Technique and Results of Measurements of Turbulent Helicity in a Stratified Surface Layer     

B. M. Koprov  V. M. Koprov  O. A. Solenaya  O. G. Chkhetiani  E. A. Shishov 《Izvestiya Atmospheric and Oceanic Physics》2018,54(5):446-455

In August 2014, measurements of the turbulent velocity rotor, turbulent temperature gradient, turbulent helicity, and turbulent potential vortex were performed at the Obukhov Institute of Atmospheric Physics testing ground in Tsimlyansk under different stratification conditions. The measurements were carried out using the technique first used in the Tsimlyansk expedition in 2012 [1]. The measuring facility consisted of four three-component acoustic Gill Windmaster anemometers–thermometers placed at the vertices of a rectangular tetrahedron with a base scale of 0.7 m (in contrast to the experiment in 2012, when the base scale was 5 m). The measuring facility was placed on top of a mast with an adjustable height of 3.5, 5, 13.5, and 25 m and was equipped with a rotator. The temperature profile in the 10–600 m layer was continuously recorded by the Kadygrov microwave profiler [2]. The series of density of instantaneous helicity He = u_i'ω'_i = u₁'ω₁' + u₂'ω'₂ + u₃'ω'₃ and average values of the total and its summands were calculated for 12 daytime and 10 daytime 2-hour intervals. The helicity value averaged over 12 day realizations is about 0.2 m/s², and the average cosine is close to 0.08 ± 0.03. At night, the helicity is estimated as 0.07 ± 0.03 m/s², and the cosine is close to 0.025 ± 0.03. For the abovementioned 12 daytime and 10 daytime 2-hour intervals, the covariance and correlation matrices of temperature components, velocity rotor, velocity, and temperature gradient are calculated. The off-diagonal terms of the covariance matrix exceed by absolute values the diagonal terms several times. Similar characteristics of a potential vortex were estimated in the incompressibility approximation. The systematic error due to spatial averaging of the measured quantities is discussed.  相似文献   

Nonstationary Vortex Streets in Shear Flows     

Kalashnik  M. V.  Chkhetiani  O. G. 《Izvestiya Atmospheric and Oceanic Physics》2019,55(6):602-611

Izvestiya, Atmospheric and Oceanic Physics - Spatially periodic vortex systems that form due to unstable shear flows are called vortex streets. A number of exact and asymptotic solutions of...  相似文献   

Helicity in the upper atmosphere and Ekman-type instabilities     

O. G. Chkhetiani  S. L. Shalimov 《Doklady Earth Sciences》2010,431(1):345-350

Based on a certain analogy between the physical conditions in the region of the upper atmosphere, transitional from the mesosphere to the lower thermosphere (MLT), and the atmospheric boundary layer (ABL), for the first time for the upper atmosphere we obtained helicity estimates and analyzed the Ekmantype instability. The performed calculations of the orientation of the formed periodic structures agree with the experimental data.  相似文献   

Helicity and Turbulence in the Atmospheric Boundary Layer     

Vazaeva  N. V.  Chkhetiani  O. G.  Kurgansky  M. V.  Kallistratova  M. A. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(1):29-46

Izvestiya, Atmospheric and Oceanic Physics - Helicity is inherent in many circulating motions and structures in the atmospheric boundary layer (ABL), where it is continuously reproduced due to the...  相似文献   

Multipoint Measurements of Temperature and Wind in the Surface Layer     

Shishov  E. A.  Solenaya  O. A.  Chkhetiani  O. G.  Azizyan  G. V.  Koprov  V. M. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(3):254-263

Izvestiya, Atmospheric and Oceanic Physics - The results of multipoint measurements of wind-direction pulsations and air temperature in the surface layer on the basis of the Tsymljansk Scientific...  相似文献   

Using the acoustic-pulse conservation law in estimating the energy of surface acoustic sources by remote sounding     

S.?N.?KulichkovEmail author  O.?Ye.?Popov  A.?A.?Mishenin  I.?P.?Chunchuzov  O.?G.?Chkhetiani  N.?D.?Tsybulskaya 《Izvestiya Atmospheric and Oceanic Physics》2017,53(6):603-612

The atmospheric effect on the characteristics of infrasonic signals from explosions has been studied. New methods have been proposed to remotely estimate the energy of explosions using the data of infrasonic wave registration. One method is based on the law of conservation of acoustic pulse I, which is equal to the product of the wave profile area S/2 of the studied infrasonic signal and the distance to the source E_I [kt] = 1.38 × 10^–10 (I [kg/s])^1.482. The second method is based on the relationship between the explosion energy and the dominant period T of the recorded signal, EТ [kt] =1.02 × (Т [s]²/σ)^3/2, where σ is a dimensionless distance used for determining the degree of manifestation of nonlinear effects in the propagation of sound along ray trajectories. When compared to the conventional E_W (Whitaker’s) relation, the advantage of the EI relation is that it can be used for pulsed sources located at an arbitrary height over the land surface and having an arbitrary form of the initial-pulse profile and for any type of infrasonic arrivals. A distinctive feature of the expression for E_Т is that the atmospheric effect on the characteristics of recorded infrasonic signals is explicitly taken into account. These methods have been tested using infrasonic data recorded at a distance of 322 km from the sources (30 explosions caused by a fire that occurred at the Pugachevo armory in Udmurtia on June 2, 2011). For the same explosion, empirical relations have been found between energy values obtained by different methods: E_I = 1.107 × E _W , E _Т = 2.201 × E _I .  相似文献   

On the Structures Observed in Thin Rotating Layers of a Conductive Fluid and the Anomalies of the Geomagnetic Field     

A. E. Gledzer  E. B. Gledzer  A. A. Khapaev  O. G. Chkhetiani  S. L. Shalimov 《Izvestiya Physics of the Solid Earth》2018,54(4):574-586

The results of the laboratory and numerical experiments in circular rotating trays with thin layers of a conductive fluid under the MHD generation of small-scale velocity fields are presented. The configurations of constant magnets for MHD generation were determined based on the numerical calculations with shallow water equations. Both the laboratory and numerical experiments with rotating trays demonstrate the emergence of nonaxisymmetric structures and large-scale near-circular vortices caused by the energy transfer from the system of the externally generated small-scale vortices to the large-scale velocity fields under the action of the Coriolis force. The near-circular vortex has areas with differential rotation when the angular velocity of rotation decreases with the radius. The single large-scale vortices and wide jet flows arise in the regimes of subrotation and superrotation relative to the external rotation depending on its angular velocity. The emergence of the flow structures with the azimuthal wave number m = 2 is demonstrated, and their probable relation to the anomalies of the geomagnetic field observed on the Earth’s surface is considered.  相似文献   

Sodar Sounding of the Atmospheric Boundary Layer: Review of Studies at the Obukhov Institute of Atmospheric Physics,Russian Academy of Sciences   总被引：1，自引：0，他引：1  

M. A. Kallistratova  I. V. Petenko  R. D. Kouznetsov  S. N. Kulichkov  O. G. Chkhetiani  I. P. Chunchusov  V. S. Lyulyukin  D. V. Zaitseva  N. V. Vazaeva  D. D. Kuznetsov  V. G. Perepelkin  G. A. Bush 《Izvestiya Atmospheric and Oceanic Physics》2018,54(3):242-256

Acoustic sounders (sodars) are the simplest and economically most effective devices for the ground-based remote sensing of the lower troposphere. Using sodars, a vast amount of knowledge about the structure and dynamics of the atmospheric boundary layer (ABL) has been obtained. The principal physics of sodar sounding was given by A.M. Obukhov in two short theoretical articles published in the Reports of the USSR Academy of Sciences in 1941: “On the Scattering of Sound in a Turbulent Flow” and “On the Distribution of Energy in the Spectrum of a Turbulent Flow.” In the late 1950s, Obukhov initiated the development of theoretical and experimental studies of sound scattering by turbulence, as well as a practical sodar sounding of the ABL at the Institute of Atmospheric Physics (IAPh). The present work is a short review of sodar applications in studies of the ABL based on results obtained at IAPh in the 1980s–2000s. The results of recent studies of low-level jets and Kelvin–Helmholtz billows in the stable stratified ABL are described in more detail.  相似文献   

Convective aerosol fluxes near the ground surface     

E. B. Gledzer  I. G. Granberg  O. G. Chkhetiani 《Doklady Earth Sciences》2009,426(1):652-657

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Turbulent Helicity in the Atmospheric Boundary Layer     

Otto G. Chkhetiani  Michael V. Kurgansky  Natalia V. Vazaeva 《Boundary-Layer Meteorology》2018,168(3):361-385

We consider the assumption postulated by Deusebio and Lindborg (J Fluid Mech 755:654–671, 2014) that the helicity injected into the Ekman boundary layer undergoes a cascade, with preservation of its sign (right- or alternatively left-handedness), which is a signature of the system rotation, from large to small scales, down to the Kolmogorov microscale of turbulence. At the same time, recent direct field measurements of turbulent helicity in the steppe region of southern Russia near Tsimlyansk Reservoir show the opposite sign of helicity from that expected. A possible explanation for this phenomenon may be the joint action of different scales of atmospheric flows within the boundary layer, including the sea-breeze circulation over the test site. In this regard, we consider a superposition of the classic Ekman spiral solution and Prandtl’s jet-like slope-wind profile to describe the planetary boundary-layer wind structure. The latter solution mimics a hydrostatic shallow breeze circulation over a non-uniformly heated surface. A 180°-wide sector on the hodograph plane exists, within which the relative orientation of the Ekman and Prandtl velocity profiles favours the left rotation with height of the resulting wind velocity vector in the lowermost part of the boundary layer. This explains the negative (left-handed) helicity cascade toward small-scale turbulent motions, which agrees with the direct field measurements of turbulent helicity in Tsimlyansk. A simple turbulent relaxation model is proposed that explains the measured positive values of the relatively minor contribution to turbulent helicity from the vertical components of velocity and vorticity.  相似文献