Month-long observations of along-channel velocity made close to the surface of Knight Inlet are used with a numerical model to estimate the roughness length z 0 on the water side of the air––sea interface. In analogy with a very common parameterization for z 0 on the air side of the air––sea interface, z 0 is parameterized in the numerical model as z 0 == au 2 ∗∗ / g where u ∗∗ == ( ττ / ρρ ) 1/2 is the friction velocity, g is the acceleration due to gravity, ττ is the wind stress, ρρ is the density of water, and a is an empirical constant. It is found that a ≈≈ O (10 5 ) for the dataset from Knight Inlet, a value four orders of magnitude larger than the value commonly used to estimate z 0 on the air side of the air––sea interface. When compared to empirical estimates of the significant wave height H s , it is found that z 0 ≈≈ O ( H s ). Further evidence is provided that a numerical model that uses the Mellor––Yamada level 2.5 turbulence closure scheme can simulate the near-surface, wind-forced circulation quite well.
Journal of Physical Oceanography – American Meteorological Society
Published: Nov 13, 1997