scholarly journals Quantifying advective and nonstationary effects on eddy fluxes in the AmeriFlux network

2012 ◽  
Author(s):  
David R Fitzjarrald
2016 ◽  
Vol 46 (6) ◽  
pp. 1963-1985 ◽  
Author(s):  
Lei Wang ◽  
Malte Jansen ◽  
Ryan Abernathey

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.


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

2008 ◽  
Vol 21 (12) ◽  
pp. 2770-2789 ◽  
Author(s):  
Raffaele Ferrari ◽  
James C. McWilliams ◽  
Vittorio M. Canuto ◽  
Mikhail Dubovikov

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.


2014 ◽  
Vol 44 (3) ◽  
pp. 922-943 ◽  
Author(s):  
V. O. Ivchenko ◽  
S. Danilov ◽  
B. Sinha ◽  
J. Schröter

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.


Author(s):  
Ross M. Evan-Iwanowski ◽  
J. F. Nayfeh ◽  
C. H. Lu

Abstract The system in the title has been subjected to a parametric, nonstationary (NS) linear v(t) = v0 + βt, and cyclic v(t) = v0 ± γ sin βt excitations. The NS linear responses settle on the initial, constant values for extended values of the excitation frequencies, thus they stabilize the stationary (ST) response. This is true for the initial conditions taken on the stationary curve, and for different ply-angles. For the initial conditions (I.C.) beyond the ST plots, the NS responses stay also near the initial conditions, but they have the wavy forms, which increase slightly for the lower values of the forcing frequencies. For the cyclic parametric excitations, the NS responses are cyclic contained within the ranges of the excitation amplitudes ±β and (finite) response amplitudes above the ST initial values, raising up and down within these limits. It appears that they cover the whole area within the above described constraints. The decisive effect of the cyclic NS inputs, i.e., almost instantaneous cyclic responses replacing the ST responses regardless of the I.C. and ST responses, is a bench mark of the cyclic NS. This behavior is distinctly different from the NS cyclic responses of the composite columns.


2015 ◽  
Vol 82 (2) ◽  
pp. 286-292 ◽  
Author(s):  
N. Silsirivanich ◽  
D. Chenvidhya ◽  
K. Kirtikara ◽  
K. Sriprapha ◽  
J. Sritharathikhun ◽  
...  

Author(s):  
V. O. Ivchenko ◽  
V. B. Zalesny

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.


2013 ◽  
Vol 25 (3) ◽  
pp. 433-444 ◽  
Author(s):  
João Marcos Azevedo Correia De Souza ◽  
Afonso De Moraes Paiva ◽  
Karina Von Schuckmann

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.


1994 ◽  
Vol 72 (8) ◽  
pp. 1208-1211 ◽  
Author(s):  
J. P. Matte ◽  
J. C. Kieffer ◽  
S. Ethier ◽  
M. Chaker ◽  
O. Peyrusse

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