ISPRSJournalofPhotogrammetryandRemoteSensing67(2011)65–72 ContentslistsavailableatSciVerseScienceDirect ISPRS Journal of Photogrammetry and Remote Sensing journal homepage: www.elsevier.com/locate/isprsjprs Estimation of the relationship between remotely sensed anthropogenic heat discharge and building energy use Yuyu Zhoua,⇑, Qihao Wengb, Kevin R. Gurneyc, Yanmin Shuaid,e, Xuefei Huf aJointGlobalChangeResearchInstitute,PacificNorthwestNationalLaboratory,5825UniversityResearchCourt,Suite3500,CollegePark,MD20740,USA bCenterforUrbanandEnvironmentalChange,DepartmentofEarthandEnvironmentalSystems,IndianaStateUniversity,TerreHaute,IN47809,USA cSchoolofLifeSciences,ArizonaStateUniversity,P.O.Box874501,Tempe,AZ85287-4501,USA dEarthResourcesTechnologyInc.,Laurel,MD20707,USA eNASAGoddardSpaceFlightCenter,Greenbelt,MD20771,USA fRollinsSchoolofPublicHealth,EmoryUniversity,Atlanta,GA30322,USA a r t i c l e i n f o a b s t r a c t Articlehistory: Thispaperexaminedtherelationshipbetweenremotelysensedanthropogenicheatdischargeandenergy Received30May2011 usefromresidentialandcommercialbuildingsacrossmultiplescalesinthecityofIndianapolis,Indiana, Receivedinrevisedform19August2011 USA.Theanthropogenicheatdischargewasestimatedwitharemotesensing-basedsurfaceenergybal- Accepted17October2011 ancemodel,whichwasparameterizedusinglandcover,landsurfacetemperature,albedo,andmeteoro- Availableonlinexxxx logicaldata.ThebuildingenergyusewasestimatedusingaGIS-basedbuildingenergysimulationmodel inconjunctionwithDepartmentofEnergy/EnergyInformationAdministrationsurveydata,theAssessor’s Keywords: parceldata,GISfloorareasdata,andremotesensing-derivedbuildingheightdata.Thespatialpatternsof Anthropogenicheatdischarge anthropogenicheatdischargeandenergyusefromresidentialandcommercialbuildingswereanalyzed Buildingenergyuse andcompared.Quantitativerelationshipswereevaluatedacrossmultiplescalesfrompixelaggregationto Multi-scale Urbanheatisland censusblock.Theresultsindicatethatanthropogenicheatdischargeisconsistentwithbuildingenergy Urbanremotesensing useintermsofthespatialpattern,andthatbuildingenergyuseaccountsforasignificantfractionof anthropogenic heat discharge. Theresearch also implies thatthe relationshipbetween anthropogenic heatdischargeandbuildingenergyuseisscale-dependent.Thesimultaneousestimationofanthropo- genicheatdischargeandbuildingenergyuseviatwoindependentmethodsimprovestheunderstanding of the surface energy balance in anurban landscape. The anthropogenic heat discharge derived from remotesensingandmeteorologicaldata may beableto serveas aspatial distribution proxy forspa- tially-resolved building energy use, and even for fossil-fuel CO emissions if additional factors are 2 considered. (cid:2)2011InternationalSocietyforPhotogrammetryandRemoteSensing,Inc.(ISPRS)Allrightsreserved. 1.Introduction pacts on the urban environment, a key issue in global environ- mental change. The urban heat island (UHI) phenomenon is formed when Themethodsusedtoestimateanthropogenicheatdischargecan higher atmospheric and surface temperatures in urbanized areas be grouped into three major categories: inventory approaches, are observed over the surrounding rural areas (Voogt and Oke, micrometeorologically-basedenergybudgetclosuremethods,and 2003).Basedonthesurfaceenergybalancetheory,UHIismainly buildingenergymodelingapproaches(Sailor,2011).Forexample, caused by the combination of anthropogenic heat discharge due usingainventoryapproachLeeetal.estimatedanthropogenicheat to energy consumption, increased impervious surface area, and emissionsintheGyeong-InregionofKoreain2002basedontheen- decreased vegetation and water area (Kato and Yamaguchi, ergyconsumptionstatisticsdata(Leeetal.,2009).KatoandYamag- 2005).Humaninducedenergydischargehasanimportantimpact uchi separated the contribution of anthropogenic heat discharge ontheurbanenvironmentintermsofthesurfaceenergybalance. andheatradiationduetosolarinputtothesensibleheatfluxby Quantification of each heat flux in the energy balance, especially using an energy balance method (Kato and Yamaguchi, 2005). the human induced anthropogenic heat discharge and its spatial HeipleandSailor(2008)estimatedthehourlyenergyconsumption pattern,isimportanttoimprovetheunderstandingofhumanim- fromresidentialandcommercialbuildingsat100mspatialresolu- tioninHouston,Texasusingthebuildingenergymodelingmethod. ⇑ Eachofthesemethodshasitsstrengthsandlimitations.Estimation Correspondingauthor.Tel.:+14017891497. E-mailaddress:[email protected](Y.Zhou). of anthropogenic heat emissions using the inventory approach is 0924-2716/$-seefrontmatter(cid:2)2011InternationalSocietyforPhotogrammetryandRemoteSensing,Inc.(ISPRS)Allrightsreserved. doi:10.1016/j.isprsjprs.2011.10.007 66 Y.Zhouetal./ISPRSJournalofPhotogrammetryandRemoteSensing67(2011)65–72 basedontherealenergyconsumptiondataatthespatialscaleof utility service territories (Ichinose et al., 1999; Klysik, 1996; Lee etal.,2009;SailorandLu,2004;Taha,1997).Itisdifficulttoquan- tify thespatial distributionofenergy consumption atfine spatial and temporal scales. Spatial and temporal downscaling can only beachievedwhenadditionaldatasuchaslanduseareemployed. Energybalancemethodhasbeenappliedtoestimateenergyfluxes inurbanareasfromsiteandneighborhoodscaletocityscale(Belan etal.,2009;Massonetal.,2002;Oke,1988;Okeetal.,1999;Pigeon etal.,2007;Pigeonetal.,2008).Highspatialresolutionanthropo- genicheatdischargecanbeestimatedbasedonmicrometeorolog- ically-based energy budget closure method by the combined use of remote sensing and meteorological data (Bastiaanssen et al., 1998a,b; French et al., 2005; Kato and Yamaguchi, 2005; Kato etal.,2008;Schmuggeetal.,1998;vanderKwastetal.,2009).How- ever,astheestimationofanthropogenicheatdischargeisbasedon the residual of other components in the surface energy balance, eachcomponentintroducesuncertaintiesandpropagateserrorsto- wardthefinalestimatedanthropogenicheatflux.Byintegratingthe geospatial data and simulated temporal pattern of energy con- sumptionfor representativebuildings, energy consumption in all buildings can be estimated using the building energy modeling method (Heiple and Sailor, 2008; Ichinose et al., 1999; Zhou and Gurney,2010).However,therepresentativebuildingsmaynotbe easily categorized and the use of representative buildings may Fig.1. ThestudyareaofIndianapolisCity,MarionCounty,Indiana,USA. introduce biasin the estimationof spatial and temporalpatterns ofenergyuseforsomebuildingsasthesebuildingsmayhavediffer- FallCreek,nearthecenterofthestate.Itpresentlyextendsintonine ent behaviors of energy consumption in terms of magnitude and MarionCountyTownships,includingPike,Washington,Lawrence, temporalpatterncomparedtotherepresentativebuildings. Wayne, Center, Warren, Decatur, Perry and Franklin. The city is Althoughanthropogenicheatdischargewasstudiedusingdiffer- locatedonaflatplainandisrelativelysymmetrical,havingpossibil- ent methods in previous studies, there was limited research for itiesofexpansioninalldirections,andthecitycenterhasexpanded cross-examinationofthespatialpatternofanthropogenicheatdis- into adjacent agricultural and rural lands through encroachment charge.Eventhoughpreviousstudieshaveprovidedinsightsinto (WengandHu,2008).Indianapolisisahighlyurbanizedcitywith thehumanimpactsontheurbanenvironmentdirectlyorindirectly, spatiallyheterogeneoushumanactivities,whichservesasanideal simultaneous estimation of anthropogenic heat discharge using areaforthepurposeofthisstudy. multiplemethodswillhelptoreducetheuncertaintiesinthestudy ofurbanheatfluxesandimprovetheunderstandingoftheroleofhu- 2.2.Datasets manactivitiesinthesurfaceenergybalanceanditscontributionto UHI.Thisstudyaimstoimprovetheunderstandingoftheurbansur- AnthropogenicheatdischargeatnoontimeonJune16th,2001 faceenergybalanceandclarifythespatialpatternofenergyrelated (Saturday)wasestimatedusingasurfaceenergybalancemodeling humanactivitieswiththehelpofremotesensingdata,technologies approach(Fig.2).Thedetailsoftheapproachwerediscussedinthe andbuildingenergysimulationinahighlyurbanizedarea.Specifi- methodology section. The major data used in the energy balance cally,anthropogenicheatdischargeandenergyusefromresidential method include meteorological data, land cover, albedo and land and commercial buildings were investigated using two different surfacetemperature(LST).Impervioussurfacearea(ISA)wasalso methods in the metropolitan Indianapolis, Indiana region. First, developed and utilized as a mask in the analysis. Meteorological anthropogenicheatdischargewasestimatedusingasurfaceenergy data including air temperature, shortwave radiation, and wind balancemethod.Thenenergyusefromresidentialandcommercial speed at noon time on June 16th, 2001 were retrieved from 3- buildingswascalculatedusingabuildingenergymodelingmethod. hourlyMAT3FXCHMdataproductattheModelingandAssimilation Finally, the relationship between remotely sensed anthropogenic DataandInformationServicesCenter(http://disc.sci.gsfc.nasa.gov/ heatdischargeandbuildingenergyusewasexaminedacrossmulti- MDISC/).Thedataprocessingoflandcover,albedo,LSTandISAis plescalesfrompixelaggregationstocensusblockgroups. discussedbelowindetails. LandcoverdatafromUSGeologicalSurveyNationalLandCover 2.Studyareaanddatasets Dataset(NLCD)2001werecollectedtoretrieveparametersforthe estimationofsurfaceheatfluxes(Fig.3a).Thelandcoverclassifica- 2.1.Studyarea tionwasachievedbyusingaclassificationanddecisiontreemethod withLandsatimageryandancillarydata(Homeretal.,2004).Main Inthisstudy,Indianapolis/MarionCounty,Indianawaschosenas landcovertypesinthestudyareaincludeopenwater,urban,ever- theexperimentarea(Fig.1).IndianapolisisthecapitaloftheStateof greenforest,deciduousforest,shrub,grassland,croplandandwet- Indiana,andwaslistedasthe14thlargestcityintheUSAin2008, land.UrbanisthedominantlanduseinIndianapolisandaccounts with a population of 798,382 (US Census Bureau, 2009). The city formorethan3/4ofthetotalarea.Thisdatasetwasutilizedtocreate hasatemperateclimatewithoutpronouncedwetordryseasons, alookuptablebetweenlandcovertypeandmodelingparameters, buthasobviousseasonalchanges.Thetotalannualheatingdegree including coefficient for ground heat flux, roughness length and day value is 5521F, and the cooling degree day value is 1042F emissivity, which were developed in previous studies (Kato and (NationalWeatherService,2002).Thesynopticweathercondition Yamaguchi,2005;Katoetal.,2008;Snyderetal.,1998).Landcover during the study period is typical of mid-latitude summer time. basedparametersusedintheestimationofheatfluxeswillbefur- ThecityofIndianapolisliesontheWhiteRiveratitsconfluencewith therdiscussedinthemethodologysection. Y.Zhouetal./ISPRSJournalofPhotogrammetryandRemoteSensing67(2011)65–72 67 Fig.2. Methodologyusedtoestimateanthropogenicheatdischargeandenergyusefromresidentialandcommercialbuildings. Fig.3. ModelinputdatainthestudyareaofIndianapolisincludinglandcover(a),LST(b),albedo(c),andISA(d). Theadvancedspacebornethermalemissionandreflectionradi- NASA(Fig.3b).ThealgorithmforconvertingASTERthermalinfra- ometer (ASTER) on-demand L2 surface kinetic temperature data redmeasurementstoLSTshasbeenreportedbytheASTERtemper- with 90m resolution of June 16th, 2001 were purchased from ature/emissivityworkinggroup(Gillespieetal.,1999),withwhich 68 Y.Zhouetal./ISPRSJournalofPhotogrammetryandRemoteSensing67(2011)65–72 surfacekinetictemperaturewasdeterminedbyapplyingPlanck’s Yamaguchi, 2005; Kato et al., 2008; Oke, 1988; Xu et al., 2008). Lawusingthe emissivityvaluesfromthetemperature-emissivity ThemethodisillustratedintheleftpanelofFig.2.Thesurfaceen- separation(TES)algorithm.LSTvaluescalculatedusingthisproce- ergybalanceduetosurfacepropertiesandanthropogenicheating dureareexpectedtohaveanabsoluteaccuracyof1–4Kandrela- inthenear-surfaceinanurbanareacanbeexpressedasfollows: tiveaccuracyof0.3K,andsurfaceemissivityvaluesareexpectedto Q ¼HþLEþG(cid:2)R ð1Þ have an absolute accuracy of 0.05–0.1 and relative accuracy of f n 0.005(Gillespieetal.,1999). whereQ istheanthropogenicheatdischarge(Wm(cid:2)2),Histhesen- f Landsurfacealbedomapin30mspatialresolutionwasgener- sibleheat(Wm(cid:2)2),LEisthelatentheatflux(Wm(cid:2)2),andGisthe atedfromLandsatsurfacereflectanceandanisotropyinformation ground heat flux (Wm(cid:2)2), and R is the net radiation (Wm(cid:2)2). n basedonconcurrentmoderateresolutionimagingspectroradiom- Basedonthesurfaceenergybalancemodel,anthropogenicheatdis- eter(MODIS)500mobservationsthroughthealgorithmdeveloped chargeQ canbeestimatedastheresidualterm. f byShuaietal.(2011)(Fig.3c).Thelevel1Landsat7enhancedthe- In the energy balance equation, net radiation (R ) is the sum n maticmapperplus(ETM+)imagecollectedonJuly11th,2001with of short and long wave radiation at the land surface (Kato and goodqualitywas firstconvertedto30mlandsurface reflectance Yamaguchi,2005).Itiscalculatedas through Landsat ecosystem disturbance adaptive processing sys- R ¼ð1(cid:2)aÞR þe eR (cid:2)eR ð2Þ tem,anautomaticcalibrationandatmosphericcorrectionprocess n S a d u (Maseketal.,2006).Thentheclassification-based 500mBidirec- where R is the shortwave radiation (Wm(cid:2)2) which is retrieved s tional reflectance distribution function (BRDFs) for the homoge- fromthemeteorologicaldata.aisthesurfacealbedowhichisde- nous area were extracted from the concurrent MODIS BRDF rivedfromtheremotesensingdata,andthecreationof30mspatial product (Schaaf et al., 2002) with the highest inversion quality resolutionalbedodataisdiscussedinthedatasection.eisthesur- (Shuai et al., 2008), followed by the calculation of spectral albe- faceemissivity,anditisdeterminedbasedonlandtypefromNLCD do-to-reflectance ratios for each class at the MODIS pixel scale. landcoverdata(Snyderetal.,1998).e istheatmosphericemissiv- a Next,thespectralLandsatalbedoswereinversedbyapplyingthese ity,anditisestimatedusinganempiricalequationusedbyKatoand ratiosintoLandsatsurfacereflectance.Accordingtothevalidation Yamaguchi(2005) with ground measurements, the Landsat albedo meets the accu- (cid:2) (cid:3) racy required by regional climate modeling. Compared with the e ¼1:24 ea 1=7 ð3Þ MODIS500mproducts,italsoprovidesadetailedlandscapetex- a Ta ture and improved accuracy at the validation stations (Shuai whereT is the atmospherictemperature (K) from meteorological etal.,2011).Itwasassumedthattherewasnosignificantchange a data,ande istheatmosphericwatervaporpressure(hPa),which ofalbedobetweenJune16thandJuly11th,2001. a isestimatedusingthemethodbyAllenetal.(1998) ISAwasestimatedonJune16th,2001usingthemethoddevel- opedbyWengetal.(2009)(Fig.3d).Throughthismethod,imper- RH e(cid:3)ðT Þþe(cid:3)ðT Þ e ¼ mean min max ð4Þ vious surface was calculated based on the relationship between a 100 2 the reflectance of two endmembers (high- and low-albedo) and wheree(cid:3)(T ) is the saturationvapor pressure at daily minimum the reflectance of the impervious areas. By examining the rela- min temperature(hPa),e(cid:3)(T )isthesaturationvaporpressureatdaily tionships between impervious surfaces and four endmembers, it max maximum temperature (hPa), and RH is the mean relative isfoundthatimpervioussurfaceswerelocatedonorneartheline mean humidity(%). connectingthe low- and high-albedo endmembers in the feature R andR usedtocalculatenetradiation(R )arethedownward space.Anestimationprocedurewasthusdevelopedbasedonthis anddupwardublackbodyradiation(Wm(cid:2)2),andntheyarecalculated relationship by adding the fractions of high- and low-albedo usingthefollowingequations(Xuetal.,2008) endmembers. Energyusefromcommercialandresidentialbuildingswasesti- R ¼rT4 ð5Þ d a matedusingabuildingenergysimulationmethod(rightpanelof R ¼rT4 ð6Þ Fig.2).Inthismethod,thesimulationofbuildingenergyusewas u s drivenbythetypicalmeteorologicalyeardata.Baseondataavail- whereristheStefan–Boltzmannconstant(5.67E(cid:2)08Wm(cid:2)2K(cid:2)4), abilitynoontimeofJune15th,2002(Saturday)waschosentorep- andT isthesurfacekinetictemperature(K).Theprocesstoderive s resent building energy use for the typical weekend during the thesurfacetemperaturewasdiscussedinthedatasection. summertimetobecomparabletotheremotelysensedanthropo- Sensibleheatflux(H)isestimatedbasedonthefollowingequa- logic heat discharge. The major data used in the building energy tion (Allen et al., 1998; Kato and Yamaguchi, 2005; Kato et al., modelingincludesaGISdatabaseofbuildingfootprints,theCounty 2008;Xuetal.,2008) Assessor’sparceldatabase,andthebuildingheightdata.AlocalGIS databaseofbuildingfootprintswascollectedandusedtoretrieve H¼qC To(cid:2)Ta ð7Þ p r thefloorareaofeachbuilding.TheCountyAssessor’sparceldata- a basewasaMicrosoftAccessbaseddataset.Itwasusedtoretrieve whereqistheairdensity(kgm(cid:2)3),C isthespecificheatofairat p thebuildingtypeandageandtolinkwiththeGISbuildingfoot- constant pressure (Jkg(cid:2)1K(cid:2)1), and T is the surface aerodynamic o print. Building heights were estimated from a remote sensing- temperature.AsT isdifficulttoobtain,remotesensingderivedsur- o baseddigitalsurfacemodelandadigitalelevationmodelandused face temperature was used to approach T (Kato et al., 2008). r o a tocalculatefloornumbersforeachbuilding. (sm(cid:2)1) is the aerodynamic resistance which is calculated using thefollowingsimplerelation(Allenetal.,1998) (cid:4) (cid:5) (cid:4) (cid:5) 3.Methodology ln zm(cid:2)d ln zh(cid:2)d r ¼ z0m z0h ð8Þ a k2u 3.1.Estimationofanthropogenicheatdischarge z wherez istheheightofwindmeasurements(m),z istheheightof m h In this study, anthropogenic heat discharge was estimated humidity measurements (m), d is the zero plane displacement based on a surface energy balance modeling method (Kato and height (m), z is the roughness length governing momentum 0m Y.Zhouetal./ISPRSJournalofPhotogrammetryandRemoteSensing67(2011)65–72 69 transfer(m),z istheroughnesslengthgoverningtransferofheat modelusingthemethodbyZhouandGurney(2010).Withthecom- 0h and vapor (m), k is the von Karman’s constant (0.4), and u is the binationofbuildingareafromGISfootprintdata,buildingtypefrom z windspeed(ms(cid:2)1)atheightzfromthemeteorologicaldata. theAssessor’sparceldata,floornumbersfrombuildingheightdata, Latentheatflux(LE)isestimatedusingthefollowingequation and electric and non-electric EUIs for building prototypes, energy (KatoandYamaguchi,2005) use in all residential and commercial buildings was estimated in LE¼qCPcðers(cid:2)þeraÞ ð9Þ thestudyarea. a s c 4.Results wheree isthesaturationvaporpressure(hPa), isthepsychromet- s ric constant (hPaK(cid:2)1), and r is the stomatal resistance (sm(cid:2)1) s 4.1.Anthropogenicheatdischarge which is estimated based on land type from the NLCD land cover data(Katoetal.,2008). The anthropogenic heat discharge in the study area at noon Groundheatflux(G)isestimatedusingthefollowingempirical timeonJune16th,2001wasestimatedusingtheenergybalance equationbyKatoandYamaguchi(2005) method.Toreducetheuncertaintiesintheevaluationofanthropo- G¼CgRn ð10Þ genic heat discharge, especially in less developed areas, ISA data wereusedtoexcludepixelswiththeISAlessthan25%.Theresult whereC is afixedcoefficient basedontheNLCDland covertype g ofanthropogenicheatdischargeestimationisshowninFig.4.The andseason(KatoandYamaguchi,2005). resultshowsthespatialpatternandmagnitudeofanthropogenic heatdischargeintheCityofIndianapolisinatypicalsummertime. 3.2.Estimationofenergyusefromresidentialandcommercial The anthropogenic heat discharge ranges from 0 to 400Wm(cid:2)2, buildings withameanvalueof32Wm(cid:2)2.Thehighanthropogenicheatdis- chargeoccursinthedenseresidentialandcommercialareassuch Energyusefromresidentialandcommercialbuildingswasesti- asthecenterofthecityandtheresidentialareasinthenorthwest mated using a building energy modeling method, which is illus- cornerofthecity.ThetownshipofCenterhasthehighestanthro- trated in the right panel of Fig. 2. The method for CO2 emissions pogenicheatdischargeof78Wm(cid:2)2asithashighdensityofcom- quantification developed by Zhou and Gurney (2010), in which mercial buildings while the Franklin township with large rural on-sitefossil-fuelCO2emissionsfromresidentialandcommercial areasobservesthelowestvalue.Therearenegativevaluesin the buildings were quantified by downscaling the county-level com- anthropogenicheatdischargeestimation,althoughittheoretically mercial and residential fossil fuel CO2 emissions, was modified should be greater than 0Wm(cid:2)2. These negative values are re- and extended. Using the modified method energy use from resi- gardedasestimationerrors,andweresetto0Wm(cid:2)2inthefinal dentialandcommercialbuildingswasestimatedforeachbuilding. result. First, a building typology was developed to define the building typesforresidentialandcommercialbuildingstockinIndianapolis. 4.2.Buildingenergyuse Atotalof30buildingprototypes,22commercialandeightresiden- tial,weredefinedbasedonthebuildingtype,size,andagewiththe Using the building energy modeling approach, the energy use helpoftheMarionCountyAssessor’sparceldatabase. fromresidentialandcommercialbuildingsineachbuildingatnoon Second,hourlybuildingEnergyUseIntensity(EUI)–theenergy timeonJune15th,2002wasestimatedinthestudyarea.Thespa- used per unit floor area – was simulated using the Quick Energy tialdistributionoftheenergyusefromresidentialandcommercial SimulationTool(eQUEST)foreachbuildingprototype(USDepart- buildingsatare-sampled90m spatialresolutionisillustratedin mentofEnergy,2009).ThemajorparametersusedineQUESTsim- ulation including building shell characteristics (e.g., R value), internalload(e.g.,lighting)andHeating,Ventilating,andAirCon- ditioningsystemcharacteristicswerederivedfromHuangetal.for theNorthCentralUScensusregion(Huangetal.,1991).Indianap- oliswasspecifiedasthelocationineQUESTsimulationtoretrieve thetypicalweatherinformationforthisregion.TheEUIsandthe ratio of the non-electric to electric EUI values from the eQUEST simulation were calibrated using the US Department of Energy’s EnergyInformationAdministrationdatafortheEastNorthCentral Census Division from its residential energy consumption survey and commercial building energy consumption survey (US Energy InformationAdministration,2001;USEnergyInformationAdmin- istration,2003). Finally,energyuseineachbuildingwasestimatedfromthecal- ibratednon-electricandelectricEUIs,buildingareaandnumberof floorsasfollows: (cid:4) (cid:5) EbuildingðiÞ¼ EUIet;lbeuildingðiÞþEUInt;obnueilldeingðiÞ AbuildingðiÞNFbuildingðiÞ ð11Þ where EUIele is the electric energy use intensity of building t;buildingðiÞ typetforbuildingi,EUInonele isthenon-electricenergyuseinten- t;buildingðiÞ sityofbuildingtypetforbuildingi,AbuildingðiÞisthefootprintareaof buildingi(whichwasretrievedfromalocalGISdatabaseofbuilding footprints), and NFbuildingðiÞ is the number of floors for building i whichwasestimatedbasedonbuildingheightcalculatedfromare- mote sensing-based digital surface model and a digital elevation Fig.4. Thespatialdistributionofanthropogenicheatdischarge. 70 Y.Zhouetal./ISPRSJournalofPhotogrammetryandRemoteSensing67(2011)65–72 Fig.5.Tobeconsistentwiththeanthropogenicheatdischargeesti- anthropogenicheatdischargeandbuildingenergyuse.Itisworth mation,thebuildingenergyusewasexaminedwiththeexclusion noting that there are uncertainties in both datasets of anthropo- ofpixelswiththeISAlessthan25%.Theenergyusefromresidential genicheatdischargeandbuildingenergyusewhichmightcontrib- andcommercialbuildingsrangesfrom0to85Wm(cid:2)2withamean utetothediscrepancybetweenthesetwovariablestobediscussed valueof5.5Wm(cid:2)2.Thespatialvariationofbuildingenergyuseis inthenextparagraph.Theuncertaintyintheestimatedanthropo- mainlydeterminedbybuildingdensity,heightandtype.Thespatial genicheatdischargemainlycamefromeachcomponentinthesur- patternshowsthatthehighestbuildingenergyuseoccursatthecity faceenergybalance.Theinputparametersofmeteorologicaldata, center,andthatthetownshipofCenterpossessesthehighestenergy land cover, land surface temperature, and albedo may introduce useof36Wm(cid:2)2.Thebuildingenergyuseisalsohighindenseresi- theuncertaintytowardsthefinalestimationofanthropogenicheat dentialareasassociatedwithsuburbandevelopmentintheouter discharge. The uncertainty in the estimated building energy use ringofHighway465inIndianapolisasshowninFig.5. mainly came from EUIs using eQUEST simulation and building heightextractedfromadigitalsurfaceandadigitalelevationmod- el. The uncertainty analysis of fossil-fuel CO emissions which is 2 4.3.Spatialrelationship,uncertaintyandscaleeffect based on non-electric building energy use can be found in the studybyZhouandGurney(2010)usingaMonteCarloapproach. Although energy use from residential and commercial build- Theuncertaintyofnon-electricenergyuseineachtownisapprox- ings represents only one component of anthropogenic heat dis- imatelywithin10%ofthetotalenergyuse. charge, it shows an obvious consistency in terms of spatial Thediscrepancybetweenbuildingenergyuseandanthropogenic distribution with remote sensing-derived anthropogenic heat heatdischargeiscausedbyseveralfactors.First,anthropogenicheat discharge. Visual comparison between anthropogenic heat dis- dischargeincludesnotonlyenergyusefromresidentialandcom- charge (Fig. 4) and building energy use (Fig. 5) shows that they mercialbuildings,butalsoothersourcessuchasenergyusefrom both are higher in the dense residential and commercial areas industrialbuildingsandtransportation.Thequantitativerelation- and lower in the rural areas. In order to evaluate the quantita- shipconfirmsthatbuildingenergyuseaccountsforpartofanthro- tive relationship two variables were compared at pixel levels pogenic heat discharge. Second, energy use from residential and as well as at the census block level. First, the building energy commercialbuildingswasestimatedbasedonthetypicalweather use and anthropogenic heat discharge data were re-sampled to informationatnoontimeonJune15th,2002whiletheanthropo- a variety of spatial resolutions of 90m, 180m, 270m, 360m genic heat discharge was estimated at noon time on June 16th, and 450m. Furthermore, the pixels with 0.5% of the ranked 2001. The different dates of the input data may have introduced building energy use in the both ends, which are considered as inconsistencybetweentwovariables.Third,asonlylowresolution outliers,wereexcludedin the analysis. Therelationshipbetween meteorologicaldatasuchaswindspeedandairtemperatureused thesetwovariablesacrossthesescalesandtheadditionalcensus intheenergybalancemethod,thespatialvariationofimpactfrom block level is shown in Fig. 6a–f. The result indicates that the meteorologicalfactorswasnotconsideredduetodatalimitation.Fi- correlation between building energy use and anthropogenic heat nally,imageregistrationofdatausedintheestimationoftwovari- discharge is statistically significant at all spatial scales ables may also bring in uncertainties in the investigation of the (p<0.001), and that the relationship between two variables var- relationship.Itisoneofthereasonsthatthecorrelationbetween ieswithscales. Theexplainedvariance ofbuildingenergy use by anthropogenicheatdischargeandbuildingenergyusevarieswith anthropogenic heat discharge increases with the decreasing spa- thespatialresolution.Withthedecreasingspatialresolution,theer- tial resolution. rorofthespatialregistrationbetweentwoimagesdecreases.There- Apotentialapplicationofthisstudyistoreducetheuncertainty forethecorrelationbetweenbuildingenergyuseandanthropogenic inurbanenergybalancestudythroughindependentestimationof heatdischargeincreasesasindicatedbyFig.6. 5.Implications There are still challenges to obtaining accurate estimation of eachcomponentofheatfluxintheurbanenergybalancesuchas the ground heat flux. Accurate estimation of anthropogenic heat dischargewillhelptobetterunderstandtheurbanenergybalance and separate the contribution of anthropogenic heat discharge fromthatofgroundheatflux.Bycombiningwithenergyusefrom othersourcessuchasindustrialbuildingsandtransportation,the spatially-resolved energy use from residential and commercial buildings will improve the estimation of anthropogenic heat dis- charge,andtherefore,helptoreducetheuncertaintiesinthestudy ofurbanenergybalance. The relationship between building energy use and anthropo- genic heat discharge indicates that anthropogenic heat discharge may be able to serve as a spatial distribution proxy for the spa- tially-resolvedenergyuseinanurbanlandscape.Inaddition,be- cause of the relationship between energy use and fossil-fuel CO 2 emissions, anthropogenic heat discharge,which is relatively easy toobtainwiththehelpofremotelysenseddata,providesthepo- tentialtodevelopspatially-resolvedfossil-fuelCO emissionsfrom 2 building sectors with additional considerations. Together with Fig. 5. The spatial distribution of energy use from commercial and residential point source and mobile emissions, the spatially-resolved fossil- buildings. fuel CO2 emissions dataset will help to improve the scientific Y.Zhouetal./ISPRSJournalofPhotogrammetryandRemoteSensing67(2011)65–72 71 Fig.6. Therelationshipbetweenanthropogenicheatdischargeandenergyusefromresidentialandcommercialbuildingsat90m(a),180m(b),270m(c),360m(d),450m (e)spatialresolution,andtheUScensusblocklevel(f). understandingofthecontributionofhumaninducedemissionsto confirm that the energy use from residential and commercial atmosphericconcentrationthroughtransportmodelingintheur- buildings represents only partial anthropogenic heat discharge bandomain. whichincludesadditionalcomponentsofenergyusesuchasthose fromindustrialbuildingsandtransportation. Thespatialconsistencybetweenanthropogenicheatdischarge 6.Conclusions and energy use from residential and commercial buildings indi- catesthat remotelysensedanthropogenicheat dischargemay be Inthisstudy,theanthropogenicheatdischargeandenergyuse abletoserveasaspatialproxytoderivethespatialpatternofen- from residential and commercial buildings were estimated using ergyuse,andevenfossil-fuelCO2emissionswithconsiderationof twoindependentmethodssimultaneouslyintheCityofIndianap- additionalfactors.Asthespatialrelationshipbetweenbuildingen- olis in the summer time. The anthropogenic heat discharge was ergy use and anthropogenic heat discharge varies with spatial estimated using a remote sensing method, while the energy use scales,appropriatespatialresolutionshouldbeidentifiedinfuture from residential and commercial buildings was estimated with a studies to aid the development of spatially-resolved energy use GIS-based simulationmethod. The mean anthropogenic heat dis- datasets. chargeis32Wm(cid:2)2whiletheenergyusefromresidentialandcom- Theindependentestimationofbuildingenergyuseandanthro- mercial buildings is 5.5Wm(cid:2)2. The visual comparison and pogenicheatdischargewillalsohelptoimprovetheestimationof quantitative analysis show consistency between anthropogenic otherheatfluxesandtheunderstandingofenergybalanceinthe heatdischargeandbuildingenergyuseintermsofthespatialpat- urbanareas.Inordertoreducetheuncertaintiesinthestudyofur- tern and magnitude. 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