Increased aerodynamic roughness owing to surfzone foam
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Authors
MacMahan, Jamie
Subjects
Advisors
Date of Issue
2017-08
Date
Publisher
American Meteorological Society (AMS)
Language
Abstract
Drag coefficients Cd obtained through direct eddy covariance estimates of the wind stress were
observed at four different sandy beaches with dissipative surfzones along the coastline of Monterey
Bay, California. The measured surfzone Cd (;2 3 1023) is twice as large as open-ocean estimates and
consistent with recent estimates of Cd over the surfzone and shoaling region. Owing to the
heterogeneous nature of the near shore consisting of nonbreaking shoaling waves and breaking
surfzone waves, the surfzone wind stress source region is estimated from the footprint probability
distribution derived for stable and unstable atmospheric conditions. An empirical model developed
for estimating the Cd for open-ocean foam coverage dependent on wind speed is modified for foam
coverage owing to depth-limited wave breaking within the surfzone. A modified empirical Cd model
for surfzone foam predicts similar values as the measured Cd and provides an alternative mechanism
to describe roughness.
Type
Article
Description
The article of record as published may be found at http://dx.doi.org/10.1175/JPO-D-17-0054.1
Series/Report No
Department
Oceanography
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
ONR Coastal Land Sea Air Interaction (CLASI) pilot experiment
Funding
ONR Grant N0001416WX01116
Format
8 p.
Citation
J. McMahan, "Increased aerodynamic roughness owing to surfzone foam," Journal of Physical Oceanography, v.47, (August 2017), pp. 2115-2122.
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.