Orographic Drag Associated with Lee Waves Trapped at an Inversion

• Type: Article in International Scientific Journal
• Date: 2013

Authors

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

Journal

The Journal is awaiting validation by the Administrative Services.

Title: JOURNAL OF THE ATMOSPHERIC SCIENCES

Vol. 70

Pages: 2930-2947

ISSN: 0022-4928

Indexing

ISI Web of Knowledge - 25 Citations

Scopus - 26 Citations

Other information

Authenticus ID: P-006-7T0

DOI: 10.1175/jas-d-12-0350.1

Abstract (EN): The drag produced by 2D orographic gravity waves trapped at a temperature inversion and waves propagating in the stably stratified layer existing above are explicitly calculated using linear theory, for a two-layer atmosphere with neutral static stability near the surface, mimicking a well-mixed boundary layer. For realistic values of the flow parameters, trapped-lee-wave drag, which is given by a closed analytical expression, is comparable to propagating-wave drag, especially in moderately to strongly nonhydrostatic conditions. In resonant flow, both drag components substantially exceed the single-layer hydrostatic drag estimate used in most parameterization schemes. Both drag components are optimally amplified for a relatively low-level inversion and Froude numbers Fr approximate to 1. While propagating-wave drag is maximized for approximately hydrostatic flow, trapped-lee-wave drag is maximized for l(2)a = O(1) (where l(2) is the Scorer parameter in the stable layer and a is the mountain width). This roughly happens when the horizontal scale of trapped lee waves matches that of the mountain slope. The drag behavior as a function of Fr for l(2)H = 0.5 (where H is the inversion height) and different values of l(2)a shows good agreement with numerical simulations. Regions of parameter space with high trapped-lee-wave drag correlate reasonably well with those where lee-wave rotors were found to occur in previous nonlinear numerical simulations including frictional effects. This suggests that trapped-lee-wave drag, besides giving a relevant contribution to low-level drag exerted on the atmosphere, may also be useful to diagnose lee-rotor formation.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 18