On the added value of coupled wind-wave-current modeling : revised version

A. Sterl, Ministry of Infrastructure and Water Management, Royal Netherlands Meteorological Institute (KNMI)
De Bilt : KNMI

Atmosphere (wind), hydrography (water level and currents) and waves influence each other. Published evidence indicates that taking these feedbacks into account by using coupled models improves model performance. It appears that in the open sea the coupling between atmosphere and waves has the largest coupling effects. This coupling accounts for the fact that the stress is sea-state dependent, with younger and steeper waves extracting more momentum from the atmosphere than older and smoother waves. The net effect is a reduction of the wind speed of the order of 10% under storm conditions. The results disagree on the effect on wave heights. The effects are large-scale, but the impact on wave heights seems to vanish in shallow water. Unfortunately, none of the reviewed papers investigate the impact of the wind changes on water levels, nor do they report on changes in wind stress, which could be used to estimate the effects on water levels. The vertical momentum flux (stress) from the atmosphere primarily goes into the wave field, from where the largest part is directly released to the currents. A small part of the momentum is transported by the waves and released near the coast. The effect of this release on the water levels needs to be investigated.

31 p.
(Technical report = Technisch rapport ; TR-365)
With ref.