The role of the turbulent stress divergence in the equatorial Pacific zonal momentum balance

1991 ◽  
Vol 96 (C4) ◽  
pp. 7127 ◽  
Author(s):  
D. Hebert ◽  
J. N. Moum ◽  
C. A. Paulson ◽  
D. R. Caldwell ◽  
T. K. Chereskin ◽  
...  
Keyword(s):  
Equatorial Pacific ◽  
Momentum Balance ◽  
Turbulent Stress ◽  
Zonal Momentum Balance ◽  
Zonal Momentum

scholarly journals A finite-difference convective model for Jupiter's equatorial jet

2006 ◽  
Vol 2 (S239) ◽  
pp. 230-232 ◽  
Author(s):  
Kwing L. Chan
Keyword(s):  
Reynolds Number ◽  
Numerical Model ◽  
Finite Difference ◽  
Spherical Shell ◽  
Reynolds Stress ◽  
Momentum Equation ◽  
Momentum Balance ◽  
Zonal Momentum Balance ◽  
Zonal Momentum ◽  
Convective Model

AbstractWe present results of a numerical model for studying the dynamics of Jupiter's equatorial jet. The computed domain is a piece of spherical shell around the equator. The bulk of the region is convective, with a thin radiative layer at the top. The shell is spinning fast, with a Coriolis number = ΩL/V on the order of 50. A prominent super-rotating equatorial jet is generated, and secondary alternating jets appear in the higher latitudes. The roles of terms in the zonal momentum equation are analyzed. Since both the Reynolds number and the Taylor number are large, the viscous terms are small. The zonal momentum balance is primarily between the Coriolis and the Reynolds stress terms.

Zonal Momentum Balance at the Equator

1989 ◽  
Vol 19 (5) ◽  
pp. 561-570 ◽  
Author(s):  
T. M. Dillon ◽  
J. N. Moum ◽  
T. K. Chereskin ◽  
D. R. Caldwell
Keyword(s):  
Momentum Balance ◽  
Zonal Momentum Balance ◽  
Zonal Momentum

scholarly journals Is the Coefficient of Eddy Potential Vorticity Diffusion Positive? Part I: Barotropic Zonal Channel

2018 ◽  
Vol 48 (7) ◽  
pp. 1589-1607 ◽  
Author(s):  
V. O. Ivchenko ◽  
V. B. Zalesny ◽  
B. Sinha
Keyword(s):  
Potential Vorticity ◽  
Independent Solution ◽  
Zonal Flow ◽  
Momentum Balance ◽  
Eddy Fluxes ◽  
The Mean ◽  
Zonal Momentum Balance ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Zonal Momentum

AbstractThe question of whether the coefficient of diffusivity of potential vorticity by mesoscale eddies is positive is studied for a zonally reentrant barotropic channel using the quasigeostrophic approach. The topography is limited to the first mode in the meridional direction but is unlimited in the zonal direction. We derive an analytic solution for the stationary (time independent) solution. New terms associated with parameterized eddy fluxes of potential vorticity appear both in the equations for the mean zonal momentum balance and in the kinetic energy balance. These terms are linked with the topographic form stress exerted by parameterized eddies. It is demonstrated that in regimes with zonal flow (analogous to the Antarctic Circumpolar Current), the coefficient of eddy potential vorticity diffusivity must be positive.

scholarly journals Zonal Momentum Balance, Potential Vorticity Dynamics, and Mass Fluxes on Near-Surface Isentropes

2005 ◽  
Vol 62 (6) ◽  
pp. 1884-1900 ◽  
Author(s):  
Tapio Schneider
Keyword(s):  
Potential Vorticity ◽  
Momentum Balance ◽  
Near Surface ◽  
Global Circulation ◽  
Balance Condition ◽  
Mass Fluxes ◽  
Vorticity Dynamics ◽  
The Mean ◽  
Zonal Momentum Balance ◽  
Zonal Momentum

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.

scholarly journals A Zonal Momentum Balance on Density Layers for the Central and Eastern Equatorial Pacific

2007 ◽  
Vol 37 (7) ◽  
pp. 1939-1955 ◽  
Author(s):  
Jaclyn N. Brown ◽  
J. Stuart Godfrey ◽  
Russell Fiedler
Keyword(s):  
Nonlinear Term ◽  
Baroclinic Instability ◽  
Three Dimensional ◽  
Momentum Equation ◽  
Surface Flow ◽  
Equatorial Pacific ◽  
Momentum Balance ◽  
Equatorial Pacific Ocean ◽  
Geostrophic Flow ◽  
Zonal Momentum

Abstract Brown et al. analyzed the kinematics of flow in the equatorial Pacific Ocean, along time-varying isopycnals in a three-dimensional eddy-permitting model. Here the dynamics of these flows is explored in the same model via the zonal momentum equation (ZME). Previous work has shown that the dominant terms of the ZME, on and near the equator, are the pressure gradient, wind stress, and Coriolis term. In one model study, the nonlinear and friction terms were significant but negated each other. In this study, with a higher-resolution model and more realistic friction scheme it is shown that the nonlinear term is important along and north of the equator, while the explicit friction term is negligible. The part of the nonlinear term derived from high-frequency eddy flows acts like a friction on the Equatorial Undercurrent, while the remaining part of the nonlinear term from smooth flows enhances it. In density coordinates, meridional tropical cells lie on either side of the equator in the first half of the year (January–June) as expected. In July–December, a continuous southward surface flow appears from 4°N into the Southern Hemisphere and arises from variations in the geostrophic flow and the nonlinear term. Variations in the geostrophic flow are due to both seasonal variability in the thermocline and a surface bolus effect arising from baroclinic instability. The nonlinear term increases in the surface layers at the same time assisting the southward flow, most likely because of tropical instability waves.

Tropical Zonal Momentum Balance in the NCEP Reanalyses

2005 ◽  
Vol 62 (7) ◽  
pp. 2499-2513 ◽  
Author(s):  
Ioana M. Dima ◽  
John M. Wallace ◽  
Ian Kraucunas
Keyword(s):  
Rossby Wave ◽  
Wave Pattern ◽  
Reanalysis Data ◽  
Momentum Balance ◽  
Stationary Waves ◽  
Upper Troposphere ◽  
The Cross ◽  
Zonal Momentum Balance ◽  
Zonal Momentum ◽  
Tropical Upper Troposphere

Abstract The seasonal cycle of the zonal-mean zonal momentum balance in the Tropics is investigated using NCEP reanalysis data. It is found that the climatological stationary waves in the tropical upper troposphere, which are dominated by the equatorial Rossby wave response to tropical heating, produce an equatorward eddy flux of westerly momentum in the equatorial belt. The resulting westerly acceleration in the tropical upper troposphere is balanced by the advection of easterly momentum associated with the cross-equatorial mean meridional circulation. The eddy momentum fluxes and the cross-equatorial flow both tend to be strongest during the monsoon seasons, when the maximum diabatic heating is off the equator, and weakest during April–May, the season of strongest equatorial symmetry of the heating. The upper-level Rossby wave pattern exhibits a surprising degree of equatorial symmetry and follows a similar seasonal progression. Solutions of the nonlinear shallow water wave equation also show a predominantly equatorially symmetric response to a heat source centered off the equator.

scholarly journals Acceleration of the Antarctic Circumpolar Current by Wind Stress along the Coast of Antarctica

2013 ◽  
Vol 43 (12) ◽  
pp. 2772-2784 ◽  
Author(s):  
Jan D. Zika ◽  
Julien Le Sommer ◽  
Carolina O. Dufour ◽  
Alberto Naveira-Garabato ◽  
Adam Blaker
Keyword(s):  
Antarctic Circumpolar Current ◽  
Momentum Balance ◽  
Quasi Equilibrium ◽  
Two Factors ◽  
Free Mode ◽  
Zonal Momentum Balance ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Balance Mechanism ◽  
Zonal Momentum

Abstract The influence of wind forcing on variability of the Antarctic Circumpolar Current (ACC) is investigated using a series of eddy-permitting ocean–sea ice models. At interannual and decadal time scales the ACC transport is sensitive to both the mean strength of westerly winds along the ACC circumpolar path, consistent with zonal momentum balance theories, and sensitive to the wind stresses along the coast of Antarctica, consistent with the “free mode” theory of Hughes et al. A linear combination of the two factors explains differences in ACC transport across 11 regional quasi-equilibrium experiments. Repeated single-year global experiments show that the ACC can be robustly accelerated by both processes. Across an ensemble of simulations with realistic forcing over the second half of the twentieth century, interannual ACC transport variability owing to the free-mode mechanism exceeds that due to the zonal momentum balance mechanism by a factor of between 3.5 and 5 to one. While the ACC transport may not accelerate significantly owing to projected increases in along-ACC winds in future decades, significant changes in transport could still occur because of changes in the stress along the coast of Antarctica.

scholarly journals Hadley Cell Dynamics in a Virtually Dry Snowball Earth Atmosphere

2012 ◽  
Vol 69 (1) ◽  
pp. 116-128 ◽  
Author(s):  
Aiko Voigt ◽  
Isaac M. Held ◽  
Jochem Marotzke
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Hadley Cell ◽  
Snowball Earth ◽  
Momentum Balance ◽  
Earth Atmosphere ◽  
Vertical Diffusion ◽  
Zonal Momentum Balance ◽  
Dry Convection ◽  
Zonal Momentum

Abstract The Hadley cell of a virtually dry snowball Earth atmosphere under equinox insolation is studied in a comprehensive atmospheric general circulation model. In contrast to the Hadley cell of modern Earth, momentum transport by dry convection, which is modeled as vertical diffusion of momentum, is important in the upper branch of the snowball Earth Hadley cell. In the zonal momentum balance, mean meridional advection of mean absolute vorticity is not only balanced by eddies but also by vertical diffusion of zonal momentum. Vertical diffusion also contributes to the meridional momentum balance by decelerating the Hadley cell through downgradient mixing of meridional momentum between its upper and lower branches. When vertical diffusion of momentum is suppressed in the upper branch, the Hadley cell strengthens by a factor of about 2. This is in line with the effect of vertical diffusion in the meridional momentum balance but in contrast with its effect in the zonal momentum balance. Neither axisymmetric Hadley cell theories based on angular momentum conservation nor eddy-permitting Hadley cell theories that neglect vertical diffusion of momentum are applicable to the snowball Earth Hadley cell. Because the snowball Earth Hadley cell is a particular realization of a dry Hadley cell, these results show that an appropriate description of dry Hadley cells should take into account vertical transport of momentum by dry convection.

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