A linear model of gravity wave drag for hydrostatic sheared flow over elliptical mountains

• Type: Article in International Scientific Journal
• Date: 2006

Authors

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

Journal

The Journal is awaiting validation by the Administrative Services.

Title: QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY

Vol. 132

Pages: 2439-2458

ISSN: 0035-9009

Indexing

ISI Web of Knowledge - 27 Citations

Scopus - 28 Citations

Other information

Authenticus ID: P-004-H22

DOI: 10.1256/qj.05.220

Abstract (EN): An analytical model of orographic gravity wave drag due to sheared flow past elliptical mountains is developed. The model extends the domain of applicability of the well-known Phillips model to wind profiles that vary relatively slowly in the vertical, so that they may be treated using a WKB approximation. The model illustrates how linear processes associated with wind profile shear and curvature affect the drag force exerted by the airflow on mountains, and how it is crucial to extend the WKB approximation to second order in the small perturbation parameter for these effects to be taken into account. For the simplest wind profiles, the normalized drag depends only on the Richardson number, Ri, of the flow at the surface and on the aspect ratio, gamma, of the mountain. For a linear wind profile, the drag decreases as Ri decreases, and this variation is faster when the wind is across the mountain than when it is along the mountain. For a wind that rotates with height maintaining its magnitude, the drag generally increases as Ri decreases, by an amount depending on gamma and on the incidence angle. The results from WKB theory are compared with exact linear results and also with results from a non-hydrostatic nonlinear numerical model, showing in general encouraging agreement, down to values of Ri of order one.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 20