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Assessing wind profile effects on the global atmospheric torque
Author(s) -
Miranda P. M. A.,
Martins J. P. A.,
Teixeira M. A. C.
Publication year - 2009
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.393
Subject(s) - wkb approximation , drag , wind shear , computation , angular momentum , torque , curvature , meteorology , mechanics , shear (geology) , physics , atmospheric sciences , environmental science , geology , classical mechanics , mathematics , wind speed , geometry , algorithm , quantum mechanics , thermodynamics , petrology
The impact of a new approach to the evaluation of surface gravity wave drag (GWD) is assessed. This approach uses linear theory, but incorporates the effects of wind profile shear and curvature, by means of a second‐order WKB approximation. While the theory predicts the possibility of either drag enhancement or reduction, depending on the wind profile, results obtained with the ERA‐40 reanalysis data clearly indicate the predominance of local drag enhancement. However, the global impact of shear on the atmospheric axial GWD torque comes mostly from regions with predominantly easterly flow, contributing to a slight reduction of the bias found in different studies of the global angular momentum budget. The relative correction due to shear on linear GWD is found not to depend too strongly on the levels chosen for the computation of the low‐level wind derivatives. Copyright © 2009 Royal Meteorological Society