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A Gravity Wave Drag Matrix for Complex Terrain.
- Source :
- Journal of the Atmospheric Sciences; Aug2018, Vol. 75 Issue 8, p2599-2613, 15p
- Publication Year :
- 2018
-
Abstract
- We propose a simplified scheme to predict mountain wave drag over complex terrain using only the regional-average low-level wind components U and V. The scheme is tuned and tested on data from the South Island of New Zealand, a rough and highly anisotropic terrain. The effect of terrain anisotropy is captured with a hydrostatically computed, 2 3 2 positive-definite wave drag matrix. The wave drag vector is the product of the wind vector and the drag matrix. The nonlinearity in wave generation is captured using a Gaussian terrain smoothing inversely proportional to wind speed. Wind speeds of |U| 5 10, 20, and 30 m s<superscript>1</superscript> give smoothing scales of L 5 54, 27, and 18 km, respectively. This smoothing treatment of nonlinearity is consistent with recent aircraft data and high-resolution numerical modeling of waves over New Zealand, indicating that the momentum flux spectra shift to shorter waves during high-drag conditions. The drag matrix model is tested against a 3-month time series of realistic full-physics wave-resolving flow calculations. Correlation coefficients approach 0.9 for both zonal and meridional drag components. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00224928
- Volume :
- 75
- Issue :
- 8
- Database :
- Complementary Index
- Journal :
- Journal of the Atmospheric Sciences
- Publication Type :
- Academic Journal
- Accession number :
- 131062961
- Full Text :
- https://doi.org/10.1175/JAS-D-17-0380.1