Artykuły w czasopismach: „Quasigeostrophic”

1

Egger, Joseph. "Mountain torques in quasigeostrophic theory". Meteorologische Zeitschrift 12, nr 6 (1.12.2003): 301–4. http://dx.doi.org/10.1127/0941-2948/2003/0012-0301.

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2

Miyazaki, Takeshi, Koki Ueno i Tomoyuki Shimonishi. "Quasigeostrophic, Tilted Spheroidal Vortices". Journal of the Physical Society of Japan 68, nr 8 (15.08.1999): 2592–601. http://dx.doi.org/10.1143/jpsj.68.2592.

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3

Miyazaki, Takeshi, Masahiro Shimada i Naoya Takahashi. "Quasigeostrophic Wire-Vortex Model". Journal of the Physical Society of Japan 69, nr 10 (15.10.2000): 3233–43. http://dx.doi.org/10.1143/jpsj.69.3233.

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4

Miyazaki, Takeshi, Takahiro Fujiwara i Masahiro Yamamoto. "Quasigeostrophic Confocal Spheroidal Vortices". Journal of the Physical Society of Japan 72, nr 11 (15.11.2003): 2786–803. http://dx.doi.org/10.1143/jpsj.72.2786.

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5

Miyazaki, Takeshi, Yu Furuichi i Naoya Takahashi. "Quasigeostrophic Ellipsoidal Vortex Model". Journal of the Physical Society of Japan 70, nr 7 (15.07.2001): 1942–53. http://dx.doi.org/10.1143/jpsj.70.1942.

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6

Duan, Jinqiao, i Beniamin Goldys. "Ergodicity of stochastically forced large scale geophysical flows". International Journal of Mathematics and Mathematical Sciences 28, nr 6 (2001): 313–20. http://dx.doi.org/10.1155/s0161171201012443.

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We investigate the ergodicity of 2D large scale quasigeostrophic flows under random wind forcing. We show that the quasigeostrophic flows are ergodic under suitable conditions on the random forcing and on the fluid domain, and under no restrictions on viscosity, Ekman constant or Coriolis parameter. When these conditions are satisfied, then for any observable of the quasigeostrophic flows, its time average approximates the statistical ensemble average, as long as the time interval is sufficiently long.

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7

Delsole, Timothy. "Stochastic Models of Quasigeostrophic Turbulence". Surveys in Geophysics 25, nr 2 (marzec 2004): 107–49. http://dx.doi.org/10.1023/b:geop.0000028164.58516.b2.

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8

Juckes, Martin. "Quasigeostrophic Dynamics of the Tropopause". Journal of the Atmospheric Sciences 51, nr 19 (październik 1994): 2756–68. http://dx.doi.org/10.1175/1520-0469(1994)051<2756:qdott>2.0.co;2.

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9

Carton, Xavier. "Instability of Surface Quasigeostrophic Vortices". Journal of the Atmospheric Sciences 66, nr 4 (1.04.2009): 1051–62. http://dx.doi.org/10.1175/2008jas2872.1.

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Abstract The instability of circular vortices is studied numerically in the surface quasigeostrophic (SQG) model, and their evolutions are compared with those of barotropically unstable 2D vortices. The growth rates in the SQG model evidence similarity with their barotropic counterparts for moderate radial gradients of temperature (or of vorticity in the 2D model). For stronger gradients, SQG vortices are more unstable than 2D vortices. The nonlinear, finite-amplitude evolutions of perturbed vortices provide evidence that moderately unstable, elliptically perturbed vortices form tripoles. When they are more unstable, they break into two dipoles. Weakly unstable vortices with triangular perturbations form transient quadrupoles that break; they stabilize only for large gradients of mean temperature. Finally, with square perturbations, pentapoles degenerate into dipoles, at least for the range of mean temperature gradients explored here. The analysis of nonlinear stabilizations reveals that the deformation of the vortex core and the leak of its temperature anomaly to the periphery are essential ingredients to stabilize the perturbation at finite amplitude. In conclusion, SQG vortex instability exhibits considerable similarity to the barotropic instability of 2D vortices.

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10

Zhmur, V. V., i K. K. Pankratov. "Dynamics of desingularized quasigeostrophic vortices". Physics of Fluids A: Fluid Dynamics 3, nr 5 (maj 1991): 1464. http://dx.doi.org/10.1063/1.857998.

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11

DelSole, Timothy. "Optimal Perturbations in Quasigeostrophic Turbulence". Journal of the Atmospheric Sciences 64, nr 4 (1.04.2007): 1350–64. http://dx.doi.org/10.1175/jas3875.1.

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Abstract This paper tests the hypothesis that optimal perturbations in quasigeostrophic turbulence are excited sufficiently strongly and frequently to account for the energy-containing eddies. Optimal perturbations are defined here as singular vectors of the propagator, for the energy norm, corresponding to the equations of motion linearized about the time-mean flow. The initial conditions are drawn from a numerical solution of the nonlinear equations associated with the linear propagator. Experiments confirm that energy is concentrated in the leading evolved singular vectors, and that the average energy in the initial singular vectors is within an order of magnitude of that required to explain the average energy in the evolved singular vectors. Furthermore, only a small number of evolved singular vectors (4 out of 4000) are needed to explain the dominant eddy structure when total energy exceeds a predefined threshold. The initial singular vectors explain only 10% of such events, but this discrepancy was similar to that of the full propagator, suggesting that it arises primarily due to errors in the propagator. In the limit of short lead times, energy conservation can be expressed in terms of suitable singular vectors to constrain the energy distribution of the singular vectors in statistically steady equilibrium. This and other connections between linear optimals and nonlinear dynamics suggests that the positive results found here should carry over to other systems, provided the propagator and initial states are chosen consistently with respect to the nonlinear system.

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12

Holm, Darryl D., i Vladimir Zeitlin. "Hamilton’s principle for quasigeostrophic motion". Physics of Fluids 10, nr 4 (kwiecień 1998): 800–806. http://dx.doi.org/10.1063/1.869623.

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13

Grooms, Ian, i Andrew J. Majda. "Stochastic superparameterization in quasigeostrophic turbulence". Journal of Computational Physics 271 (sierpień 2014): 78–98. http://dx.doi.org/10.1016/j.jcp.2013.09.020.

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14

Gavrilov, Milivoj B., i Ivana A. Tošić. "Dispersion Characteristics of Discrete Quasigeostrophic Modes". Monthly Weather Review 127, nr 9 (wrzesień 1999): 2197–203. http://dx.doi.org/10.1175/1520-0493(1999)127<2197:dcodqm>2.0.co;2.

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15

Nycander, J. "Drift Velocity of Radiating Quasigeostrophic Vortices". Journal of Physical Oceanography 31, nr 8 (sierpień 2001): 2178–85. http://dx.doi.org/10.1175/1520-0485(2001)031<2178:dvorqv>2.0.co;2.

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16

Jamaloodeen, Mohamed I., i Paul K. Newton. "Two-layer quasigeostrophic potential vorticity model". Journal of Mathematical Physics 48, nr 6 (czerwiec 2007): 065601. http://dx.doi.org/10.1063/1.2469221.

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17

Berrisford, P., J. C. Marshall i A. A. White. "Quasigeostrophic Potential Vorticity in Isentropic Coordinates". Journal of the Atmospheric Sciences 50, nr 5 (marzec 1993): 778–82. http://dx.doi.org/10.1175/1520-0469(1993)050<0778:qpviic>2.0.co;2.

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18

DelSole, Timothy. "Can Quasigeostrophic Turbulence Be Modeled Stochastically?" Journal of the Atmospheric Sciences 53, nr 11 (czerwiec 1996): 1617–33. http://dx.doi.org/10.1175/1520-0469(1996)053<1617:cqtbms>2.0.co;2.

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19

Rotunno, Richard, David J. Muraki i Chris Snyder. "Unstable Baroclinic Waves beyond Quasigeostrophic Theory". Journal of the Atmospheric Sciences 57, nr 19 (październik 2000): 3285–95. http://dx.doi.org/10.1175/1520-0469(2000)057<3285:ubwbqt>2.0.co;2.

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20

Asselin, Olivier, Peter Bartello i David N. Straub. "On quasigeostrophic dynamics near the tropopause". Physics of Fluids 28, nr 2 (luty 2016): 026601. http://dx.doi.org/10.1063/1.4941761.

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21

Hendershott, Myrl C. "The ventilated thermocline in quasigeostrophic approximation". Journal of Marine Research 47, nr 1 (1.02.1989): 33–53. http://dx.doi.org/10.1357/002224089785076398.

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22

Álvarez, Alberto, Emilio Hernández-García i Joaquín Tintoré. "Noise rectification in quasigeostrophic forced turbulence". Physical Review E 58, nr 6 (1.12.1998): 7279–82. http://dx.doi.org/10.1103/physreve.58.7279.

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23

Muraki, David J., i Chris Snyder. "Vortex Dipoles for Surface Quasigeostrophic Models". Journal of the Atmospheric Sciences 64, nr 8 (sierpień 2007): 2961–67. http://dx.doi.org/10.1175/jas3958.1.

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A new class of exact vortex dipole solutions is derived for surface quasigeostrophic (sQG) models. The solutions extend the two-dimensional barotropic modon to fully three-dimensional, continuously stratified flow and are a simple model of localized jets on the tropopause. In addition to the basic sQG dipole, dipole structures exist for a layer of uniform potential vorticity between two rigid boundaries and for a dipole in the presence of uniform background vertical shear and horizontal potential temperature gradient. In the former case, the solution approaches the barotropic Lamb dipole in the limit of a layer that is shallow relative to the Rossby depth based on the dipole’s radius. In the latter case, dipoles that are bounded in the far field must propagate counter to the phase speed of the linear edge waves associated with the surface temperature gradient.

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24

Miyazaki, Takeshi, Masahiro Yamamoto i Shinsuke Fujishima. "Counter-Rotating Quasigeostrophic Ellipsoidal Vortex Pair". Journal of the Physical Society of Japan 72, nr 8 (15.08.2003): 1948–62. http://dx.doi.org/10.1143/jpsj.72.1948.

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25

Duan, Jinqiao, Darryl D. Holm i Kaitai Li. "Variational methods and nonlinear quasigeostrophic waves". Physics of Fluids 11, nr 4 (kwiecień 1999): 875–79. http://dx.doi.org/10.1063/1.869959.

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26

Pinardi, Nadia, i Allan R. Robinson. "Quasigeostrophic energetics of open ocean regions". Dynamics of Atmospheres and Oceans 10, nr 3 (grudzień 1986): 185–219. http://dx.doi.org/10.1016/0377-0265(86)90013-8.

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27

McDonald, N. Robb. "A new translating quasigeostrophic V-state". European Journal of Mechanics - B/Fluids 23, nr 4 (lipiec 2004): 633–44. http://dx.doi.org/10.1016/j.euromechflu.2003.10.004.

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28

Schneider, Tapio. "Zonal Momentum Balance, Potential Vorticity Dynamics, and Mass Fluxes on Near-Surface Isentropes". Journal of the Atmospheric Sciences 62, nr 6 (1.06.2005): 1884–900. http://dx.doi.org/10.1175/jas3341.1.

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Abstract While it has been recognized for some time that isentropic coordinates provide a convenient framework for theories of the global circulation of the atmosphere, the role of boundary effects in the zonal momentum balance and in potential vorticity dynamics on isentropes that intersect the surface has remained unclear. Here, a balance equation is derived that describes the temporal and zonal mean balance of zonal momentum and of potential vorticity on isentropes, including the near-surface isentropes that sometimes intersect the surface. Integrated vertically, the mean zonal momentum or potential vorticity balance leads to a balance condition that relates the mean meridional mass flux along isentropes to eddy fluxes of potential vorticity and surface potential temperature. The isentropic-coordinate balance condition formally resembles balance conditions well known in quasigeostrophic theory, but on near-surface isentropes it generally differs from the quasigeostrophic balance conditions. Not taking the intersection of isentropes with the surface into account, quasigeostrophic theory does not adequately represent the potential vorticity dynamics and mass fluxes on near-surface isentropes—a shortcoming that calls into question the relevance of quasigeostrophic theories for the macroturbulence and global circulation of the atmosphere.

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29

Nielsen-Gammon, John W., i David A. Gold. "Dynamical Diagnosis: A Comparison of Quasigeostrophy and Ertel Potential Vorticity". Meteorological Monographs 55 (1.11.2008): 183–202. http://dx.doi.org/10.1175/0065-9401-33.55.183.

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Abstract Advances in computer power, new forecasting challenges, and new diagnostic techniques have brought about changes in the way atmospheric development and vertical motion are diagnosed in an operational setting. Many of these changes, such as improved model skill, model resolution, and ensemble forecasting, have arguably been detrimental to the ability of forecasters to understand and respond to the evolving atmosphere. The use of nondivergent wind in place of geostrophic wind would be a step in the right direction, but the advantages of potential vorticity suggest that its widespread adoption as a diagnostic tool on the west side of the Atlantic is overdue. Ertel potential vorticity (PV), when scaled to be compatible with pseudopotential vorticity, is generally similar to pseudopotential vorticity, so forecasters accustomed to quasigeostrophic reasoning through the height tendency equation can transfer some of their intuition into the Ertel-PV framework. Indeed, many of the differences between pseudopotential vorticity and Ertel potential vorticity are consequences of the choice of definition of quasigeostrophic PV and are not fundamental to the quasigeostrophic system. Thus, at its core, PV thinking is consistent with commonly used quasigeostrophic diagnostic techniques.

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30

Brüggemann, Nils, i Carsten Eden. "Routes to Dissipation under Different Dynamical Conditions". Journal of Physical Oceanography 45, nr 8 (sierpień 2015): 2149–68. http://dx.doi.org/10.1175/jpo-d-14-0205.1.

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AbstractIn this study, it is investigated how ageostrophic dynamics generate an energy flux toward smaller scales. Numerical simulations of baroclinic instability are used with varying dynamical conditions ranging from quasigeostrophic balance to ageostrophic flows. It turns out that dissipation at smaller scales by viscous friction is much more efficient if the flow is dominated by ageostrophic dynamics than in quasigeostrophic conditions. In the presence of ageostrophic dynamics, an energy flux toward smaller scales is observed while energy is transferred toward larger scales for quasigeostrophic dynamics. Decomposing the velocity field into its rotational and divergent components shows that only the divergent velocity component, which becomes stronger for ageostrophic flows, features a downscale flux. Variation of the dynamical conditions from ageostrophic dynamics to quasigeostrophic balanced flows shows that the forward energy flux and therefore the small-scale dissipation decreases as soon as the horizontal divergent velocity component decreases. A functional relationship between the small-scale dissipation and the local Richardson number is estimated. This functional relationship is used to obtain a global estimate of the small-scale dissipation of 0.31 ± 0.23 TW from a high-resolution realistic global ocean model. This emphasizes that an ageostrophic direct route to dissipation might be of importance in the ocean energy cycle.

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31

Pratt, Lawrence J., M. Susan Lozier i Natalia Beliakova. "Parcel Trajectories in Quasigeostrophic Jets: Neutral Modes". Journal of Physical Oceanography 25, nr 6 (czerwiec 1995): 1451–66. http://dx.doi.org/10.1175/1520-0485(1995)025<1451:ptiqjn>2.0.co;2.

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32

Müller, Peter. "Coherence Maps for Wind-Forced Quasigeostrophic Flows*". Journal of Physical Oceanography 27, nr 9 (wrzesień 1997): 1927–36. http://dx.doi.org/10.1175/1520-0485(1997)027<1927:cmfwfq>2.0.co;2.

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33

Berloff, Pavel S., i James C. McWilliams. "Quasigeostrophic Dynamics of the Western Boundary Current". Journal of Physical Oceanography 29, nr 10 (październik 1999): 2607–34. http://dx.doi.org/10.1175/1520-0485(1999)029<2607:qdotwb>2.0.co;2.

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34

da Silveira, Ilson C. A., i Glenn R. Flierl. "Eddy Formation in 2½-Layer, Quasigeostrophic Jets". Journal of Physical Oceanography 32, nr 3 (marzec 2002): 729–45. http://dx.doi.org/10.1175/1520-0485(2002)032<0729:efilqj>2.0.co;2.

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35

Muraki, David J., Chris Snyder i Richard Rotunno. "The Next-Order Corrections to Quasigeostrophic Theory". Journal of the Atmospheric Sciences 56, nr 11 (czerwiec 1999): 1547–60. http://dx.doi.org/10.1175/1520-0469(1999)056<1547:tnoctq>2.0.co;2.

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36

Vizman, Cornelia. "Cocycles and stream functions in quasigeostrophic motion". Journal of Nonlinear Mathematical Physics 15, nr 2 (styczeń 2008): 140–46. http://dx.doi.org/10.2991/jnmp.2008.15.2.1.

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37

Kalashnik, M. V., M. V. Kurgansky i S. V. Kostrykin. "Instability of Surface Quasigeostrophic Spatially Periodic Flows". Journal of the Atmospheric Sciences 77, nr 1 (16.12.2019): 239–55. http://dx.doi.org/10.1175/jas-d-19-0100.1.

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

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38

Laîné, Alexandre, Guillaume Lapeyre i Gwendal Rivière. "A Quasigeostrophic Model for Moist Storm Tracks". Journal of the Atmospheric Sciences 68, nr 6 (1.06.2011): 1306–22. http://dx.doi.org/10.1175/2011jas3618.1.

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Abstract The effect of moisture and latent heat release is investigated in the context of a three-level quasigeostrophic model on the sphere. The model is based on an existing dry model that was shown to be able to reproduce the midlatitude synoptic and low-frequency variability of the troposphere. In addition to potential vorticity equations, moisture evolution equations are included with a simple precipitation scheme. The model can be forced using reanalysis datasets to represent the observed climatology. After the description of the model, the Northern Hemisphere midlatitude climatic characteristics of the moist model are compared to its dry counterpart and to the 40-yr ECMWF Re-Analysis (ERA-40). The jet of the moist model is weakened in its central and northern part and enhanced in its southern part compared to the dry version, which generally decreases the model biases compared to reanalyses. Latent heating processes are mainly responsible for the global decrease in westerlies in the jet-core regions. Precipitation mainly occurs slightly poleward of the jet axes, thereby reducing the meridional temperature gradient and the wind through thermal wind balance. The mean synoptic activity is reduced according to the decrease in baroclinicity, as well as the mean low-frequency variability. A diagnosis of synoptic wave breaking is performed and the characteristics of the moist model are closer to the ones found in reanalyses, especially with more occurrence of cyclonic wave breaking. Weather regimes are slightly better represented in the moist model, although changes are weak compared to the intrinsic model biases. The behavior of the moist model around its climatology indicates that it could be used to run sensitivity experiments.

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39

Miyazaki, Takeshi, Akinori Asai, Masahiro Yamamoto i Shinsuke Fujishima. "Numerical Validation of Quasigeostrophic Ellipsoidal Vortex Model". Journal of the Physical Society of Japan 71, nr 11 (15.11.2002): 2687–99. http://dx.doi.org/10.1143/jpsj.71.2687.

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40

Mu, Mu. "Nonlinear stability of two-dimensional quasigeostrophic motions". Geophysical & Astrophysical Fluid Dynamics 65, nr 1-4 (lipiec 1992): 57–76. http://dx.doi.org/10.1080/03091929208225239.

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41

Plougonven, R., i J. Vanneste. "Quasigeostrophic Dynamics of a Finite-Thickness Tropopause". Journal of the Atmospheric Sciences 67, nr 10 (1.10.2010): 3149–63. http://dx.doi.org/10.1175/2010jas3502.1.

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Abstract A model of tropopause dynamics is derived that is of intermediate complexity between the three-dimensional quasigeostrophic model and the surface quasigeostrophic (SQG) model. The model assumes that a sharp transition in stratification occurs over a small but finite tropopause region separating regions of uniform potential vorticity (PV). The model is derived using a matched-asymptotics technique, with the ratio of the thickness of the tropopause region to the typical vertical scale of perturbations outside as a small parameter. It reduces to SQG to leading order in this parameter but takes into account the next-order correction. As a result it remains three-dimensional, although with a PV inversion relation that is greatly simplified compared to the Laplacian inversion of quasigeostrophic theory. The model is applied to examine the linear dynamics of perturbations at the tropopause. Edge waves, described in the SQG approximation, are recovered, and explicit expressions are obtained for the corrections to their frequency and structure that result from the finiteness of the tropopause region. The sensitivity of these corrections to the stratification and shear profiles across the tropopause is investigated. In addition, the evolution of perturbations with near-zero vertically integrated PV is discussed. These perturbations, which are filtered out by the SQG approximation, are represented by a continuous spectrum of singular modes and evolve as sheared disturbances. The decomposition of arbitrary perturbations into edge-wave and continuous-spectrum contributions is discussed.

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42

Storer, Benjamin A., Francis J. Poulin i Claire Ménesguen. "The Dynamics of Quasigeostrophic Lens-Shaped Vortices". Journal of Physical Oceanography 48, nr 4 (kwiecień 2018): 937–57. http://dx.doi.org/10.1175/jpo-d-17-0039.1.

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AbstractThe stability of lens-shaped vortices is revisited in the context of an idealized quasigeostrophic model. We compute the stability characteristics with higher accuracy and for a wider range of Burger numbers (Bu) than what was previously done. It is found that there are four distinct Bu regions of linear instability. Over the primary region of interest (0.1 < Bu < 10), we confirm that the first and second azimuthal modes are the only linearly unstable modes, and they are associated with vortex tilting and tearing, respectively. Moreover, the most unstable first azimuthal mode is not precisely captured by the linear stability analysis because of the extra condition that is imposed at the vortex center, and accurate calculations of the second azimuthal mode require higher resolution than was previously considered. We also study the nonlinear evolution of lens-shaped vortices in the context of this model and present the following results. First, vortices with a horizontal length scale a little less than the radius of deformation (Bu > 1) are barotropically unstable and develop a wobble, whereas those with a larger horizontal length scale (Bu < 1) are baroclinically unstable and often split. Second, the transfer of energy between different horizontal scales is quantified in two typical cases of barotropic and baroclinic instability. Third, after the instability the effective Bu is closer to unity.

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43

Watwood, Matthew, Ian Grooms, Keith A. Julien i K. Shafer Smith. "Energy-conserving Galerkin approximations for quasigeostrophic dynamics". Journal of Computational Physics 388 (lipiec 2019): 23–40. http://dx.doi.org/10.1016/j.jcp.2019.03.029.

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44

Meacham, S. P. "Quasigeostrophic, ellipsoidal vortices in a stratified fluid". Dynamics of Atmospheres and Oceans 16, nr 3-4 (styczeń 1992): 189–223. http://dx.doi.org/10.1016/0377-0265(92)90007-g.

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45

Walstad, Leonard J., i Allan R. Robinson. "A coupled surface boundary-layer-quasigeostrophic model". Dynamics of Atmospheres and Oceans 18, nr 3-4 (sierpień 1993): 151–207. http://dx.doi.org/10.1016/0377-0265(93)90009-v.

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46

Venaille, Antoine, Geoffrey K. Vallis i K. Shafer Smith. "Baroclinic Turbulence in the Ocean: Analysis with Primitive Equation and Quasigeostrophic Simulations". Journal of Physical Oceanography 41, nr 9 (1.09.2011): 1605–23. http://dx.doi.org/10.1175/jpo-d-10-05021.1.

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Abstract This paper examines the factors determining the distribution, length scale, magnitude, and structure of mesoscale oceanic eddies in an eddy-resolving primitive equation simulation of the Southern Ocean [Modeling Eddies in the Southern Ocean (MESO)]. In particular, the authors investigate the hypothesis that the primary source of mesoscale eddies is baroclinic instability acting locally on the mean state. Using local mean vertical profiles of shear and stratification from an eddying primitive equation simulation, the forced–dissipated quasigeostrophic equations are integrated in a doubly periodic domain at various locations. The scales, energy levels, and structure of the eddies found in the MESO simulation are compared to those predicted by linear stability analysis, as well as to the eddying structure of the quasigeostrophic simulations. This allows the authors to quantitatively estimate the role of local nonlinear effects and cascade phenomena in the generation of the eddy field. There is a modest transfer of energy (an “inverse cascade”) to larger scales in the horizontal, with the length scale of the resulting eddies typically comparable to or somewhat larger than the wavelength of the most unstable mode. The eddies are, however, manifestly nonlinear, and in many locations the turbulence is fairly well developed. Coherent structures also ubiquitously emerge during the nonlinear evolution of the eddy field. There is a near-universal tendency toward the production of grave vertical scales, with the barotropic and first baroclinic modes dominating almost everywhere, but there is a degree of surface intensification that is not captured by these modes. Although the results from the local quasigeostrophic model compare well with those of the primitive equation model in many locations, some profiles do not equilibrate in the quasigeostrophic model. In many cases, bottom friction plays an important quantitative role in determining the final scale and magnitude of eddies in the quasigeostrophic simulations.

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Harvey, Benjamin J., Maarten H. P. Ambaum i Xavier J. Carton. "Instability of Shielded Surface Temperature Vortices". Journal of the Atmospheric Sciences 68, nr 5 (1.05.2011): 964–71. http://dx.doi.org/10.1175/2010jas3669.1.

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Abstract The stability characteristics of the surface quasigeostrophic shielded Rankine vortex are found using a linearized contour dynamics model. Both the normal modes and nonmodal evolution of the system are analyzed and the results are compared with two previous studies. One is a numerical study of the instability of smooth surface quasigeostrophic vortices with which qualitative similarities are found and the other is a corresponding study for the two-dimensional Euler system with which several notable differences are highlighted.

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Egger, Joseph. "A modified quasigeostrophic equation for barotropic mean flow over topography". Meteorologische Zeitschrift 12, nr 1 (17.03.2003): 43–46. http://dx.doi.org/10.1127/0941-2948/2003/0012-0043.

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Zurita-Gotor, Pablo, i Geoffrey K. Vallis. "Equilibration of Baroclinic Turbulence in Primitive Equations and Quasigeostrophic Models". Journal of the Atmospheric Sciences 66, nr 4 (1.04.2009): 837–63. http://dx.doi.org/10.1175/2008jas2848.1.

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Abstract This paper investigates the equilibration of baroclinic turbulence in an idealized, primitive equation, two-level model, focusing on the relation with the phenomenology of quasigeostrophic turbulence theory. Simulations with a comparable two-layer quasigeostrophic model are presented for comparison, with the deformation radius in the quasigeostrophic model being set using the stratification from the primitive equation model. Over a fairly broad parameter range, the primitive equation and quasigeostrophic results are in qualitative and, to some degree, quantitative agreement and are consistent with the phenomenology of geostrophic turbulence. The scale, amplitude, and baroclinicity of the eddies and the degree of baroclinic instability of the mean flow all vary fairly smoothly with the imposed parameters; both models are able, in some parameter ranges, to produce supercritical flows. The criticality in the primitive equation model, which does not have any convective parameterization scheme, is fairly sensitive to the external parameters, most notably the planet size (i.e., the f /β ratio), the forcing time scale, and the factors influencing the stratification. In some parameter settings of the models, although not those that are most realistic for the earth’s atmosphere, it is possible to produce eddies that are considerably larger than the deformation scales and an inverse cascade in the barotropic flow with a −5/3 spectrum. The vertical flux of heat is found to be related to the isentropic slope.

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Abadias, Luciano, i Pedro J. Miana. "Quasigeostrophic Equations for Fractional Powers of Infinitesimal Generators". Journal of Function Spaces 2019 (7.02.2019): 1–7. http://dx.doi.org/10.1155/2019/4763450.

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In this paper we treat the following partial differential equation, the quasigeostrophic equation: ∂/∂t+u·∇f=-σ-Aαf, 0≤α≤1, where (A,D(A)) is the infinitesimal generator of a convolution C0-semigroup of positive kernel on Lp(Rn), with 1≤p<∞. Firstly, we give remarkable pointwise and integral inequalities involving the fractional powers (-A)α for 0≤α≤1. We use these estimates to obtain Lp-decayment of solutions of the above quasigeostrophic equation. These results extend the case of fractional derivatives (taking A=Δ, the Laplacian), which has been studied in the literature.

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