WHOI PO

Oceanic and surface wave processes, through air-sea interaction, are 
critical for the atmosphere and an accurate description of the surface 
wind stress. This study aims to evaluate the impacts of waves by 
comparing parameterized wind stress via COARE 3.5 bulk flux algorithm in 
a fully coupled wave-ocean-atmosphere model. Sensitivity experiments are 
conducted using two different wave roughness parameterizations within 
COARE, including one that relies solely on wind speed only assuming 
wind-wave equilibrium, and another that uses spatially varying wave age 
and wave slope. These results are compared against directly measured 
wind stress, notably at the NSF OOI Pioneering Arrays mooring in the US 
East Coast region and shipboard measurements gathered during the 
ATOMIC/EUREC4A field campaign in the Northwest Tropical Atlantic Ocean. 
We found that, for sea states dominated by mature waves uncorrelated 
with local winds of moderate to strong intensity (i.e., mixed sea), the 
COARE wave-based formulation predicts significantly lower roughness 
length and surface stress, resulting in an instantaneous increase of the 
near-surface wind speed above the constant flux layer. Further 
investigation indicates that the impact of swell on roughness element is 
over-emphasized in the current version of the COARE wave-based 
formulations, especially for mixed sea states with moderate to strong 
winds. We suggest various remedies to mitigate the deficiencies in COARE 
by incorporating the missing physics, such as the misaligned wave on the 
surface drag, and using a sea-state parameter that more robustly 
characterizes the mixed seas, such as spectrally-averaged wave phase 
speed rather than the peak wave speed that is currently used in the 
algorithm. The results of these sensitivity experiments against 
available observations will be discussed.