The Diffusive Approximation for Eddy Fluxes in Baroclinically Unstable Jets

1996 ◽  
Vol 53 (9) ◽  
pp. 1262-1272 ◽  
Author(s):  
Valentina Pavan ◽  
Isaac M. Held
Keyword(s):  
Diffusive Approximation ◽  
Eddy Fluxes

scholarly journals Medium induced QCD cascades: broadening and rescattering during branching

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
E. Blanco ◽  
K. Kutak ◽  
W. Płaczek ◽  
M. Rohrmoser ◽  
R. Straka
Keyword(s):  
Momentum Transfer ◽  
Quark Gluon Plasma ◽  
Evolution Equations ◽  
Gaussian Approximation ◽  
Gluon Plasma ◽  
Jet Quenching ◽  
Diffusive Approximation

Abstract We study evolution equations describing jet propagation through quark-gluon plasma (QGP). In particular we investigate the contribution of momentum transfer during branching and find that such a contribution is sizeable. Furthermore, we study various approximations, such as the Gaussian approximation and the diffusive approximation to the jet-broadening term. We notice that in order to reproduce the BDIM equation (without the momentum transfer in the branching) the diffusive approximation requires a very large value of the jet-quenching parameter $$ \hat{q} $$ q ̂ .

scholarly journals Eddy Phase Speeds in a Two-Layer Model of Quasigeostrophic Baroclinic Turbulence with Applications to Ocean Observations

2016 ◽  
Vol 46 (6) ◽  
pp. 1963-1985 ◽  
Author(s):  
Lei Wang ◽  
Malte Jansen ◽  
Ryan Abernathey
Keyword(s):  
Practical Importance ◽  
Phase Speed ◽  
Wave Theory ◽  
Inverse Cascade ◽  
Barotropic Mode ◽  
Eddy Fluxes ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Ocean Observations ◽  
Shed Light

AbstractThe phase speed spectrum of ocean mesoscale eddies is fundamental to understanding turbulent baroclinic flows. Since eddy phase propagation has been shown to modulate eddy fluxes, an understanding of eddy phase speeds is also of practical importance for the development of improved eddy parameterizations for coarse resolution ocean models. However, it is not totally clear whether and how linear Rossby wave theory can be used to explain the phase speed spectra in various weakly turbulent flow regimes. Using linear analysis, theoretical constraints are identified that control the eddy phase speed in a two-layer quasigeostrophic (QG) model. These constraints are then verified in a series of nonlinear two-layer QG simulations, spanning a range of parameters with potential relevance to the ocean. In the two-layer QG model, the strength of the inverse cascade exerts an important control on the eddy phase speed. If the inverse cascade is weak, the phase speed spectrum is reasonably well approximated by the phase speed of the linearly most unstable mode. A significant inverse cascade instead leads to barotropization, which in turn leads to mean phase speeds closer to those of barotropic-mode Rossby waves. The two-layer QG results are qualitatively consistent with the observed eddy phase speed spectra in the Antarctic Circumpolar Current and may also shed light on the interpretation of phase speed spectra observed in other regions.

Eddy fluxes and the biennial stratospheric oscillation

1966 ◽  
Vol 92 (394) ◽  
pp. 481-489 ◽  
Author(s):  
J. M. Wallace ◽  
R. E. Newell
Keyword(s):  
Eddy Fluxes

Parameterization of Eddy Fluxes near Oceanic Boundaries

2008 ◽  
Vol 21 (12) ◽  
pp. 2770-2789 ◽  
Author(s):  
Raffaele Ferrari ◽  
James C. McWilliams ◽  
Vittorio M. Canuto ◽  
Mikhail Dubovikov
Keyword(s):  
Boundary Layer ◽  
Transition Layer ◽  
General Circulation ◽  
Mesoscale Eddies ◽  
Turbulent Boundary Layers ◽  
Mesoscale Variability ◽  
Transition Layers ◽  
Boundary Layer Turbulence ◽  
Dynamical Coupling ◽  
Eddy Fluxes

Abstract In the stably stratified interior of the ocean, mesoscale eddies transport materials by quasi-adiabatic isopycnal stirring. Resolving or parameterizing these effects is important for modeling the oceanic general circulation and climate. Near the bottom and near the surface, however, microscale boundary layer turbulence overcomes the adiabatic, isopycnal constraints for the mesoscale transport. In this paper a formalism is presented for representing this transition from adiabatic, isopycnally oriented mesoscale fluxes in the interior to the diabatic, along-boundary mesoscale fluxes near the boundaries. A simple parameterization form is proposed that illustrates its consequences in an idealized flow. The transition is not confined to the turbulent boundary layers, but extends into the partially diabatic transition layers on their interiorward edge. A transition layer occurs because of the mesoscale variability in the boundary layer and the associated mesoscale–microscale dynamical coupling.

scholarly journals Integral Constraints for Momentum and Energy in Zonal Flows with Parameterized Potential Vorticity Fluxes: Governing Parameters

2014 ◽  
Vol 44 (3) ◽  
pp. 922-943 ◽  
Author(s):  
V. O. Ivchenko ◽  
S. Danilov ◽  
B. Sinha ◽  
J. Schröter
Keyword(s):  
Ocean Circulation ◽  
Potential Vorticity ◽  
Channel Model ◽  
Bottom Topography ◽  
Flat Bottom ◽  
Zonal Flows ◽  
Integral Constraints ◽  
Variable Bottom ◽  
Eddy Fluxes ◽  
The Impact

Abstract Integral constraints for momentum and energy impose restrictions on parameterizations of eddy potential vorticity (PV) fluxes. The impact of these constraints is studied for a wind-forced quasigeostrophic two-layer zonal channel model with variable bottom topography. The presence of a small parameter, given by the ratio of Rossby radius to the width of the channel, makes it possible to find an analytical/asymptotic solution for the zonally and time-averaged flow, given diffusive parameterizations for the eddy PV fluxes. This solution, when substituted in the constraints, leads to nontrivial explicit restrictions on diffusivities. The system is characterized by four dimensionless governing parameters with a clear physical interpretation. The bottom form stress, the major term balancing the external force of wind stress, depends on the governing parameters and fundamentally modifies the restrictions compared to the flat bottom case. While the analytical solution bears an illustrative character, it helps to see certain nontrivial connections in the system that will be useful in the analysis of more complicated models of ocean circulation. A numerical solution supports the analytical study and confirms that the presence of topography strongly modifies the eddy fluxes.

scholarly journals Towards a further understanding of the dynamics in the excitatory NNLIF neuron model: Blow-up and global existence

2021 ◽  
Vol 0 (0) ◽  
pp. 0
Author(s):  
Pierre Roux ◽  
Delphine Salort
Keyword(s):  
Global Existence ◽  
Blow Up ◽  
Mean Field ◽  
Classical Solutions ◽  
Field Limit ◽  
Mean Field Limit ◽  
Diffusive Approximation ◽  
The Mean ◽  
Weak Connectivity ◽  
Time Existence

<p style='text-indent:20px;'>The Nonlinear Noisy Leaky Integrate and Fire (NNLIF) model is widely used to describe the dynamics of neural networks after a diffusive approximation of the mean-field limit of a stochastic differential equation. In previous works, many qualitative results were obtained: global existence in the inhibitory case, finite-time blow-up in the excitatory case, convergence towards stationary states in the weak connectivity regime. In this article, we refine some of these results in order to foster the understanding of the model. We prove with deterministic tools that blow-up is systematic in highly connected excitatory networks. Then, we show that a relatively weak control on the firing rate suffices to obtain global-in-time existence of classical solutions.</p>

scholarly journals Diffusion-rotational parameterization of eddy fluxes of potential vorticity: barotropic flow in the zonal channel

2019 ◽  
Vol 55 (1) ◽  
pp. 3-16
Author(s):  
V. O. Ivchenko ◽  
V. B. Zalesny
Keyword(s):  
Analytical Solution ◽  
Potential Vorticity ◽  
Rotational Component ◽  
Flow Disturbances ◽  
Barotropic Flow ◽  
Eddy Fluxes ◽  
Potential Enstrophy

The problem of parametrization of the eddy fluxes of a potential vorticity is discussed. Traditional diffusion parameterization is complemented by the inclusion of a rotational component. For the analysis of the new scheme, a quasi-geostrophic model of the dynamics of the barotropic flow in a zonal channel with a non-uniform bottom is used. An analytical solution of the problem is found and the influence of topography on the flow disturbances is discussed. It is shown that the equation for the eddy potential enstrophy allows to relate diffusion and «rotational» coefficients.

New estimates for the heat flux across the Polar Front: spatial and temporal variability in recent years

2013 ◽  
Vol 25 (3) ◽  
pp. 433-444 ◽  
Author(s):  
João Marcos Azevedo Correia De Souza ◽  
Afonso De Moraes Paiva ◽  
Karina Von Schuckmann
Keyword(s):  
Heat Flux ◽  
Heat Balance ◽  
Polar Front ◽  
Spatial And Temporal Variability ◽  
Large Contribution ◽  
Direct Estimate ◽  
Atlantic Sector ◽  
Eddy Heat Flux ◽  
Temporal And Spatial Variability ◽  
Eddy Fluxes

AbstractTwo different methodologies are applied in order to quantify the eddy contribution to the heat flux across the Polar Front, between January 2006 and December 2009. First, the eddy fluxes are indirectly estimated through a heat balance based on geostrophic fluxes obtained from the Argo climatological temperature and salinity. Second, a parametric model based on sea level anomaly data from a merged satellite product is used to obtain a direct estimate of the eddy heat flux and its temporal and spatial variability. The results obtained through the heat balance (-80.5 ± 16.45 x 1013 W) and the parameterization (-56.2 ± 4.18 x 1013 W) are within the range established by previous studies. The eddy heat flux is observed to be concentrated in a few narrow regions, with a particularly large contribution from the Atlantic sector. A trend of intensification of the southward heat flux is observed in the study period (-0.44 x 1013 W year-1), compatible with recent modelling and observational studies.

scholarly journals Can Eddy Fluxes Serve as a Catalyst for Hurricane and Typhoon Formation?*

1998 ◽  
Vol 55 (12) ◽  
pp. 2201-2219 ◽  
Author(s):  
Malakondayya Challa ◽  
Richard L. Pfeffer ◽  
Qiang Zhao ◽  
Simon W. Chang
Keyword(s):  
Eddy Fluxes

scholarly journals Moisture transport in observations and reanalyses as a proxy for snow accumulation in East Antarctica

2019 ◽  
Vol 13 (2) ◽  
pp. 413-425 ◽  
Author(s):  
Ambroise Dufour ◽  
Claudine Charrondière ◽  
Olga Zolina
Keyword(s):  
Moisture Transport ◽  
Precipitable Water ◽  
Daily Basis ◽  
Snow Accumulation ◽  
East Antarctica ◽  
Moisture Convergence ◽  
Sea Level Changes ◽  
Moisture Fluxes ◽  
Eddy Fluxes

Abstract. Atmospheric moisture convergence on ice sheets provides an estimate of snow accumulation, which is critical to quantifying sea-level changes. In the case of East Antarctica, we computed moisture transport from 1980 to 2016 in five reanalyses and in radiosonde observations. Moisture convergence in reanalyses is more consistent than net precipitation but still ranges from 72 to 96 mm yr−1 in the four most recent reanalyses, ERA-Interim, NCEP CFSR, JRA 55 and MERRA 2. The representation of long-term variability in reanalyses is also inconsistent, which justified resorting to observations. Moisture fluxes are measured on a daily basis via radiosondes launched from a network of stations surrounding East Antarctica. Observations agree with reanalyses on the major role of extreme advection events and transient eddy fluxes. Although assimilated, the observations reveal processes that reanalyses cannot model, some due to a lack of horizontal and vertical resolution, especially the oldest, NCEP DOE R2. Additionally, the observational time series are not affected by new satellite data unlike the reanalyses. We formed pan-continental estimates of convergence by aggregating anomalies from all available stations. We found statistically significant trends neither in moisture convergence nor in precipitable water.

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