Ocean Observing and Climate
OVAC Theme 2 - Improved Flux Parameterisations
The aerodynamic roughness of the sea surface may be represented
by the Drag coefficient CD10n or the roughness length z0. It
modulates all the air-sea fluxes including wind stress, heat,
water vapour and the biogeochemical gases.
Many researchers have attempted to parameterise the roughness in terms of the "wave age", which is the ratio of the wave velocity (Cp) to either the wind velocity (U10n) or the wind stress (U*2) - equation 1.
We have shown that equation 2, which parameterises z0 in terms of the height (Hs) and steepness (Hs/Lp) of the dominant waves gives a better fit to a wide range of experimental data (Taylor and Yelland, 2001).
The new roughness formula successfully reproduces the observed roughness for data from wave flumes, lakes and coastal and open ocean regions. It predicts lower roughness in hurricane strength winds compared to previous parameterisations. However it does not predict the high roughness which has been associated with very young waves in some field observations, so further study is needed.
Links to OVAC Theme 2 Research
Rainfall Variability Atlantic Freshwater SST Anomalies Flux Parameterisations
