The Generation of Lee Waves by the Blue Ridge

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  • 1 Department of Astro-Geophysics, University Of Colorado, Boulder 80302
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Abstract

This study focuses on the flow over a low, straight section of the Blue Ridge Mountain in the central Appalachians. Aircraft measurements, laboratory simulation, and mathematical analysis using both the linearized equations and the nonlinear hydrostatic equations, are compared. Aircraft observations of a Blue Ridge lee wave indicate that the linear theory correctly predicts the wavelength but badly under-estimates the wave amplitude. This discrepancy is confirmed in the laboratory. It appears that the discrepancy can be accounted for by the effects of a strong nonlinearity in the governing equations. It is suggested that nonlinear effects acting near the mountain can be important for wave generation and that Long's model is restrictive as it includes only the cases for which this aspect of the physics is entirely absent.

Abstract

This study focuses on the flow over a low, straight section of the Blue Ridge Mountain in the central Appalachians. Aircraft measurements, laboratory simulation, and mathematical analysis using both the linearized equations and the nonlinear hydrostatic equations, are compared. Aircraft observations of a Blue Ridge lee wave indicate that the linear theory correctly predicts the wavelength but badly under-estimates the wave amplitude. This discrepancy is confirmed in the laboratory. It appears that the discrepancy can be accounted for by the effects of a strong nonlinearity in the governing equations. It is suggested that nonlinear effects acting near the mountain can be important for wave generation and that Long's model is restrictive as it includes only the cases for which this aspect of the physics is entirely absent.

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