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Description
Title Lee-Wave Resonances over Double Bell-Shaped Obstacles
Type Publication
Abstract:

Lee-wave resonance over double bell-shaped obstacles is investigated through a series of idealized high-resolution numerical simulations with the nonhydrostatic Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) model using a free-slip lower boundary condition. The profiles of wind speed and stability as well as terrain derive from observations of lee-wave events over the Sierra Nevada and Inyo Mountains from the recently completed Terrain-Induced Rotor Experiment (T-REX).
Numerical experiments show that double bell-shaped obstacles promote trapped lee waves that are in general shorter than those excited by an isolated ridge. While the permissible trapped lee-wave modes are determined by the upstream atmospheric structure, primarily vertical wind shear, the selected lee-wave wavelengths for two obstacles that are close or equal in height are dictated by the discrete terrain spectrum and correspond to higher harmonics of the primary orographic wavelength, which is equal to the ridge separation distance. The exception is the smallest ridge separation distance examined, one that corresponds to the Owens Valley width and is closest to the wavelength determined by the given upstream atmospheric structure, for which the primary lee-wave and orographic wavelengths were found to nearly coincide.
The influence two mountains exert on the overall lee-wave field is found to persist at very large ridge separation distances. For the nonlinear nonhydrostatic waves examined, the ridge separation distance is found to exert a much stronger control over the lee-wave wavelengths than the mountain half-width. Positive and negative interferences of lee waves, which can be detected through their imprint on wave drag and wave amplitudes, were found to produce appreciable differences in the flow structure mainly over the downstream peak, with negative interference characterized by a highly symmetric flow pattern leading to a low drag state.

Available from http://journals.ametsoc.org/doi/abs/10.1175/2008JAS2885.1
Author
V. Grubišić, I. Stiperski
Reference
Journal Journal of the Atmospheric Sciences
Volume 66
Pages 1205-1228
Year 2009
Times cited 0
Institute country United States
Type of science
  • Atmospheric dynamics (includes thermodynamics)
  • Ocean-Atmosphere interactions
Field of science
  • Troposphere
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Last update April 21, 2016, 11:18
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File name GrubisicStiperski_2009_JAS_20100412162006.pdf
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