic energy (TKE) k. It allows us to solve both turbulence equations analytically. The technique allows us to use the same time step as in the OGCM that ensures high computational efficiency. The OGCM has a horizontal resolution of 0.25 degree and 40 sigma-levels along the vertical. The coupled model is used to simulate the hydrophysical fields of the North Atlantic and Arctic Ocean. Using the analytical solution for the k-omega turbulence model increases adequacy in reproducing oceanic characteristics by varying coefficients of this solution in numerical simulations. We present the assessments of sensitivity to variations in TKE inflow at the ocean surface. A high sensitivity of the ocean vertical structure to variations in the analytical solution coefficients is revealed at the generation–dissipation stage. In the analytical solution, we use the stability function obtained with solving the Reynolds equations. This improves reproduction of the Arctic upper desalination layer and North Atlantic and Nordic Seas upper quasi-homogeneous layer depth, comparing to using the simple form of the Prandtl number dependence on the Richardson number.

Previously, it was shown that the time lag between changes in global temperature T and atmospheric CO₂ content q_CO2 generally does not characterize cause-and-effect relationships in the Earth system. In particular, in the case of non-greenhouse radiative forcing the sign of this lag depends on the time scale of the forcing. In this paper, the time lag between changes in T and q_CO2 under the external emissions of CO₂ and CH₄ into the atmosphere is studied. It was found that if the time scale of external emissions is large enough changes in q_CO2 are lagging the corresponding changes in T, though the former is the main cause of the latter.

It is shown that the known experimental synoptic spectra of the atmospheric turbulence (spectrum of Van der Hoven, 1957; spectrum of Kolesnikova, Monin, 1965) represent the sum of the solitary spectra of coherent structures with various sizes (with variety outer scales). The spectrums registered by us near to a mirror of the Baikal Solar Vacuum Telescope (BSVT) of the Baikal astrophysical observatory and in a under dome room of the Big Alt-Azimuth Telescope (BTA) of the Special astrophysical observatory are presented too. Apparently, the good coincidence of theoretical spectrums with experimental data (from both parties from a micrometeorological maximum) is observed. This spectrum well approximates the experimental spectrums not only in the field of a micrometeorological interval of frequencies, but also on frequencies of lower, than a micrometeorological maximum where the observational spectrums have decrease.

Here we present the results of measurements of the atmospheric methane concentration and its isotope composition (δ¹³C_CH4) in the East Arctic and Far East Seas during the cruise in the autumn 2016 by two different types of analyzers. Open path LI-7700 and LI-7500 analyzers measuring correspondingly methane (CH₄), and carbon dioxide (CO₂) and water vapor (H₂O) have high time resolution (10Hz) that allow to fix instantaneous values of gas concentration. We obtained high CH₄ concentration (more than 8 ppm) at the location of methane bubbles yields from sea water to atmospheric air. However, due to contamination and icing of the mirrors of these analyzers, significant part of data was rejected for analysis. The data sets of contact gas analyzer G2132-i shows good reliability but the peaks of CH₄ concentration obtained by G2132-i are lower (up to 3.7 ppm) and longer due to instrument's slower responding time. For 10-min averaging, data sets of both CH₄ analyzers gives good agreement, the differences between two types measurements of methane values are less then analyzers' accuracy.

The results of studies of atmospheric aerosol over the territory of Russia are of great interest from the point of view of ecological and climatic problems. The paper presents the results of spatial and temporal variability of Aerosol Optical Depth (AOD) over the European territory of the Russian Federation in the period 1999 – 2016 yy. The assessments were carried out using the original AOD extraction method based on ground-based observations of the Russian actinometric network, and also on the satellite observations of MODIS. The general regularities of spatial variations in the aerosol optical depth over Russia are revealed: a monotonic decrease from the southwest to the northeast with localized areas having different aerosol loads due to the global and regional factors of their formation. The AOT increase in spring and summer is associated with a seasonal increase in temperature and humidity and with changes in the underlying surface. "Purification" of the atmosphere from aerosol is caused by the absence of large volcanic eruptions and by industrial "calm" conditions during the last decade. Negative tendencies are less pronounced in the fall than in spring and summer. To compare the atmospheric AOT values obtained from the MODIS, AERONET and GMS data, we have compiled a combined archive of daily AOT values synchronized in pairs for the 3 types of observations (GMS, MODIS and AERONET): "Aerosol optical thickness of the atmosphere by satellite and ground observations ". The data of the comparison of terrestrial and satellite data for AOD are presented only in averaged form and need further consideration.

The Hasselmann kinetic equation (KE) for stochastic nonlinear surface waves is studied numerically with the aim of searching for features of the Kolmogorov turbulence (KT). To this aim, solutions of the KE for the long-term wave-spectrum evolution are executed. As far as the total wave action N and wave energy E are not preserved simultaneously in the course of the KE solution, two versions of the numerical algorithm are used, preserving values of N or E in separate. In every case, the KE solutions result in formation of the self-similar spectrum shape, S_sf(ω), with the frequency tail S_sf(ω) ∼ ω^-4, independently of the N- or E-fluxes generated by the nonlinear interactions. This urges us to state that the used KE does not obey to regulations of the KT. The reason of this fact resides in the mathematical feature of the kinetic integral, which, in any case of solving the KE, results in formation of the nonlinear energy-transfer tail of kind Nl(ω) ∼ - ω^-4, what stabilizes the spectral tail in form S_Sf(ω) ∼ ω^-4.

Atmospheric tides refer to those oscillations in the atmosphere whose periods are integral fractions of a lunar or solar day. Atmospheric tides are, in small measure, gravitationally forced, they are primarily forced by daily variations in solar insolation. Based on the results of instrumental observations of micropulsations of atmospheric pressure, the main waves of the lunar-solar tide in the Earth's atmosphere are identified. The registration of micropulsations is obtained in the range from 0.1 MHz to 10 Hz in the Geophysical observatory Mikhnevo of Institute of Geosphere Dynamics of Russian Academy of Sciences located in the Moscow region in period 2008-2016. An estimate of the spectral characteristics of micropulsations was carried out using the maximum entropy method. In order to increase the level of discrimination related to the frequencies of tidal waves, the adaptive rejection filtering method was applied. It is shown that the spectral amplitudes with frequencies that coincide with the frequencies of the tidal waves change with time with a periodicity of about 29 days. The characteristics of modulation of the solar elliptic wave S₁ and the main solar wave S₂ by periods of 13.66, 27.55 days are obtained; as well as ∼ 0.3, 0.5 and 1 year.

Observed recovery of the ozone layer likely caused by prohibiting some ozone-depleting substances under the Montreal Protocol is observed since 1998 but still may be unstable. In this regard, the task remains to provide the homogeneity of the ozone observations in comparison with the measurements of previous decades. One of the oldest global systems providing ozone data is the network of fully automated Brewer spectrophotometers which operates since the earlier 1980s. The existing software for control Brewer spectrophotometer was created more than 35 years ago and is in need of redeveloping to maintain long-term observations in the face of changing computer platforms. A new cross-platform control software for the Brewer is under development by a group of researchers from OIAP of RAS. This software is capable for running on computers with modern multitasking operating systems (Windows, Linux, macOS), and at the same time it has one codebase. In the new Brewer control software, the Model/View architecture is implemented to separate the code of measurement data (models) from the code of their display to the user (views). The model is responsible for data management and provides an interface for reading and writing this data, and the view retrieves the necessary data from the model, reacting to its changes, and sends the data to the user, placing them properly in the GUI of application. Models are developed in the C++ programming language using the cross-platform Qt framework, and the relational database SQLite is used as a persistent storage. This software allows improving the quality and uniformity of TOC and UV radiation measurements on the Brewer spectrophotometers of the global ozone network.

The predictability of the widely known phenomenon of El Niño is investigated. For this, the recently found Global Atmospheric Oscillation (GAO) is considered as the main mode of the short-term climatic variations because GAO includes the El Niño – Southern Oscillation process within itself. Three indices characterizing dynamics and interrelation of the extratropical and tropical components of GAO are defined. Among these indices there is one by means of which it is possible to predict El Niño with the lead time of about one year. Generally, it is more, than the lead times of present day hydrodynamical and statistical methods of the El Niño successful forecasting. Then, by means of wavelets, a range of time scales is cleared up in which the closest crosscorrelations exist of this index with an index characterizing El Niño itself.

The spatial and temporal distribution of isoprene and its oxidation products products, such as methyl vinyl ketone (MVK) and methacrolein (MACR) was investigated. The measurements were carried out using by the mobile observatory, placed on the railcar chassis. As the object was selected the vast area of deciduous and mixed forests in Far East, which is crossed by Trans-Siberian Railway. It was shown that the isoprene and MVK and MACR have pronounced daily variations. The isoprene growth at night was not observed. The isoprene and MVK + MACR concentrations are satisfy to a linear regress; the slopes (B) are close to the ∼ 1 (0.93 and 1.04 for TROICA-12 East and West, accordingly). The correlation coefficients (R) are significant and equal to 0.68 and 0.79 for TROICA-12 East and West. The noise of initial 10 sec measured values of MVK + MACR-to-isoprene ratio (below ratio) is significant. The high ratios (> 5) are observed not only at night but also during the day. At night, the high values of ratio somewhat larger than in the daytime. The MVK+MACR and isoprene pair has a high correlation (R∼0.60–0.86) and weak dependence of NO_x, except the one case when the twilight emission of isoprene was dominated.

Based on the trajectory model NOAA HYSPLIT_4 and reanalysis NCEP/NCAR a method for calculating extra large sets (millions of trajectories) of forward and backward trajectories has developed in A. M. Obukhov Institute of Atmospheric Physics (OIAP) of RAS. Using the arrays and trajectory methods, the fields of potential sources of aerosol and gas species are identified. Analyzed are distributions of potential regions of sources of ammonium nitrate, ammonium sulfate, and silicate contributing the surface aerosol, as well as of tropospheric formaldehyde and stratospheric nitrogen dioxide at the Zvenigorod Scientific Station of OIAP, of stratospheric ozone at the Kislovodsk High Mountain scientific Station of OIAP, of column aerosol contents at AERONET stations of Tomsk and Ussuriysk. The method is also applied to identification of remote regions associated with anomalies of winter surface air temperature in Moscow and anomalies of precipitation in the Lake Baikal basin.

Changes in the composition of the atmosphere associated with the atmospheric blocking events were analyzed using the measurements of ozone, water vapor, methane, formaldehyde, carbon monoxide, nitrogen dioxide, as well as aerosol optical characteristics from the satellite instruments OMI, MLS, AIRS, MODIS and MOPITT as well as ground-based, balloon and NCEP/NCAR reanalysis data. The changes in atmospheric composition associated with pyrogenic, biogenic and soil emissions of aerosol and gas constituents as well as the changes due to the regional peculiarities of the large-scale atmospheric dynamics are discussed.

This article studies the contour dynamics of the vortex eye based on the results of laboratory experiments with a differentially rotating shallow fluid. This paper also describes the analysis of the energy processes inside the vortex center with variations in the velocity shift between the center of the system and the periphery in the framework of the instability representations due to the presence of inflection points on the velocity profile. Moreover, it is shown that the conditions for the development of instability arise only at fully determined values of the velocity shift to the width ratio of the shear zone. Finally, articles states that the formation of polygonal configurations of vortex contours with velocity shift is associated with energy transfer.

It has recently been shown that an interesting inverse relationship exists between the strength of the overturning in the regional boreal Hadley circulation and tropical cyclone genesis and lifetime maximum intensity latitudes in the eastern North Pacific. One of the particularly curious aspects of this association is its uniqueness to this ocean basin. We show here that this result can be understood as the outcome of an equatorward shift in the local Intertropical Convergence Zone (ITCZ) and a moderate reduction of tropical vertical shear. These two factors are not necessarily concomitant. The magnitude of the vertical shear change is low enough to suggest that the primary physical mechanism behind this inverse relationship is the equatorward shift in the ITCZ. Since a significant proportion of tropical cyclone genesis results from aggregated convective cells forming into a coherent convective vortex and being shed from the ITCZ, this shift is apparently sufficient to explain the observed association. The equatorward shift in the ITCZ is potentially the result of a relative warming of the Southern Hemisphere in the boreal tropical cyclone season. This more equatorward ITCZ, located over warmer surface waters, presumably explains the more intense Hadley circulation, despite a reduction of the large-scale boreal meridional temperature gradient. Although, these links require further research.

Localized heating in the rotating layer of fluid leads to the formation of intense cyclonic vortex. Cyclonic vortex becomes unstable at low values of viscosity and fast rotation of the experimental model. The instability of the vortex is tightly connected with a structure of the radial inflow. For moderate values of rotational Reynolds number Re the radial flows consist of several branches which transport angular momentum to the center of the model. When Re exceeds critical value (about 23) radial inflow changes its structure and appears as one wide branch which does not reach the center. As a result of strong anisotropy of radial inflow the cyclonic vortex is formed at some distance from the center. Further increase of Re leads to chaotic state with several vortices which appear at different locations near the periphery of the heating area. The map of regimes with stable and unstable vortices is presented.

Recent developments of the unmanned aerial vehicles (UAVs) opens wide opportunities for their application for in-situ meteorological measurements in the atmospheric boundary layer (ABL). In this study we consider the experience of ABL measurements with a mass-market quadcopter DJI Phantom 4 Pro, equipped with temperature, humidity, pressure and infra-red surface temperature sensors. The quadcopter was used during a field experimental campaign in the northern Russia in winter for several types of measurements: hovering near the automatic weather station for a verification (1); vertical transects within the lowest 500 m in order to obtain the vertical temperature profiles and compare them with observations of the microwave temperature profiler MTP-5HE (2); horizontal transects over an unfreezing polynya (3). Additional verification was performed near the high meteorological mast in Obninsk. Listed experiments have shown that quadcopter-based system is a promising and usable tool for ABL measurements. However, its application requires a multi-step data processing framework, which is presented in this study.

Internal gravity waves of different types are frequently observed in the stable atmoshperic boundary layer. The most common way to study the waves is analysis of pressure records. Remote sensing techniques also can be used to observe the waves and to estimate their parameters. We used synchronous sodar and microbarograph records obtained during austral summer at the Antarctic Finnish station Aboa (73.04° S, 13.40° W). Among six wave episodes of different types visible on sodar echograms there was only one in which corresponding pressure oscillations with nearly constant amplitude were present. For three episodes there were pressure oscillation with varying amplitude seemed to be associated with the waves visible on the echograms. For two cases corresponding pressure oscillations were absent.