Subcritical instability and hysteresis in a two-layer model

Sukyoung Lee, I. M. Held

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

A two-layer quasi-geostrophic model forced by surface friction and radiative relaxation to a jetlike wind profile can exist in either a wave-free state or in a finite-amplitude wave state, over a substantial region of the models parameter space. Weakly unstable waves are found that do not stabilize the flow; instead, their growth rate increases with wave amplitude. We explain this is terms of 1) the competition between the stabilizing effect of the lower-layer potential vorticity fluxes and the destabilizing effect of nonlinear critical layer formation associated with the upper-layer fluxes, and 2) the tendency of surface drag to restore the vertical shear at the center of the jet by damping the surface westerlies generated by the baroclinic instability. -from Authors

Original languageEnglish (US)
Pages (from-to)1071-1077
Number of pages7
JournalJournal of the Atmospheric Sciences
Volume48
Issue number8
StatePublished - Jan 1 1991

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hysteresis
baroclinic instability
wind profile
potential vorticity
damping
drag
friction
effect

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

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Subcritical instability and hysteresis in a two-layer model. / Lee, Sukyoung; Held, I. M.

In: Journal of the Atmospheric Sciences, Vol. 48, No. 8, 01.01.1991, p. 1071-1077.

Research output: Contribution to journalArticle

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AU - Held, I. M.

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AB - A two-layer quasi-geostrophic model forced by surface friction and radiative relaxation to a jetlike wind profile can exist in either a wave-free state or in a finite-amplitude wave state, over a substantial region of the models parameter space. Weakly unstable waves are found that do not stabilize the flow; instead, their growth rate increases with wave amplitude. We explain this is terms of 1) the competition between the stabilizing effect of the lower-layer potential vorticity fluxes and the destabilizing effect of nonlinear critical layer formation associated with the upper-layer fluxes, and 2) the tendency of surface drag to restore the vertical shear at the center of the jet by damping the surface westerlies generated by the baroclinic instability. -from Authors

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