TheLouisschemeandtheCOAREalgorithm(version3.0)aretestedagainsteddycovarianceandinertialdissipationmethodsforfrictionvelocityestimatesindifferentwind-sea/swellregimes.Atmosphericforcingdata,tabulatedbyDonelanetal.(1997.JPhysOceanog,27:2087～2099),werecollectedfromamastontheforedeckofaSWATH(smallwater-planearea,twinhull)shipindeepseaofftheStateofVirginiaduringthesurfacewavedynamicsexperiment.Thesedataarerepresentativeoflowtomoderatewindregimes.TheaerodynamicroughnesslengthisdeterminedbyusingtheCharnockrelationship.TheintercomparisonshowsthattheLouisschemeandtheCOAREalgorithmunderestimatethefrictionvelocityby6%and3%respectivelyunderpurewindseaconditions,15%and13%respectivelyundercrossswellconditions,and21%and17%respectivelyundercounterswellconditions.Theanalysisshowsthattheseunderestimationswerecausedbythemethodchosentodeterminetheaerodynamicroughnesslengthbecauseitsignificantlyunderestimatestheaerodynamicroughnesslength.Itisespeciallytrueunderthecrossswellandcounterswellconditions.
