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 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.

scholarly journals Relation Between the Interannual Variability in the Stratospheric Rossby Wave Forcing and Zonal Mean Fields Suggesting an Interhemispheric Link in the Stratosphere

2019 ◽  
Author(s):  
Yuki Matsushita ◽  
Daiki Kado ◽  
Masashi Kohma ◽  
Kaoru Sato
Keyword(s):  
Interannual Variability ◽  
Rossby Wave ◽  
Reanalysis Data ◽  
Mean Flow ◽  
Flux Divergence ◽  
Wave Forcing ◽  
Mean Fields ◽  
Meridional Cross Section ◽  
The Cross ◽  
Modern Era

Abstract. Focusing on the interannual variabilities in the zonal mean fields and Rossby wave forcing in austral winter, an interhemispheric coupling in the stratosphere is examined using reanalysis data: the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). In the present study, the Eliassen-Palm (EP) flux divergence averaged over the latitude and height regions of 50°–30° S and 0.3–1 hPa, respectively, are used as a proxy of the Rossby wave forcing, where the absolute value of the EP flux divergence is maximized in the winter in the Southern Hemisphere (SH). The interannual variabilities in the zonal mean temperature and zonal wind are significantly correlated with the SH Rossby wave forcing in the stratosphere in both the SH and Northern Hemisphere (NH). The interannual variability in the strength of the poleward residual mean flow in the SH stratosphere is also correlated with the strength of the wave forcing. This correlation is significant even around the equator at an altitude of 40 km and at NH low latitudes of 20–40 km. The temperature anomaly is consistent with this residual mean flow anomaly. The relationship between the cross-equatorial flow and the zonal mean absolute angular momentum gradient (My) is examined in the meridional cross section. The My around the equator at the altitude of 40 km is small when the wave forcing is strong, which provides a pathway for the cross-equatorial residual mean flow. These results indicate that an interhemispheric coupling is present in the stratosphere through the meridional circulation modulated by the Rossby wave forcing.

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 Relation between the interannual variability in the stratospheric Rossby wave forcing and zonal mean fields suggesting an interhemispheric link in the stratosphere

2020 ◽  
Vol 38 (2) ◽  
pp. 319-329
Author(s):  
Yuki Matsushita ◽  
Daiki Kado ◽  
Masashi Kohma ◽  
Kaoru Sato
Keyword(s):  
Interannual Variability ◽  
Rossby Wave ◽  
Reanalysis Data ◽  
Mean Flow ◽  
Flux Divergence ◽  
Wave Forcing ◽  
Mean Fields ◽  
Meridional Cross Section ◽  
The Cross ◽  
Modern Era

Abstract. Focusing on the interannual variabilities in the zonal mean fields and Rossby wave forcing in austral winter, an interhemispheric coupling in the stratosphere is examined using reanalysis data: the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). In the present study, the Eliassen–Palm (EP) flux divergence averaged over the latitude and height regions of 50–30∘ S and 0.3–1 hPa, respectively, are used as a proxy of the Rossby wave forcing, where the absolute value of the EP flux divergence is maximized in the winter in the Southern Hemisphere (SH). The interannual variabilities in the zonal mean temperature and zonal wind are significantly correlated with the SH Rossby wave forcing in the stratosphere in both the SH and Northern Hemisphere (NH). The interannual variability in the strength of the poleward residual mean flow in the SH stratosphere is also correlated with the strength of the wave forcing. This correlation is significant even around the Equator at an altitude of 40 km and at NH low latitudes of 20–40 km. The temperature anomaly is consistent with this residual mean flow anomaly. The relation between the cross-equatorial flow and the zonal mean absolute angular momentum gradient (M‾y) is examined in the meridional cross section. The M‾y around the Equator at the altitude of 40 km is small when the wave forcing is strong, which provides a pathway for the cross-equatorial residual mean flow. These results indicate that an interhemispheric coupling is present in the stratosphere through the meridional circulation modulated by the Rossby wave forcing.

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
Sign in / Sign up

Export Citation Format

Share Document