On the Influence of Swell Propagation Angle on Surface Drag
- National Center for Atmospheric Research, Boulder, Colorado
- NorthWest Research Associates, Corvallis, Oregon
- Vestas Wind Systems A/S, Arhaus, Denmark
A combination of turbulence-resolving large-eddy simulations and observations are used to examine the influence of swell amplitude and swell propagation angle on surface drag. Based on the analysis a new surface roughness parameterization with nonequilibrium wave effects is proposed. The surface roughness accounts for swell amplitude and wavelength and its relative motion with respect to the mean wind direction. The proposed parameterization is tested in uncoupled three-dimensional Weather and Research Forecasting (WRF) simulations at grid sizes near 1 km where we explore potential implications of our modifications for two-way coupled atmosphere–wave models. Wind–wave misalignment likely explains the large scatter in observed nondimensional surface roughness under swell-dominated conditions. Andreas et al.’s relationship between friction velocity and the 10-m wind speed under predicts the increased drag produced by misaligned winds and waves. Incorporating wave-state (speed and direction) influences in parameterizations improves predictive skill. In a broad sense, these results suggest that one needs information on winds and wave state to upscale buoy measurements.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- Grant/Contract Number:
- AC02-05CH11231; EE0005373
- OSTI ID:
- 1510157
- Alternate ID(s):
- OSTI ID: 1527380
- Journal Information:
- Journal of Applied Meteorology and Climatology, Journal Name: Journal of Applied Meteorology and Climatology Journal Issue: 5 Vol. 58; ISSN 1558-8424
- Publisher:
- American Meteorological SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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