An analytical model of mountain wave drag for wind profiles with shear and curvature

• Type: Article in International Scientific Journal
• Date: 2004

Authors

Teixeira, MAC (Author) Other; Miranda, PMA (Author) Other; Valente, MA (Author) Other

Journal

The Journal is awaiting validation by the Administrative Services.

Title: JOURNAL OF THE ATMOSPHERIC SCIENCES

Vol. 61

Pages: 1040-1054

ISSN: 0022-4928

Indexing

ISI Web of Knowledge - 35 Citations

Scopus - 37 Citations

Other information

Authenticus ID: P-000-AN1

DOI: 10.1175/1520-0469(2004)061<1040:aamomw>2.0.co;2

Abstract (EN): An analytical model is developed to predict the surface drag exerted by internal gravity waves on an isolated axisymmetric mountain over which there is a stratified flow with a velocity profile that varies relatively slowly with height. The model is linear with respect to the perturbations induced by the mountain, and solves the Taylor - Goldstein equation with variable coefficients using a Wentzel - Kramers - Brillouin (WKB) approximation, formally valid for high Richardson numbers, Ri. The WKB solution is extended to a higher order than in previous studies, enabling a rigorous treatment of the effects of shear and curvature of the wind profile on the surface drag. In the hydrostatic approximation, closed formulas for the drag are derived for generic wind profiles, where the relative magnitude of the corrections to the leading-order drag ( valid for a constant wind profile) does not depend on the detailed shape of the orography. The drag is found to vary proportionally to Ri(-1), decreasing as Ri decreases for a wind that varies linearly with height, and increasing as Ri decreases for a wind that rotates with height maintaining its magnitude. In these two cases the surface drag is predicted to be aligned with the surface wind. When one of the wind components varies linearly with height and the other is constant, the surface drag is misaligned with the surface wind, especially for relatively small Ri. All these results are shown to be in fairly good agreement with numerical simulations of mesoscale nonhydrostatic models, for high and even moderate values of Ri.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 15