Avariationaltechnique(VT)isappliedtoestimatesurfacesensibleandlatentheatfluxesbasedonobservationsofairtemperature,windspeed,andhumidity,respectively,atthreeheights(1m,4m,and10m),andthesurfaceenergyandradiationbudgetsbythesurfaceenergyandradiationsystem(SERBS).Themethodfullyusesallinformationprovidedbythemeasurementsofairtemperature,wind,andhumidityprofiles,thesurfaceenergybudget,andthesimilarityprofileformulaeaswell.DatacollectedatFeixiexperimentstationinstalledbytheChinaHeavyRainExperimentandStudy(HeRES)Programareusedtotestthemethod.Resultsshowthattheproposedtechniquecanovercomethewell-knownunstablilityproblemthatoccurswhentheBowenmethodbecomessingular;incomparisonwiththeprofilemethod,itreducesboththesensitivitiesoflatentheatfluxestoobservationalerrorsinhumidityandthoseofsensibleheatfluxestoobservationalerrorsintemperature,whiletheestimatedheatfluxesapproximatelysatisfythesurfaceenergybudget.Therefore,thevariationaltechniqueismorereliableandstablethanthetwoconventionalmethodsinestimatingsurfacesensibleandlatentheatfluxes.
