简介：TheaimofthisworkisanimprovementoftheparameterizationofthesoilmoistureintheschemeoftheLandSurfaceProcessModel(LSPM)forapplicationsoverdesertareas.Infact,inverydryconditions,thewatervapourfluxplaysanimportantroleintheevaporationprocessesandinfluencestheundergroundprofilesofhumidityandtemperature.TheimprovedversionofsoilmoistureparametcrizationintheLSPMschemehasbeencheckedbyusingthedatatakenfromthedatabaseofthefieldexperimentHAPEX-Sahel(Hydrology-AtmospherePilotExperimentintheSahel,1990-1992).ModelsimulationsrefertothreedifferentstationslocatedinNiger(Fallow,MilletandTigersites)whereinputdataforLSPMandobservationsweresimultaneouslyavailable.TheresultsofsimulationstakingintoaccountthewatervapourfluxinthesoilmodelLSPM,seemtocomparebetterwiththeobservedbehaviourofsoilmoistureandturbulentheatfluxesthanthoseoverlookingthewatervapourflux,confirmingthegreatimportanceofthewatervapourinsuchdryconditions.

简介：ByemployingtheimprovedT42L9spectralmodelintroducedbyNMC(Beijing)fromECMWFandutilizingtheFGGE-IIIbdatacoveringtheperiodof14—19June1979,theatmosphericresponsestotheabnormalsoilmoistureduringthemedium-rangeperiodhavebeenstudiednumerically.Accordingtotheinitialfieldat12GMT14June,afive-daynumericalexperimentunderdifferentconditionsofthesoilmoisturehasbeencarriedoutrespectively.ThemonthlymeanclimatologicalsoilmoistureforJunehasbeenusedinthecontrolexperimentintheinitialtimeanditchangeswithtimeaccordingtothemoisturebudgetequationatthelandsurface.Comparingwiththeexperimentswithdryorwetsoil.onecanconcludethat:1)Sourceofprecipitationovercontinentsinsummerconsistsoftheland-surfaceevaporationandthemoisturetransferfromoceans.Theirintensitiesarecomparableduringthemedium-rangetimescalewhenthesoilevaporatesitsmoisturesufficiently.Therefore,thesoilmoisturecaninfluencetheglobalprecipitationandthegeneralcirculationsignificantly;2)Byinfluencingthethermodynamicdifferencebetweenlandandsea,thesoilmoisturecanchangetheintensityofmonsoonandprecipitationdistribution;3)Theresponseoftheatmospheretotheabnormalsoilmoisturehasthecharacteristicsofgeographicaldistributionandnonlinearinteractions;4)Humanactivi-tiesontheworldcaninfluencetheenvironmentgreatly.

简介：Thepaperinvestigatestheabilitytoretrievethetruesoilmoistureprofilebyassimilatingnear-surfacesoilmoistureintoasoilmoisturemodelwithanensembleKalmanfilter(EnKF)assimilationscheme,includingtheeffectofensemblesize,updateintervalandnonlinearitiesintheprofileretrieval,therequiredtimeforfullretrievalofthesoilmoistureprofiles,andthepossibleinfluenceofthedepthofthesoilmoistureobservation.Thesequestionsareaddressedbyadesktopstudyusingsyntheticdata.The'true'soilmoistureprofilesaregeneratedfromthesoilmoisturemodelundertheboundaryconditionof0.5cmd-1evaporation.Totesttheassimilationschemes,themodelisinitializedwithapoorinitialguessofthesoilmoistureprofile,anddifferentensemblesizesaretestedshowingthatanensembleof40membersisenoughtorepresentthecovarianceofthemodelforecasts.Alsocomparedaretheresultswiththosefromthedirectinsertionassimilationscheme,showingthattheEnKFissuperiortothedirectinsertionassimilationscheme,forhourlyobservations,withretrievalofthesoilmoistureprofilebeingachievedin16hascomparedto12daysormore.Fordailyobservations,thetruesoilmoistureprofileisachievedinabout15dayswiththeEnKF,butitisimpossibletoapproximatethetruemoisturewithin18daysbyusingdirectinsertion.ItisalsofoundthatobservationdepthdoesnothaveasignificanteffectonprofileretrievaltimefortheEnKF.Thenonlinearitieshavesomenegativeinfluenceontheoptimalestimatesofsoilmoistureprofilebutnotveryseriously.

简介：Theatmosphericgeneralcirculationmodelcoupledtothemixedlayeroceanmodelhasbeenusedtosimulatethechangesoftheglobalsoilmoisture.Comparingthesimulatedresultswithobservations,itisshownthatthemodelisca-pableofdoingsensitiveexperimentsaboutthecarbondioxidechange.The2×CO2/1×CO2comparisonshowsthattherearetheobviouschangesofthesoilmoistureintheglobalforfourseasons.Therearethewetsoilmoistureinthelowerlatitudesofbothhemispheresanddrysoilmoistureinthemid-dlelatitudesofbothhemispheresforfourseasons.Thedrysoilmoistureinsummerandwetinotherseasonsarefoundinthenorthernhigherlatitudes.TheanalysesofthephysicalfeedbacksresponsiblefortheCO2-inducedchangesofsoilmoistureshowthatthebud-getsofthesurfacewaterandheataretheimportantfactors.