Lower-Tropospheric Eddy Momentum Fluxes in Idealized Models and Reanalysis Data

Lower-Tropospheric Eddy Momentum Fluxes in Idealized Models and Reanalysis Data AbstractIn Earth’s atmosphere eddy momentum fluxes (EMFs) are largest in the upper troposphere, but EMFs in the lower troposphere, although modest in amplitude, have an intriguing structure. To document this structure, the EMFs in the lower tropospheres of a two-layer quasigeostrophic model, a primitive equation model, and the Southern Hemisphere of a reanalysis dataset are investigated. The lower-tropospheric EMFs are very similar in the cores of the jets in both models and the reanalysis data, with EMF divergence (opposing the upper-tropospheric convergence) due to relatively long waves with slow eastward phase speeds and EMF divergence (as in the upper troposphere) due to shorter waves with faster eastward phase speeds.As the two-layer model is able to capture the EMF divergence by long waves, a qualitative picture of the underlying dynamics is proposed that relies on the negative potential vorticity gradient in the lower layer of the model. Eddies excited by baroclinic instability mix efficiently through a wide region in the lower layer, centered on the latitude of maximum westerlies and encompassing the lower-layer critical latitudes. Near these critical latitudes, the mixing is enhanced, resulting in increased EMF convergence, with compensating EMF divergence in the center of the jet. The EMF convergence at faster phase speeds is due to deep eddies that propagate on the upper-tropospheric potential vorticity gradient. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of the Atmospheric Sciences American Meteorological Society

Lower-Tropospheric Eddy Momentum Fluxes in Idealized Models and Reanalysis Data

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0469
DOI
10.1175/JAS-D-17-0099.1
Publisher site
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Abstract

AbstractIn Earth’s atmosphere eddy momentum fluxes (EMFs) are largest in the upper troposphere, but EMFs in the lower troposphere, although modest in amplitude, have an intriguing structure. To document this structure, the EMFs in the lower tropospheres of a two-layer quasigeostrophic model, a primitive equation model, and the Southern Hemisphere of a reanalysis dataset are investigated. The lower-tropospheric EMFs are very similar in the cores of the jets in both models and the reanalysis data, with EMF divergence (opposing the upper-tropospheric convergence) due to relatively long waves with slow eastward phase speeds and EMF divergence (as in the upper troposphere) due to shorter waves with faster eastward phase speeds.As the two-layer model is able to capture the EMF divergence by long waves, a qualitative picture of the underlying dynamics is proposed that relies on the negative potential vorticity gradient in the lower layer of the model. Eddies excited by baroclinic instability mix efficiently through a wide region in the lower layer, centered on the latitude of maximum westerlies and encompassing the lower-layer critical latitudes. Near these critical latitudes, the mixing is enhanced, resulting in increased EMF convergence, with compensating EMF divergence in the center of the jet. The EMF convergence at faster phase speeds is due to deep eddies that propagate on the upper-tropospheric potential vorticity gradient.

Journal

Journal of the Atmospheric Sciences – American Meteorological Society

Published: Nov 3, 2017

References

  • Why eddy momentum fluxes are concentrated in the upper troposphere
    Ait-Chaalal, F.; Schneider, T.
  • Horizontal structure of 500 mb height fluctuations with long, intermediate and short time scales
    Blackmon, M. L.; Lee, Y. H.; Wallace, J. M.
  • Equilibration of a baroclinic planetary atmosphere toward the limit of vanishing bottom friction
    Chai, J.; Jansen, M.; Vallis, G. K.
  • Sensitivity of the latitude of the surface westerlies to surface friction
    Chen, G.; Plumb, R. A.
  • Sensitivity of the latitude of the surface westerlies to surface friction
    Chen, G.; Held, I. M.; Robinson, W. A.
  • A simple model for transient eddy momentum fluxes in the upper troposphere
    DelSole, T.
  • Stochastic dynamics of the midlatitude atmospheric jet
    Farrell, B. F.; Ioannou, P. J.
  • An observational study of the intraseasonal poleward propagation of zonal mean flow anomalies
    Feldstein, S. B.
  • Is the atmospheric zonal index driven by an eddy feedback?
    Feldstein, S. B.; Lee, S.
  • A generalized method of resolving disturbances into progressive and retrogressive waves by space Fourier and time cross-spectral analyses
    Hayashi, Y.
  • Momentum transport by quasi-geostrophic eddies
    Held, I. M.
  • A proposal for the intercomparison of the dynamical cores of atmospheric general circulation models
    Held, I. M.; Suarez, M. J.
  • A scaling theory for horizontally homogeneous, baroclinically unstable flow on a beta plane
    Held, I. M.; Larichev, V. D.
  • The shape, propagation and mean-flow interaction of large-scale weather systems
    Hoskins, B. J.; James, I. N.; White, G. H.
  • Can the increase in the eddy length scale under global warming cause the poleward shift of the jet streams?
    Kidston, J.; Vallis, G. K.; Dean, S. M.; Renwick, J. A.
  • The wave–zonal mean flow interaction in the Southern Hemisphere
    Kim, H.-K.; Lee, S.
  • Maintenance of multiple jets in a baroclinic flow
    Lee, S.
  • Finite-amplitude equilibration of baroclinic waves on a jet
    Lee, S.
  • Baroclinic wave packets in models and observations
    Lee, S.; Held, I. M.
  • Eddy–zonal flow feedback in the Southern Hemisphere
    Lorenz, D. J.; Hartmann, D. L.
  • Applying the fluctuation–dissipation theorem to a two-layer model of quasi-geostrophic turbulence
    Lutsko, N. J.; Held, I. M.; Zurita-Gotor, P.
  • Jet interaction and the influence of a minimum phase speed bound on the propagation of eddies
    O’Rourke, A. K.; Vallis, G. K.
  • Meridional Rossby wave generation and propagation in the maintenance of the wintertime tropospheric double jet
    O’Rourke, A. K.; Vallis, G. K.
  • The diffusive approximation for eddy fluxes in baroclinically unstable jets
    Pavan, V.; Held, I. M.
  • The general circulation of the atmosphere: A numerical experiment
    Phillips, N.
  • Phase speed spectra of transient eddy fluxes and critical layer absorption
    Randel, W. J.; Held, I. M.
  • MERRA: NASA’s Modern-Era Retrospective Analysis for Research and Applications
    Rienecker, M. M.
  • On the self-maintenance of midlatitude jets
    Robinson, W. A.
  • Equatorial superrotation and maintenance of the general circulation in two-level models
    Saravanan, R.
  • The relation between baroclinic adjustment and turbulent diffusion in the two-layer model
    Zurita-Gotor, P.
  • On the sensitivity of zonal-index persistence to friction
    Zurita-Gotor, P.
  • The impact of baroclinic eddy feedback on the persistence of jet variability in the two-layer model
    Zurita-Gotor, P.; Blanco-Fuentes, J.; Gerber, E. P.

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