Quantification of the Spatial Variability of the Ocean Surface Roughness and Momentum Flux
Abstract
It is well known that physical processes occurring at the air-sea interface, such as air-sea mass, momentum, and energy exchanges, are controlled by the ocean surface roughness that has often been characterized in the literature as being homogeneous in space and time from a large-scale point of view. However, the ocean surface roughness is heterogeneous within a wavelength. The surface areas on wave crests are usually rougher than those on wave troughs. The mechanisms range from capillary ripples on wave crests to larger scale wave breaking. Ambient swell and non-uniform currents can also cause significant spatial variations of the surface roughness as short waves become steeper on the swell crest than those on the swell trough. This study parameterizes the spatial variability of the sea surface roughness and quantifies the resultant variations of momentum and energy exchanges between the atmosphere and the coastal ocean using a phase-resolving numerical wave model. These results have been presented at conferences and submitted to a journal for possible publication. This report is organized as follows. First, the author presents the new parameterization of the momentum flux transferred from the wind to surface gravity waves in the coastal zone. Next, he analyzes the effect of wave nonlinearity on the drag coefficient using Stokes' second-order wave theory. Then he shows how to implement the parameterized wind stress into the phase resolving Boussinesq wave model with enhanced dispersion properties. After that, tests of the extended Boussinesq model with the wind forcing against wave measurements in a shallow lake were carried out followed by an application of the model to the study of sea-swell interactions. The report ends with a summary of the findings. (5 figures, 28 refs.)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2003
- Accession Number
- ADA417971
Entities
People
- Quin J. Chen
Organizations
- University of South Alabama