Accurateestimatesofalbedosarerequiredinclimatemodeling.Accurateandsimpleschemesforradiativetransferwithincanopyarerequiredfortheseestimates,butseverelimitationsexist.Thispaperdevelopedafour-streamsolarradiativetransfermodelandcoupleditwithalandsurfaceprocessmodel.Theradiativemodelusesafour-streamapproximationmethodasintheatmospheretoobtainanalyticsolutionsofthebasicequationofcanopyradiativetransfer.Asananalyticalmodel,thefour-streamradiativetransfermodelcanbeeasilyappliedefficientlytoimprovetheparameterizationoflandsurfaceradiationinclimatemodels.Ourfour-streamsolarradiativetransfermodelisbasedonatwo-streamshortwaveradiativetransfermodel.Itcansimulateshortwavesolarradiativetransferwithincanopyaccordingtotherelevanttheoryintheatmosphere.Eachparameterofthebasicradiativetransferequationofcanopyhasspecialgeometryandopticalcharactersofleavesorcanopy.Theupwardordownwardradiativefluxesarerelatedtothediffusephasefunction,theG-function,leafreflectivityandtransmission,leafareaindex,andthesolarangleoftheincidentbeam.Thefour-streamsimulationiscomparedwiththatofthetwo-streammodel.Thefour-streammodelisprovedsuccessfulthroughitsconsistentmodelingofcanopyalbedoatanysolarincidentangle.Inordertocompareandfinddifferencesbetweentheresultspredictedbythefour-andtwo-streammodels,anumberofnumericalexperimentsareperformedthroughexaminingtheeffectsofdifferentleafareaindices,leafangledistributions,opticalpropertiesofleaves,andgroundsurfaceconditionsonthecanopyalbedo.Parallelexperimentsshowthatthecanopyalbedospredictedbythetwomodelsdiffersignificantlywhentheleafangledistributionissphericalandvertical.Theresultsalsoshowthatthedifferenceisparticularlygreatfordifferentincidentsolarbeams.OneadditionalexperimentiscarriedouttoevaluatethesimulationsoftheBATSla
