The applicability of similarity theory to a road.pdf

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1、Meteorol.Appl.6,81–88(1999)TheapplicabilityofsimilaritytheorytoaroadsurfaceDChen,TGustavssonandJBogren,DepartmentofEarthSciences,UniversityofGothenburg,40530Gothenburg,SwedenTheexistingmodelsforpredictingroadsurfacetemperatureareoftenbasedonsurfaceenergybalancewhichincludescontrib

2、utionsfromsensibleandlatentheatexchangesbetweentheatmosphereandroadsurface.Thesimilaritytheoryisusuallyappliedtocomputetheatmosphericturbulentheatfluxes.However,thetheoryonlyappliesinhorizontallyhomogeneoussituations,whichiscertainlynotthecaseforroadconditions.Aninvestigationiscarr

3、iedouttoseehowmuchmeasuredprofilesofmeanwindandtemperaturefromaroadmeteorologicalstationdeviatefromtheprofilesgivenbysimilaritytheory.Thedifferencebetweenthedataandthetheoryisrevealedbycomparingtheobservedgradientswiththetheoreticalones.Thesignoftheverticalgradientsofalldataandthere

4、lationshipsbetweentwoverticalgradientsatdifferentlevelsundernear-neutralconditionsareexamined.Itisfoundthatthemeasuredprofilesareallsystematicallydifferentfromthetheoreticalones.Thedeviationisdiscussedwithinthecontextofthepossibleexistenceofaninternalboundarylayer.Moreover,detailed

5、temperatureprofilesweremeasuredtostudythedevelopmentoftemperaturesinthefirst2.5m.Theresultsshowthatthesignofthetemperaturegradientreversesinalayerbetween0.8and1.4mandthatalargechangeintemperatureoccursinthislayer;theseeffectswereprobablycausedbylocaladvection.1.Introductionentfromit

6、ssurroundings.Ininvokingthetheory,theexistingmodelsarebasedontheassumptionthatSevereweatherconditionscausegreattrafficproblemshomogeneityisagoodapproximation.However,noespeciallyduringwinter.InseveralEuropeancountriesevidenceforthevalidityofthisapproximationforroadanetworkofstation

7、sisusedtosurveythemeteorolog-conditions,toourknowledge,hasbeengivensofar.icalconditionsalongmajorroads.ItisespeciallyThepurposeofthisstudyistotouchonthequestiontoimportantthatthesesystemsgiveaccuratemeasure-whatextentthetheorydoesnothold.Forthatpurposementsofclimatologicalparamete

8、rsandcanbeusedtowedidacasestudyus