Nonlinear resonance and instability of planetary waves and low-frequency variability in the atmosphere

Journal Article · Mon Nov 01 04:00:00 EST 1993 · Journal of the Atmospheric Sciences; (United States)

DOI:https://doi.org/10.1175/1520-0469(1993)050<3590:NRAIOP>2.0.CO;2· OSTI ID:5645019

Wu, P ^[1]

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1. Imperial College, London (United Kingdom)

It is demonstrated in this work that linearly unstable planetary waves can be resonantly excited to finite amplitude in a nonlinear barotropic atmosphere with vorticity forcing and dissipation. In a weakly forced/dissipated atmosphere, it is shown that barotropic instability may provide a dynamic mechanism of transition between different [open quotes]flow regimes.[close quotes] It is suggested that nonlinear resonance and instability of planetary waves, which seem to be common with finite amplitude steady free solutions, may play a role in producing low-frequency variability observed in the real atmosphere. A type of nonlinear free solution with realistically sheared zonal flow is described in spherical geometry, and normal-mode instability analysis is performed to examine its stability. A time-dependent spectral model is employed to demonstrate the resonant excitation and breakdown of unstable planetary waves that results in low-frequency variability. The steady free solution is barotropically unstable to large-scale, low-frequency perturbations. Even though unstable, it can be resonantly excited from many initial conditions by a stationary vorticity forcing that projects onto it. The leading low-frequency oscillation has a period of about 20 days and the model flow hemispherically alternates between an almost zonal flow and a blocking regime, reminiscent of the multiple equilibria found by Charney and DeVore. 25 refs., 37 figs., 1 tab.

• OSTI ID: 5645019
• Journal Information: Journal of the Atmospheric Sciences; (United States), Journal Name: Journal of the Atmospheric Sciences; (United States) Vol. 50:21; ISSN 0022-4928; ISSN JAHSAK
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
ATMOSPHERIC CIRCULATION
DIFFERENTIAL EQUATIONS
EARTH ATMOSPHERE
EQUATIONS
FLUID FLOW
FUNCTIONS
GRAVITY WAVES
LEGENDRE POLYNOMIALS
NONLINEAR PROBLEMS
PARTIAL DIFFERENTIAL EQUATIONS
POLYNOMIALS
RESONANCE
TIME DEPENDENCE
VORTEX FLOW
WAVE EQUATIONS