Articoli di riviste: "Zonal structures"

1

Falessi, Matteo Valerio, e Fulvio Zonca. "Transport theory of phase space zonal structures". Physics of Plasmas 26, n. 2 (febbraio 2019): 022305. http://dx.doi.org/10.1063/1.5063874.

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Liu, Libo, Yuyan Yang, Huijun Le, Yiding Chen, Ruilong Zhang, Hui Zhang, Wenjie Sun e Guozhu Li. "Unexpected Regional Zonal Structures in Low Latitude Ionosphere Call for a High Longitudinal Resolution of the Global Ionospheric Maps". Remote Sensing 14, n. 10 (11 maggio 2022): 2315. http://dx.doi.org/10.3390/rs14102315.

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This study reports unexpected strong longitudinal structures from Global Navigation Satellite System (GNSS) derived total electron content (TEC) observations in the low-latitude ionosphere over Asia. The observations during 2019–2020 show diverse patterns in the zonal difference of regional TEC, even under geomagnetically quiet conditions. The TEC in the northern hemisphere occasionally exhibits drastic zonal gradients. The intense regional gradients in TEC span a longitudinal extent of about 20°. The higher values may appear on the east or the west side. Strong zonal gradients may appear in all seasons, regardless of geomagnetically quiet or active conditions. The 15 December 2019 and 16 March 2020 cases depict an intense zonal differences cluster in the narrow latitudinal band of 16°N to 28°N, spanning a regional scale smaller than the normal longitudinal structures. In contrast, the Global Ionospheric Maps (GIMs) with a longitudinal resolution of 5° show a much flatter zonal picture. Such intense and regional-scale zonal structures in the low-latitude ionosphere call for a high zonal resolution of GIMs in terms of better geographically distributed observations. Notably, no counterpart regional structures are found at the conjugated points in the southern hemisphere during the two cases. Although the physical drivers are not certain, the appearance only in the northern hemisphere possibly excludes the dominant contribution to forming the regional structures from the equatorial electric field.

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3

Bakas, Nikolaos A., e Petros J. Ioannou. "A theory for the emergence of coherent structures in beta-plane turbulence". Journal of Fluid Mechanics 740 (6 gennaio 2014): 312–41. http://dx.doi.org/10.1017/jfm.2013.663.

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AbstractPlanetary turbulent flows are observed to self-organize into large-scale structures such as zonal jets and coherent vortices. One of the simplest models of planetary turbulence is obtained by considering a barotropic flow on a beta-plane channel with turbulence sustained by random stirring. Nonlinear integrations of this model show that as the energy input rate of the forcing is increased, the homogeneity of the flow is broken with the emergence of non-zonal, coherent, westward propagating structures and at larger energy input rates by the emergence of zonal jets. We study the emergence of non-zonal coherent structures using a non-equilibrium statistical theory, stochastic structural stability theory (S3T, previously referred to as SSST). S3T directly models a second-order approximation to the statistical mean turbulent state and allows the identification of statistical turbulent equilibria and study of their stability. Using S3T, the bifurcation properties of the homogeneous state in barotropic beta-plane turbulence are determined. Analytic expressions for the zonal and non-zonal large-scale coherent flows that emerge as a result of structural instability are obtained. Through numerical integrations of the S3T dynamical system, it is found that the unstable structures equilibrate at finite amplitude. Numerical simulations of the nonlinear equations confirm the characteristics (scale, amplitude and phase speed) of the structures predicted by S3T.

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4

Dorset, Douglas L., Christopher J. Gilmore, Jose Luis Jorda e Stavros Nicolopoulos. "Direct electron crystallographic determination of zeolite zonal structures". Ultramicroscopy 107, n. 6-7 (giugno 2007): 462–73. http://dx.doi.org/10.1016/j.ultramic.2006.05.013.

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5

Ilgisonis, V. I., V. P. Lakhin, N. A. Marusov, A. I. Smolyakov e E. A. Sorokina. "Low-frequency zonal flow eigen-structures in tokamak plasmas". Nuclear Fusion 62, n. 6 (30 marzo 2022): 066002. http://dx.doi.org/10.1088/1741-4326/ac3f4c.

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Abstract The nonlocal eigenmode analysis of low-frequency zonal flows (ZFs) in toroidally rotating tokamak plasmas is performed in the framework of the reduced one-fluid ideal magnetohydrodynamic model. It is shown that for typical profiles of plasma parameters toroidal plasma rotation results in the global ZF formation on the periphery of plasma column. For some types of equilibria these ZFs are aperiodically unstable that leads to the excitation of the differential plasma rotation at the tokamak plasma edge.

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6

Singh, Rameswar, R. Singh, P. Kaw, Ö. D. Gürcan e P. H. Diamond. "Coherent structures in ion temperature gradient turbulence-zonal flow". Physics of Plasmas 21, n. 10 (ottobre 2014): 102306. http://dx.doi.org/10.1063/1.4898207.

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7

SANDBERG, INGMAR, e V. P. PAVLENKO. "Zonal flow in toroidal ion temperature gradient mode turbulence". Journal of Plasma Physics 73, n. 4 (agosto 2007): 565–73. http://dx.doi.org/10.1017/s0022377806004831.

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AbstractThe properties of zonal flows in the toroidal ion temperature gradient mode turbulence are investigated taking into account the polarization drift effects. The stability criterion and the characteristic oscillation frequency of the zonal flow are determined in terms of the spectra of turbulent fluctuations. The nonlinear evolution of zonal flows may lead to the formation of stationary long-lived coherent structures supporting stationary shear layers. These results indicate the existence of regions with reduced levels of anomalous transport attributed to zonal flows generalizing previous findings regarding zonal flows in electron drift turbulence.

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8

Golebiowska, Aleksandra A., e Syam P. Nukavarapu. "Bio-inspired zonal-structured matrices for bone-cartilage interface engineering". Biofabrication 14, n. 2 (25 febbraio 2022): 025016. http://dx.doi.org/10.1088/1758-5090/ac5413.

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Abstract Design and development of scaffold structures for osteochondral (OC) interface regeneration is a significant engineering challenge. Recent efforts are aimed at recapitulating the unique compositional and hierarchical structure of an OC interface. Conventional scaffold fabrication techniques often have limited design control and reproducibility, and the development of OC scaffolds with zonal hierarchy and structural integrity between zones is especially challenging. In this study, a series of multi-zonal and gradient structures were designed and fabricated using three-dimensional bioprinting. We developed OC scaffolds with bi-phasic and tri-phasic configurations to support the zonal structure of OC tissue, and gradient scaffold configurations to enable smooth transitions between the zones to more closely mimic a bone-cartilage interface. A biodegradable polymer, polylactic acid, was used for the fabrication of zonal/gradient scaffolds to provide mechanical strength and support OC function. The formation of the multi-zonal and gradient scaffolds was confirmed through scanning electron microscopy imaging and micro-computed tomography scanning. Precisely controlled hierarchy with tunable porosity along the scaffold length established the formation of the bio-inspired scaffolds with different zones/gradient structure. In addition, we also developed a novel bioprinting method to selectively introduce cells into desired scaffold zones of the zonal/gradient scaffolds via concurrent printing of a cell-laden hydrogel within the porous template. Live/dead staining of the cell-laden hydrogel introduced in the cartilage zone showed uniform cell distribution with high cell viability. Overall, our study developed bio-inspired scaffold structures with structural hierarchy and mechanical integrity for bone-cartilage interface engineering.

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9

Helfrich, Karl R., e Joseph Pedlosky. "Time-dependent isolated anomalies in zonal flows". Journal of Fluid Mechanics 251 (giugno 1993): 377–409. http://dx.doi.org/10.1017/s0022112093003453.

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A theory is developed for time-dependent coherent structures in a marginally stable atmospheric zonal flow. The coherent structures have the form of solitary waves travelling in the zonal direction. Analytical solutions are found for stationary solitary waves but these are shown to be always unstable. The instability manifests itself either as a fission of the structure subsequently emitting two oppositely directed travelling solitary waves or as an implosion in which the structure becomes increasingly more narrow and intense. Which of the two occurs depends sensitively on initial conditions. These solitary waves are stable in head-on collisions only if their joint zonally integrated amplitude is less than a critical value; otherwise, the implosion instability occurs. General initial conditions can give rise to solitary waves which either split, implode, or break down to form a train of nonlinear wave packets. A scenario for the birth and decay of isolated disturbances is given, utilizing the slow parametric transit of the marginal stability curve of the background zonal flow.

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10

Zhou, Yao, Hongxuan Zhu e I. Y. Dodin. "Solitary zonal structures in subcritical drift waves: a minimum model". Plasma Physics and Controlled Fusion 62, n. 4 (10 marzo 2020): 045021. http://dx.doi.org/10.1088/1361-6587/ab78f3.

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11

Sheshadri, Aditi, R. Alan Plumb, Erik A. Lindgren e Daniela I. V. Domeisen. "The Vertical Structure of Annular Modes". Journal of the Atmospheric Sciences 75, n. 10 (ottobre 2018): 3507–19. http://dx.doi.org/10.1175/jas-d-17-0399.1.

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Stratosphere–troposphere interactions are conventionally characterized using the first empirical orthogonal function (EOF) of fields such as zonal-mean zonal wind. Perpetual-winter integrations of an idealized model are used to contrast the vertical structures of EOFs with those of principal oscillation patterns (POPs; the modes of a linearized system governing the evolution of zonal flow anomalies). POP structures are shown to be insensitive to pressure weighting of the time series of interest, a factor that is particularly important for a deep system such as the stratosphere and troposphere. In contrast, EOFs change from being dominated by tropospheric variability with pressure weighting to being dominated by stratospheric variability without it. The analysis reveals separate tropospheric and stratospheric modes in model integrations that are set up to resemble midwinter variability of the troposphere and stratosphere in both hemispheres. Movies illustrating the time evolution of POP structures show the existence of a fast, propagating tropospheric mode in both integrations, and a pulsing stratospheric mode with a tropospheric extension in the Northern Hemisphere–like integration.

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12

Bakas, Nikolaos A., Navid C. Constantinou e Petros J. Ioannou. "S3T Stability of the Homogeneous State of Barotropic Beta-Plane Turbulence". Journal of the Atmospheric Sciences 72, n. 5 (1 maggio 2015): 1689–712. http://dx.doi.org/10.1175/jas-d-14-0213.1.

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Abstract Zonal jets and nonzonal large-scale flows are often present in forced–dissipative barotropic turbulence on a beta plane. The dynamics underlying the formation of both zonal and nonzonal coherent structures is investigated in this work within the statistical framework of stochastic structural stability theory (S3T). Previous S3T studies have shown that the homogeneous turbulent state undergoes a bifurcation at a critical parameter and becomes inhomogeneous with the emergence of zonal and/or large-scale nonzonal flows and that these statistical predictions of S3T are reflected in direct numerical simulations. In this paper, the dynamics underlying the S3T statistical instability of the homogeneous state as a function of parameters is studied. It is shown that, for weak planetary vorticity gradient β, both zonal jets and nonzonal large-scale structures form from upgradient momentum fluxes due to shearing of the eddies by the emerging infinitesimal flow. For large β, the dynamics of the S3T instability differs for zonal and nonzonal flows but in both the destabilizing vorticity fluxes decrease with increasing β. Shearing of the eddies by the mean flow continues to be the mechanism for the emergence of zonal jets while nonzonal large-scale flows emerge from resonant and near-resonant triad interactions between the large-scale flow and the stochastically forced eddies. The relation between the formation of large-scale structure through modulational instability and the S3T instability of the homogeneous state is also investigated and it is shown that the modulational instability results are subsumed by the S3T results.

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13

Chen, L., e F. Zonca. "Nonlinear equilibria, stability and generation of zonal structures in toroidal plasmas". Nuclear Fusion 47, n. 8 (24 luglio 2007): 886–91. http://dx.doi.org/10.1088/0029-5515/47/8/021.

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14

Itoh, K., K. Hallatschek, S. Toda, S.-I. Itoh, P. H. Diamond, M. Yagi e H. Sanuki. "Collisional effects on coherent structures of zonal flows and turbulent transport". Plasma Physics and Controlled Fusion 46, n. 5A (23 aprile 2004): A335—A340. http://dx.doi.org/10.1088/0741-3335/46/5a/037.

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15

Bencze, A., M. Berta, S. Zoletnik, J. Stockel, J. Adámek e M. Hron. "Observation of zonal flow-like structures using the autocorrelation-width technique". Plasma Physics and Controlled Fusion 48, n. 4 (21 marzo 2006): S137—S153. http://dx.doi.org/10.1088/0741-3335/48/4/s10.

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16

Das, Amita, Abhijit Sen, Sangeeta Mahajan e Predhiman Kaw. "Zonal and streamer structures in magnetic-curvature-driven Rayleigh–Taylor instability". Physics of Plasmas 8, n. 12 (dicembre 2001): 5104–12. http://dx.doi.org/10.1063/1.1416483.

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17

Kaw, Predhiman, Raghvendra Singh e P. H. Diamond. "Coherent nonlinear structures of drift wave turbulence modulated by zonal flows". Plasma Physics and Controlled Fusion 44, n. 1 (19 dicembre 2001): 51–59. http://dx.doi.org/10.1088/0741-3335/44/1/305.

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18

Poyrazoglu, Gokturk. "Determination of Price Zones during Transition from Uniform to Zonal Electricity Market: A Case Study for Turkey". Energies 14, n. 4 (15 febbraio 2021): 1014. http://dx.doi.org/10.3390/en14041014.

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In the electricity market, different pricing models can be applied to increase market competitiveness. Different electricity systems use different market structures. Uniform marginal pricing, zonal marginal pricing, and nodal marginal pricing methods are commonly used market structures. For markets wishing to move from a uniform pricing structure to a more competitive zonal pricing structure, the determination of price zones is critical for achieving a competitive market that generates accurate price signals. Three different pricing zone detection algorithms are analyzed in this paper including the k-means clustering and queen/rook spatially constraint clustering. Finally, the results of a case study for the Turkish electricity system are shared to compare each method.

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19

Wang, Bin, e Sun-Seon Lee. "MJO Propagation Shaped by Zonal Asymmetric Structures: Results from 24 GCM Simulations". Journal of Climate 30, n. 19 (1 settembre 2017): 7933–52. http://dx.doi.org/10.1175/jcli-d-16-0873.1.

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Abstract Eastward propagation is an essential characteristic of the Madden–Julian oscillation (MJO). Yet, simulation of MJO propagation in general circulation models (GCMs) remains a major challenge and understanding the causes of propagation remains controversial. The present study explores why the GCMs have diverse performances in MJO simulation by diagnosis of 24 GCM simulations. An intrinsic linkage is found between MJO propagation and the zonal structural asymmetry with respect to the MJO convective center. The observed and realistically simulated MJO eastward propagations are characterized by stronger Kelvin easterly waves than Rossby westerly waves in the lower troposphere, which is opposite to the Gill pattern where Rossby westerly waves are 2 times stronger than Kelvin easterly waves. The GCMs simulating stronger Rossby westerly waves tend to show a stationary MJO. MJO propagation performances are robustly correlated with the quality of simulated zonal asymmetries in the 850-hPa equatorial zonal winds, 700-hPa diabatic heating, 1000–700-hPa equivalent potential temperature, and convective instability. The models simulating realistic MJO propagation are exemplified by an eastward propagation of boundary layer moisture convergence (BLMC) that leads precipitation propagation by about 5 days. The BLMC stimulates MJO eastward propagation by preconditioning and predestabilizing the atmosphere, and by generating lower-tropospheric heating and available potential energy to the east of precipitation center. The MJO structural asymmetry is generated by the three-way interaction among convective heating, moisture, and equatorial wave and boundary layer dynamics. In GCMs, differing convective heating representation could produce different MJO structural asymmetry, and thus different propagations. Diagnosis of structural asymmetry may help revealing the models’ deficiency in representing the complex three-way interaction processes, which involves various parameterized processes.

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Li, Yue, Jiye Wu, Jing-Jia Luo e Young Min Yang. "Evaluating the Eastward Propagation of the MJO in CMIP5 and CMIP6 Models Based on a Variety of Diagnostics". Journal of Climate 35, n. 6 (15 marzo 2022): 1719–43. http://dx.doi.org/10.1175/jcli-d-21-0378.1.

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Abstract Given the climatic importance of the Madden–Julian oscillation (MJO), this study evaluates the capability of CMIP6 models in simulating MJO eastward propagation in comparison with their CMIP5 counterparts. To understand the representation of MJO simulation in models, a set of diagnostics with respect to MJO-associated dynamic and thermodynamic structures is applied, including large-scale zonal circulation, vertical structures of diabatic heating and equivalent potential temperature, moisture convergence at the planetary boundary layer (PBL), and the east–west asymmetry of moisture tendency relative to the MJO convection. The simulated propagation of the MJO in CMIP6 models shows an overall improvement in realistic speed and longer distance, which displays a robust linear regression relationship against the above-mentioned dynamic and thermodynamic structures. The improved MJO propagation in CMIP6 largely benefits from better representation of premoistening processes that is primarily contributed by improved PBL moisture convergence. In addition, the convergence of moisture and meridional advection of moisture prior to the MJO convection are enhanced in CMIP6, while the zonal advection of moisture is as weak as that in CMIP5. The increased convergence of moisture is a result of enhanced lower-tropospheric moisture and divergence, and the enhanced meridional advection of moisture can be caused by sharpened meridional gradient of mean lower-tropospheric moisture in the western Pacific. Further examination of the lower-tropospheric moisture budget reveals that the enhanced zonal asymmetry of the moisture tendency in CMIP6 is driven by the drying process to the west of the MJO convection, which is attributed to the negative vertical and zonal advections of moisture.

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21

Averkina, T. I., e V. T. Trofimov. "Types of engineering geological structures of the Russia territory". Moscow University Bulletin. Series 4. Geology, n. 5 (28 ottobre 2016): 3–15. http://dx.doi.org/10.33623/0579-9406-2016-5-3-15.

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Engineering geological structures are divided by a combination of regional and zonal geological factors. Classifications of engineering geological structures of the Earth and Russia are submitted. Main engineering geological features and regularities of spatial distribution of continental subaerial, continental subaquatic, transitional predominant isubaquatic, and oceanic predominant isubaquatic engineering geological mega- and macrostructures of the Russia have been described.

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Gong, Yuhan, Jiahao Lu e Tian Li. "The Impact of Annual Cycles on Anomalous Wind Meridional Structures of the ENSO". Atmosphere 15, n. 8 (8 agosto 2024): 950. http://dx.doi.org/10.3390/atmos15080950.

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The anomalous zonal wind moves southward during the ENSO mature phase in boreal winter. Previous studies suggest that it may be caused by the nonlinear interaction of annual cycles or the influence of background mean state changes. In this research, the ECHAM4.6 atmospheric model is used to confirm the mechanism of the anomalous zonal wind southward shifting. The annual cycle of solar radiation and SST are removed in the sensitivity experiments to avoid the interaction between the ENSO and annual cycle. The results show that the north–south asymmetry mode of the ENSO anomalous wind field is not the result of a nonlinear interaction between ENSO and the annual cycle. The mean v-winds in winter motivate the southward shifting of the ENSO anomalous wind field through advection.

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Guo, L., e G. Lehmacher. "First meteor radar observations of tidal oscillations over Jicamarca (11.95° S, 76.87° W)". Annales Geophysicae 27, n. 6 (26 giugno 2009): 2575–83. http://dx.doi.org/10.5194/angeo-27-2575-2009.

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Abstract. Tidal oscillations in the equatorial mesosphere and lower thermosphere (MLT) region over Jicamarca (11.95° S, 76.87° W) are studied using the observations from the newly installed Jicamarca All-sky Specular MEteor Radar (JASMET). The vertical structure and seasonal variability of diurnal and semidiurnal tides from 80–100 km are presented. The analyses show a strong diurnal tide over Jicamarca for both zonal and meridional components with the meridional amplitudes being larger than the zonal ones. Maximal diurnal amplitudes, 45 m/s for zonal and 55 m/s for meridional, are observed around equinox. The zonal diurnal amplitudes reach maxima at 90–96 km, while the meridional diurnal amplitudes grow with altitude for most months. Semidiurnal amplitudes vary not as strong as diurnal amplitudes. The vertical structures of the tidal components are compared with Global Scale Wave Model (GSWM02) prediction and the tidal wind analysis results from TIDI measurements onboard of the TIMED satellite. The data from JASMET and TIDI show similar amplitudes for both diurnal and semidiurnal tides. GSWM02 overestimates diurnal amplitudes, but underestimates semidiurnal amplitudes for both zonal and meridional components.

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Koshkin, Konstantin A., e Ilya A. Tatarinov. "Development of Zone Forecast probability Models for Oil and Gas Potential in the Central Part of the Permian Uplift by Structural and Capacity Criteria". Недропользование 21, n. 1 (gennaio 2021): 2–8. http://dx.doi.org/10.15593/2712-8008/2021.1.1.

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The task to which this article is devoted has not received due attention in recent years, since the preparation of structures for deep drilling is carried out using seismic exploration. At the same time, there is a huge array of data on structured drilling, unfortunately, it has not been fully used. Thus, the goal of the study is to use data on structured drilling to solve not only structural problems for marking surfaces, but also more complex ones related to zonal oil and gas potential of territories. The forecast of oil and gas content for marking and oil and gas horizons was carried out in three zones of oil and gas geological zoning. Using the data on these territories, studies were carried out to build probabilistic models for the zonal forecast of oil and gas content. To substantiate the joint use of data on marking surfaces and data on the tops of oil-bearing horizons, materials were studied for 447 deep wells. Probabilistic models of zonal forecast of oil and gas content of the central part of the Permian uplift were developed according to structural and capacity criteria. The complex use of data on the absolute marks of deep and structured wells made it possible to rank the territory of the central part of the Permian uplift by the degree of zonal oil and gas content. Severokamskoye (0.73), Krasnokamskoye (0.67), Baklanovskoye (0.67), Polaznenskoye (0.67), Rassvetnoye (0.64) and Mezhevskoye (0.63) fields were characterized by the maximum values of P COM. For the Kozubaevskoye field, the P COM was 0.57. The Gorskoye, Lobanovskoye, Talitskoye, Zorinskoye and Shemetinskoye fields were characterized by minimum values of P COM, varying in the range of 0.51–0.53. This scheme can be used when designing prospecting and exploration works in this area.

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Beebe, Reta F. "Growth and dispersion of the Shoemaker-Levy 9 impact features from HST imaging". International Astronomical Union Colloquium 156 (maggio 1996): 307–28. http://dx.doi.org/10.1017/s0252921100115568.

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The Hubble Space Telescope Wide Field Planetary Camera 2 imaging data provide the highest spatial resolution of individual Shoemaker-Levy 9 impact sites. Analysis of images obtained with the F410M filter yielded horizontal translation rates of tropospheric cloud structures and the east-west components have been interpreted as zonal winds which vary with latitude. When the tropospheric zonal winds between —60° and —30°, which were derived from the SL9 images, are compared with Voyager data there are no discernible changes in the magnitude or latitudinal positions of wind minima and maxima. This result provides additional evidence of the long-term stability of the zonal winds. Changes in individual sites during a two week period in July 1994 have been mapped. Their evolution is consistent with zonal winds decreasing with height and it provides evidence that local circulation associated with isolated weather systems perturbs the lower stratosphere.

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Monahan, Adam H., e John C. Fyfe. "On the Nature of Zonal Jet EOFs". Journal of Climate 19, n. 24 (15 dicembre 2006): 6409–24. http://dx.doi.org/10.1175/jcli3960.1.

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Abstract Analytic results are obtained for the mean and covariance structure of an idealized zonal jet that fluctuates in strength, position, and width. Through a systematic perturbation analysis, the leading empirical orthogonal functions (EOFs) and principal component (PC) time series are obtained. These EOFs are built of linear combinations of basic patterns corresponding to monopole, dipole, and tripole structures. The analytic results demonstrate that in general the individual EOF modes cannot be interpreted in terms of individual physical processes. In particular, while the dipole EOF (similar to the leading EOF of the midlatitude zonal mean zonal wind) describes fluctuations in jet position to leading order, its time series also contains contributions from fluctuations in strength and width. No simple interpretations of the other EOFs in terms of strength, position, or width fluctuations are possible. Implications of these results for the use of EOF analysis to diagnose physical processes of variability are discussed.

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Katsura, Shota, Hiromichi Ueno, Humio Mitsudera e Shinya Kouketsu. "Spatial Distribution and Seasonality of Halocline Structures in the Subarctic North Pacific". Journal of Physical Oceanography 50, n. 1 (gennaio 2020): 95–109. http://dx.doi.org/10.1175/jpo-d-19-0133.1.

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AbstractThe spatial distribution and seasonality of halocline structures in the subarctic North Pacific (SNP) were investigated using Argo profiling float data and various surface flux data collected in 2003–17. The permanent halocline (PH) showed zonal patterns in the spatial distributions of its depth and intensity and tended to be shallow and strong in the eastern SNP but deep and weak in the west. Mean distributions of PH depth and intensity corresponded to the winter mixed layer depth and sea surface salinity, respectively, indicating that it forms in association with the development of the winter mixed layer. In the Western Subarctic Gyre and Alaskan Gyre, where a relatively strong PH formed, PH intensity and depth showed clear seasonal variations, and deepening of the mixed layer compressed the underlying PH during the cooling period, resulting in intensification and development of the PH in late winter. In both regions, upwelling of high-salinity water also contributed to PH intensification. The summer seasonal halocline (SH) showed distinct zonal differences in frequency and intensity, which were opposite to the PH distribution. While an SH formed in the western and central SNP and coastal regions, it was seldom present in the eastern area. This zonal contrast of SH corresponded to freshening of the mixed layer during the warming period, primarily reflecting freshwater flux. Geostrophic and Ekman advection play important roles in spatial differences in SH intensity and depth. SH development contributed to PH intensification in the following winter, by decreasing salinity above the PH through entrainment.

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Zhou, Yao, Hongxuan Zhu e I. Y. Dodin. "Formation of solitary zonal structures via the modulational instability of drift waves". Plasma Physics and Controlled Fusion 61, n. 7 (23 maggio 2019): 075003. http://dx.doi.org/10.1088/1361-6587/ab16a8.

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Onishchenko, O. G., e O. A. Pokhotelov. "Generation of zonal structures by internal gravity waves in the Earth’s atmosphere". Doklady Earth Sciences 445, n. 1 (luglio 2012): 845–48. http://dx.doi.org/10.1134/s1028334x12070070.

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Li, Ling, Mingshun Yuan e Quanming Li. "Zonal embedded grids for LES of self-sustaining structures of wall turbulence". Tsinghua Science and Technology 15, n. 5 (ottobre 2010): 555–60. http://dx.doi.org/10.1016/s1007-0214(10)70100-0.

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Qiu, Zhiyong, Liu Chen e Fulvio Zonca. "Nonlinear excitation of finite-radial-scale zonal structures by toroidal Alfvén eigenmode". Nuclear Fusion 57, n. 5 (24 marzo 2017): 056017. http://dx.doi.org/10.1088/1741-4326/aa6413.

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Goncharova, I. A., L. N. Skripalshikova e A. P. Barchenkov. "Floristic analysis of birch coenosis in Krasnoyarsk forest-steppe". Проблемы ботаники Южной Сибири и Монголии 19, n. 1 (2 giugno 2020): 98–102. http://dx.doi.org/10.14258/pbssm.2020020.

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The flora composition of the of birch coenosis in Krasnoyarsk forest-steppe has been studied. Thetaxonomic, chorological, belt-zonal, ecological, biomorphological structures of flora are determined. Species to beprotected have been discovered.

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33

Kantorovich, Ye G. "Equilibrium Models of Spatial Interaction with Locational-Capacity Constraints". Environment and Planning A: Economy and Space 24, n. 8 (agosto 1992): 1077–95. http://dx.doi.org/10.1068/a241077.

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Two types of equilibrium models of urban spatial structures are considered. An equilibrium version of the production-constrained spatial interaction model involving zonal-capacity constraints on allocation is investigated. A model of equilibrium for interacting subsystems is defined (it is a generalisation of Nash equilibria and of some Lowry-type models) and connections between this model and Nash equilibria are investigated. An entropy-projection operator is used for equilibrium urban models with zonal-capacity constraints. Problems of uniqueness of an equilibrium and the convergence of the iterative computational process are studied for these models.

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34

Cash, Benjamin A., Paul J. Kushner e Geoffrey K. Vallis. "Zonal Asymmetries, Teleconnections, and Annular Patterns in a GCM". Journal of the Atmospheric Sciences 62, n. 1 (1 gennaio 2005): 207–19. http://dx.doi.org/10.1175/jas-3361.1.

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Abstract The influence of zonally asymmetric boundary conditions on the leading modes of variability in a suite of atmospheric general circulation models is investigated. The set of experiments consists of nine model configurations, with varying degrees and types of zonal asymmetry in their boundary conditions. The structure of the leading EOF varies with the zonal asymmetry of the base state for each model configuration. In particular, a close relationship is found between the structure of the EOF and the model storm tracks. An approximately linear relationship is found to hold between the magnitude of the zonal asymmetry of the leading EOF and of the storm tracks in the models. It is shown that this linear relationship extends to the observations. One-point correlation maps centered on the regions where the EOFs reach their maximum amplitude show similar structures for all configurations. These structures consist of a north–south dipole, resembling the observed structure of the North Atlantic Oscillation (NAO). They are significantly more zonally localized than the leading EOF, but do resemble one-point correlation maps and sector EOFs calculated for a simulation with zonally symmetric boundary conditions. Thus, the leading EOF for each simulation appears to represent the longitudinal distribution of zonally localized NAO-like patterns. This longitudinal distribution appears to be tied to the distribution of high-frequency eddies, as represented by the storm tracks. A detailed momentum budget for each case confirms that high-frequency eddies play a crucial role in producing the NAO-like patterns. Other dynamical processes also play an important role, but vary with the details of the simulation.

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35

Sekar, R., D. Chakrabarty, R. Narayanan e A. K. Patra. "Equatorial Spread F structures and associated airglow intensity variations observed over Gadanki". Annales Geophysicae 26, n. 12 (2 dicembre 2008): 3863–73. http://dx.doi.org/10.5194/angeo-26-3863-2008.

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Abstract. Co-ordinated campaigns have been conducted from Gadanki (13.5° N, 79.2° E, dip lat 6.4° N) by operating simultaneously the Indian MST radar in ionospheric coherent backscatter mode and by monitoring thermosphere airglow line emissions (630.0 nm and 777.4 nm) using a narrow band multi-wavelength scanning photometer during January-March for the past five years (2003–2007) and also during April 2006, as a special campaign. Simultaneous radar and optical observations reveal optical signatures corresponding to a variety of equatorial spread F (ESF) structures. The optical signatures corresponding to ESF structures with wave-like bottomside modulations with plasma plumes, confined bottomside flat and wavelike structures, vertically extended plume structure in the absence of bottomside structure apart from the classical plasma depletions and enhancements are obtained during these campaigns. The plasma depletions and enhancements were identified using optical measurements. In addition, estimations of zonal wavelength of the bottomside structures and the inference of shears in the zonal plasma drift in the presence of confined structures, were carried out using bi-directional airglow measurements. Furthermore, it is found that the vertical columnar intensity of OI 630.0 nm airglow exceeded the slanted columnar intensity in the presence of large bottomside structure. The need for the appropriate physical mechanisms for some of the ESF structures and their characterizations with optical observations are discussed.

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36

Le Dizès, Stéphane. "Wave field and zonal flow of a librating disk". Journal of Fluid Mechanics 782 (6 ottobre 2015): 178–208. http://dx.doi.org/10.1017/jfm.2015.530.

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In this work, we provide a viscous solution of the wave field generated by librating a disk (harmonic oscillation of the rotation rate) in a stably stratified rotating fluid. The zonal flow (mean flow correction) generated by the nonlinear interaction of the wave field is also calculated in the weakly nonlinear framework. We focus on the low dissipative limit relevant for geophysical applications and for which the wave field and the zonal flow exhibit generic features (Ekman scaling, universal structures, etc.). General expressions are obtained which depend on the disk radius $a^{\ast }$, the libration frequency ${\it\omega}^{\ast }$, the rotation rate ${\it\Omega}^{\ast }$ of the frame, the buoyancy frequency $N^{\ast }$ of the fluid, its kinematic diffusion ${\it\nu}^{\ast }$ and its thermal diffusivity ${\it\kappa}^{\ast }$. When the libration frequency is in the inertia-gravity frequency interval ($\min ({\it\Omega}^{\ast },N^{\ast })<{\it\omega}^{\ast }<\max ({\it\Omega}^{\ast },N^{\ast })$), the presence of conical internal shear layers is observed in which the spatial structures of the harmonic response and of the mean flow correction are provided. At the point of focus of these internal shear layers on the rotation axis, the largest amplitudes are obtained: the angular velocity of the harmonic response and the mean flow correction are found to be $O({\it\varepsilon}E^{-1/3})$ and $({\it\varepsilon}^{2}E^{-2/3})$ respectively, where ${\it\varepsilon}$ is the libration amplitude and $E={\it\nu}^{\ast }/({\it\Omega}^{\ast }a^{\ast 2})$ is the Ekman number. We show that the solution in the internal shear layers and in the focus region is at leading order the same as that generated by an oscillating source of axial flow localized at the edge of the disk (oscillating Dirac ring source).

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37

Alonso, J. A., C. Hidalgo, M. A. Pedrosa, B. Van Milligen, D. Carralero e C. Silva. "Dynamic transport regulation by zonal flow-like structures in the TJ-II stellarator". Nuclear Fusion 52, n. 6 (24 aprile 2012): 063010. http://dx.doi.org/10.1088/0029-5515/52/6/063010.

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38

Kaladze, T. D., D. J. Wu, L. V. Tsamalashvili e G. V. Jandieri. "Localized magnetized Rossby structures under zonal shear flow in the ionospheric E-layer". Physics Letters A 365, n. 1-2 (maggio 2007): 140–43. http://dx.doi.org/10.1016/j.physleta.2007.01.002.

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39

Bottino, A., M. V. Falessi, T. Hayward-Schneider, A. Biancalani, S. Briguglio, R. Hatzky, Ph Lauber et al. "Time evolution and finite element representation of Phase Space Zonal Structures in ORB5". Journal of Physics: Conference Series 2397, n. 1 (1 dicembre 2022): 012019. http://dx.doi.org/10.1088/1742-6596/2397/1/012019.

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Abstract Phase Space Zonal Structures (PSZSs), obtained by averaging out dependencies on angle-like variables in the energetic particle (EP) distribution function, play a fundamental role in regulating EP transport induced by Alfvén instabilities in burning plasmas, acting as a slowly varying nonlinear equilibrium state. Therefore, they are of great interest for the development of reduced models for the description of EP heat and particle transport on long time scales, comparable with the energy confinement time, for future burning plasma experiments. In this work, we propose an efficient finite element based projection of the time evolution of the PSZS, suited for global particle-in-cell (PIC) gyrokinetic (GK) codes. The resulting algorithm has been implemented in the global GK PIC code ORB5. PSZSs can not only be used for validating reduced models, but also as a diagnostic tool for characterizing the nonlinear interaction in phase space between Alfvén instabilities and EPs in global GK simulations.

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40

Martinis, Carlos, Dustin Hickey, Joei Wroten, Jeffrey Baumgardner, Rebecca Macinnis, Caity Sullivan e Santiago Padilla. "All-Sky Imager Observations of the Latitudinal Extent and Zonal Motion of Magnetically Conjugate 630.0 nm Airglow Depletions". Atmosphere 11, n. 6 (16 giugno 2020): 642. http://dx.doi.org/10.3390/atmos11060642.

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630.0 nm all-sky imaging data are used to detect airglow depletions associated with equatorial spread F. Pairs of imagers located at geomagnetically conjugate locations in the American sector at low and mid-latitudes provide information on the occurrence rate and zonal motion of airglow depletions. Airglow depletions are seen extending to magnetic latitudes as high as 25°. An asymmetric extension is observed with structures in the northern hemisphere reaching higher latitudes. By tracking the zonal motion of airglow depletions, zonal plasma drifts in the thermosphere can be inferred and their simultaneous behavior in both hemispheres investigated. Case studies using El Leoncito and Mercedes imagers in the southern hemisphere, and the respective magnetically conjugate imagers at Villa de Leyva and Arecibo, provide consistent evidence of the influence of the South Atlantic Magnetic Anomaly on the dynamics and characteristics of the thermosphere–ionosphere system at low and mid-latitudes.

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41

KANE, R. P. "Long-term variations in the characteristics of the equatorial stratospheric zonal winds". MAUSAM 52, n. 3 (11 gennaio 2022): 515–26. http://dx.doi.org/10.54302/mausam.v52i3.1721.

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Stratospheric equatorial zonal winds from 1951 onwards up to the present show considerable long-term variations, more so at higher levels, These are rarely monotonic and often show multi-periodic structures, including a sunspot cycle (II year variations), Stratospheric temperatures and geopotential heights also show multi-periodic variations, A periodicity near 20 years is encountered often.

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42

Cravatte, S., Elodie Kestenare, Frédéric Marin, Pierre Dutrieux e Eric Firing. "Subthermocline and Intermediate Zonal Currents in the Tropical Pacific Ocean: Paths and Vertical Structure". Journal of Physical Oceanography 47, n. 9 (settembre 2017): 2305–24. http://dx.doi.org/10.1175/jpo-d-17-0043.1.

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AbstractThe mean subthermocline and intermediate zonal circulation in the tropical Pacific is investigated using a compilation of shipboard ADCP measurements and absolute geostrophic velocities constructed from a high-resolution 0–2000-m Argo climatology referenced to a 1000-m velocity field derived from Argo float drifts. This reference field is dominated by basinwide alternating zonal jets with a meridional wavelength of about 3°. In regions where the sampling of SADCP data is sufficient, the consistency between the two independent datasets is striking; using the Argo drift reference is crucial to capture the current structures. Two apparently distinct systems of alternating westward and eastward zonal jets are seen in both datasets equatorward of 10°: a series of low-latitude subthermocline currents (LLSCs) below the thermocline, extending from about 200 to 800 m, including the eastward Tsuchiya jets; and a series of low-latitude intermediate currents (LLICs), extending from about 700 to at least 2000 m. These systems seem to merge poleward of 10°. Both series shoal to lighter densities eastward. The subthermocline currents and their associated potential vorticity structures undergo a major shift near 155°W, suggesting some difference in the dynamic regime between the regions west and east of this longitude. Differing behaviors (the LLSCs tend to angle poleward to the east, whereas the LLICs angle slightly equatorward) suggest that these jets may be dynamically distinct, with different forcing mechanisms.

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43

Novikov, D. A., Ya V. Fomina, I. I. Yurchik, A. V. Chernykh, F. F. Dultsev e S. V. Golovin. "Optimal Set of Criteria for the Zonal Forecast of the Potential for Carbon Dioxide Capture and Storage in Geological Formations". Ecology and Industry of Russia 27, n. 4 (11 aprile 2023): 44–49. http://dx.doi.org/10.18412/1816-0395-2023-4-44-49.

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Geological criteria for the zonal evaluation of the RF territory potential for CO2 capture and storage are substantiated. The criteria of zonal forecast for the areas within the RF boundaries are proposed to arrange and monitor underground storage facilities are proposed on the basis of the international and Russian regulatory frameworks on the disposal of carbon dioxide, industrial wastewaters, toxic wastes, arrangement and monitoring of underground storage facilities for the purpose of implementing Carbon Capture and Storage (CCS) projects. The scheme of investigation of the geological structures is built up, and brief characterization of each parameter along with its significance degree in the evaluation system is presented.

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44

Punge, H. J., e M. A. Giorgetta. "Differences between the QBO in the first and in the second half of the ERA-40 reanalysis". Atmospheric Chemistry and Physics 7, n. 3 (7 febbraio 2007): 599–608. http://dx.doi.org/10.5194/acp-7-599-2007.

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Abstract. The representation of the quasi-biennial oscillation (QBO) is investigated in the ERA-40 reanalysis. In the lower stratosphere, where there are a reasonable number of observations, the representation of the QBO is equally good throughout the record. However, strong differences between the first and the second half of the zonal wind data set are found in the upper stratosphere, with a typical offset of –10 m/s in the equatorial zonal wind in the earlier part versus the later part of the ERA-40 record. At the same time, the strength of the QBO is similar. The 7-year running means of zonal wind, wind shear and temperature reveal interesting structures with major changes occuring in the beginning and the middle of the 1980s. Possible explanations are discussed. The identified change of the reanalysed wind profiles over time in ERA-40 demands for a careful use of equatorial upper stratospheric winds from the reanalysis e.g.~for model validation purposes.

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45

Dietrich, Wieland, Paula Wulff, Johannes Wicht e Ulrich R. Christensen. "Linking zonal winds and gravity – II. Explaining the equatorially antisymmetric gravity moments of Jupiter". Monthly Notices of the Royal Astronomical Society 505, n. 3 (2 giugno 2021): 3177–91. http://dx.doi.org/10.1093/mnras/stab1566.

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ABSTRACT The recent gravity field measurements of Jupiter (Juno) and Saturn (Cassini) confirm the existence of deep zonal flows reaching to a depth of 5 per cent and 15 per cent of the respective radius. Relating the zonal wind-induced density perturbations to the gravity moments has become a major tool to characterize the interior dynamics of gas giants. Previous studies differ with respect to the assumptions made on how the wind velocity relates to density anomalies, on the functional form of its decay with depth, and on the continuity of antisymmetric winds across the equatorial plane. For the case of Jupiter, most of the suggested vertical structures exhibit a rather smooth radial decay of the zonal wind, which seems at odds with the observed secular variation of the magnetic field and the prevailing barotropy of the zonal winds. Moreover, the results relied on modifications of the surface zonal flows, an artificial equatorial regularization or ignored the equatorial discontinuity altogether. We favour an alternative structure, where the equatorially antisymmetric zonal wind in an equatorial latitude belt between ±21° remains so shallow that it does not contribute to the gravity signal. The winds at higher latitudes suffice to convincingly explain the measured gravity moments. Our results indicate that the winds are barotropic, i.e. constant along cylinders, in the outer $3000$ km and decay rapidly below. The preferred wind structure is 50 per cent deeper than previously thought, agrees with the measured odd gravity moments, is compliant with the requirement of an adiabatic atmosphere and unbiased by the treatment of the equatorial discontinuity. We discuss possible implications for the interpretation of the secular variation of Jupiter’s magnetic field.

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46

L’Heureux, Michelle L., e David W. J. Thompson. "Observed Relationships between the El Niño–Southern Oscillation and the Extratropical Zonal-Mean Circulation". Journal of Climate 19, n. 2 (15 gennaio 2006): 276–87. http://dx.doi.org/10.1175/jcli3617.1.

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Abstract There is increasing evidence indicating that the climate response to variations in the El Niño–Southern Oscillation (ENSO) includes not only thermally forced zonal wind anomalies in the subtropics but also eddy-driven zonal wind anomalies that extend into the mid–high latitudes of both hemispheres. In this study, new insights into the observed seasonally varying signature of ENSO in the extratropical zonal-mean circulation are provided and the associated linkages with the dominant patterns of extratropical variability are examined. The zonal-mean extratropical atmospheric response to ENSO is characterized by two principal features: an equivalent barotropic dipole in the Southern Hemisphere (SH) zonal-mean zonal flow with centers of action located near ∼40° and ∼60° during austral summer, and a weaker, but analogous, dipole in the Northern Hemisphere (NH) with centers of action located near ∼25° and ∼45° during early and late boreal winter. Both structures are accompanied by eddy momentum flux anomalies that exhibit a remarkable degree of hemispheric symmetry. In the SH, the extratropical signature of ENSO projects strongly onto the primary mode of large-scale variability, the southern annular mode (SAM). During the austral summer, roughly 25% of the temporal variability in the SAM is linearly related to fluctuations in the ENSO cycle. An analogous relationship is not observed in association with the principal mode of climate variability in the NH, the northern annular mode (NAM). It is argued that the seasonally varying impact of ENSO on the extratropical circulation is consistent with the impact of the thermally forced subtropical wind anomalies on the dissipation of equatorward-propagating wave activity at subtropical latitudes.

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47

Sun, Cheng, e Jianping Li. "Space–Time Spectral Analysis of the Southern Hemisphere Daily 500-hPa Geopotential Height". Monthly Weather Review 140, n. 12 (1 dicembre 2012): 3844–56. http://dx.doi.org/10.1175/mwr-d-12-00019.1.

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Abstract In this paper the authors use the NCEP–Department of Energy (DOE) Reanalysis 2 (NCEP2) data from 1979 to 2004 to expand the daily 500-hPa geopotential height in the Southern Hemisphere (SH, 90°–20°S) into a double Fourier series, and analyze the temporal frequency characteristics of the expansion coefficients over various spatial scales. For the daily series over the whole year, the coefficient series of the extratropical-mean height is characterized by a significant low-frequency (10–30 day) variation. For zonal waves with (k, l) = (1–5, 1), where k and l are the zonal and meridional wavenumbers, respectively, the low-frequency variability is most pronounced for zonal wavenumbers 3 and 4; while the short wave with zonal wavenumber 5 has significant high-frequency (4–8 day) variability. For meridional waves with (k, l) = (0, 2–6), the meridional dipole (l = 2) makes a major contribution to the low-frequency variability, consistent with the intraseasonal space–time features of the southern annular mode (SAM). The meridional tripole (l = 3) also exhibits low-frequency variability. For two-dimensional waves (k, l) = (1–5, 2–6), the dipole is a preferred meridional structure for intraseasonal modes with large zonal scales, indicating an out-of-phase relationship between low-frequency planetary-scale waves at mid- and high latitudes. The diagnostic results outlined above can be explained, to a certain extent, by the dispersion relation for Rossby waves. Theoretical analysis indicates that zonal wavenumber 3, zonally symmetric flow such as SAM, and planetary-scale waves with meridional dipole structures may be interpreted as low-frequency eigenmodes of the atmosphere.

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Merzlyakov, E. G., e Ch Jacobi. "Quasi-two-day wave in an unstable summer atmosphere - some numerical results on excitation and propagation". Annales Geophysicae 22, n. 6 (14 giugno 2004): 1917–29. http://dx.doi.org/10.5194/angeo-22-1917-2004.

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Abstract. Based on numerical calculations we demonstrate that small changes in the smooth climatological background atmosphere may lead to an unstable mean zonal wind distribution in the summer middle atmosphere. We relate these changes to small ones because locations and power of the main circulation structures are conserved, except for the acceleration of the easterly jet in the stratosphere/mesosphere. The instability forces oscillations propagating westward with a period of about 2 days and zonal wave numbers s=3 and/or 4. There are variations in the mean zonal wind distribution due to the excitation and transient propagation of these waves, and the numerical results correspond to features of these variations observed in experimental studies. The growing waves tend to remove the source of excitation. This process is effective enough to reduce the strong easterly jet and to remove the strong negative gradient of the zonal mean potential vorticity in the region of the instability. Therefore, when these parameters are calculated as mean values over a long time interval, the obtained values are too small to provide the instability. Strong 2-day waves, in turn, are unstable and can generate secondary waves with longer periods and lower zonal wave numbers. This effect is only significant for extremely strong 2-day waves. Another process is found to be more effective to produce secondary waves. We demonstrated that the 2-day wave with s=3 forced by nonlinear interaction between the 10-14 day planetary waves and the 2-day wave of zonal wave number 4 is unstable. This wave instability generates secondary waves with amplitudes that are large enough to be observed by ground-based radars, for example.

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49

Tur, A. V., A. V. Chechkin e V. V. Yanovsky. "Negative viscosity and generation of dissipative solitons and zonal dissipative structures by drift waves". Physics of Fluids B: Plasma Physics 4, n. 11 (novembre 1992): 3513–23. http://dx.doi.org/10.1063/1.860359.

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Alonso, J. A., J. L. Velasco, J. Arévalo, C. Hidalgo, M. A. Pedrosa, B. Ph Van Milligen, D. Carralero e C. Silva. "Dynamics of zonal-flow-like structures in the edge of the TJ-II stellarator". Plasma Physics and Controlled Fusion 55, n. 1 (17 dicembre 2012): 014001. http://dx.doi.org/10.1088/0741-3335/55/1/014001.

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