The importance of friction in mountain wave drag amplification by Scorer parameter resonance

• Type: Article in International Scientific Journal
• Date: 2012

Authors

Teixeira, MAC (Author) Other; Arga'in, JL (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. 138

Pages: 1325-1337

ISSN: 0035-9009

Indexing

ISI Web of Knowledge - 8 Citations

Scopus - 8 Citations

Other information

Authenticus ID: P-002-8AY

DOI: 10.1002/qj.1874

Abstract (EN): A mechanism for amplification of mountain waves, and their associated drag, by parametric resonance is investigated using linear theory and numerical simulations. This mechanism, which is active when the Scorer parameter oscillates with height, was recently classified by previous authors as intrinsically nonlinear. Here it is shown that, if friction is included in the simplest possible form as a Rayleigh damping, and the solution to the TaylorGoldstein equation is expanded in a power series of the amplitude of the Scorer parameter oscillation, linear theory can replicate the resonant amplification produced by numerical simulations with some accuracy. The drag is significantly altered by resonance in the vicinity of n/l0 = 2, where l0 is the unperturbed value of the Scorer parameter and n is the wave number of its oscillation. Depending on the phase of this oscillation, the drag may be substantially amplified or attenuated relative to its non-resonant value, displaying either single maxima or minima, or double extrema near n/l0 = 2. Both non-hydrostatic effects and friction tend to reduce the magnitude of the drag extrema. However, in exactly inviscid conditions, the single drag maximum and minimum are suppressed. As in the atmosphere friction is often small but non-zero outside the boundary layer, modelling of the drag amplification mechanism addressed here should be quite sensitive to the type of turbulence closure employed in numerical models, or to computational dissipation in nominally inviscid simulations. Copyright (c) 2012 Royal Meteorological Society

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 13