The stationary response to large-scale orography in a general circulation model and a linear model

Journal Article · Sun Mar 15 00:00:00 EST 1992 · Journal of the Atmospheric Sciences; (United States)

DOI:https://doi.org/10.1175/1520-0469(1992)049<0525:TSRTLS>2.0.CO;2· OSTI ID:5583742

Cook, K H; Held, I M ^[1]

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1. Geophysical Fluid Dynamics Laboratory/NOAA, Princeton, NJ (United States)

Stationary waves generated over orography in a linear model and a general circulation model (GCM) are compared to examine how the atmosphere's response is established for small mountains and how linear theory breaks down over large orographic features. Both models have nine vertical levels and are low-resolution (R15) spectral models. The linear model solves the stationary linear primitive equations. The GCM's control integration uses zonally uniform and hemispherically symmetric boundary conditions, with a global swamp surface. Five experiments are performed by perturbing the GCM with Gaussian mountains of various heights introduced in midlatitudes. The stationary wave model is linearized about zonal mean fields from the GCM climatology. The linear model's response to a Gaussian mountain at 45[degrees]N latitude is dominated by a single wave train radiating toward the southeast. For mountain heights between 0.7 an 2 km, the GCM's stationary waves are similar to the linear model response to orography, although amplitudes increase less rapidly than linearly with mountain height. For larger mountains, closed isentropes and distinctly nonlinear flow occur along the surface of the mountain and a large poleward-radiating wave train develops. The development of closed isentropes, and the breakdown of linear theory, can be predicted whenever the slope of the surface exceeds the slope of the isentropes in the unperturbed (no mountain) basic state. 19 refs., 29 figs.

• OSTI ID: 5583742
• Journal Information: Journal of the Atmospheric Sciences; (United States), Vol. 49:6, Issue 6; ISSN 0022-4928
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
MOUNTAINS
ATMOSPHERIC CIRCULATION
METEOROLOGY
STATISTICAL MODELS
COMPARATIVE EVALUATIONS
BOUNDARY CONDITIONS
DISTURBANCES
GAUSS FUNCTION
GENERAL CIRCULATION MODELS
TIME DEPENDENCE
VORTEX FLOW
WAVE EQUATIONS
DIFFERENTIAL EQUATIONS
EQUATIONS
EVALUATION
FLUID FLOW
FUNCTIONS
MATHEMATICAL MODELS
PARTIAL DIFFERENTIAL EQUATIONS
540110*