11Cooling Summer Daytime Temperatures Cooling Summer Daytime Temperatures in Coastal California During 1948in Coastal California During 1948--2005:2005:Observations, Modeling, and ImplicationsObservations, Modeling, and ImplicationsProf. Robert BornsteinProf. Robert Bornstein, Dept. of Meteorology, Dept. of MeteorologySan Jose State UniversitySan Jose State UniversityProf. Jorge Gonzalez and Prof. Jorge Gonzalez and BereketBereketLebassiLebassi, , Dept. of Mechanical Engineering, Santa Clara U. Dept. of Mechanical Engineering, Santa Clara U. Dr. Dr. HaiderHaiderTahaTaha, Altostratus Inc., Martinez, CA, Altostratus Inc., Martinez, CAProf. Paul SwitzerProf. Paul Switzer, Dept. of Statistics, Stanford U., Dept. of Statistics, Stanford U.Dr. Robert Van BuskirkDr. Robert Van Buskirk, Energy Efficiency Standards Group, , Energy Efficiency Standards Group, LBNL, Berkeley, CALBNL, Berkeley, CAPresented at thePresented at theChairChair’’s Air Pollution Seminar,s Air Pollution Seminar,CARBCARB19 August 200819 August 200822OutlineOutline••Introduction toIntroduction toresearchresearch••teamteam••topictopic••Our Coastal cooling: Our Coastal cooling: observationsobservations••Our CA modeling studies forOur CA modeling studies for••mesoscale meteorologymesoscale meteorology••urban heat islands (UHIs)urban heat islands (UHIs)••regional air qualityregional air quality••climate changeclimate change••Needed future effortsNeeded future efforts••determination of coastaldetermination of coastal--cooling impactscooling impacts••use of mesoscale met modelinguse of mesoscale met modeling33Research TeamResearch Team’’s Expertise s Expertise San Jose State U.:San Jose State U.:mesomeso--met observations met observations and modelingand modelingSanta Clara U.:Santa Clara U.:sustainable development; sustainable development; GIS; and climate change downscaling & GIS; and climate change downscaling & analysisanalysisAltostratus Inc.:Altostratus Inc.:linked mesoscale modeling linked mesoscale modeling for urban heat island (UHI) & regional ozonefor urban heat island (UHI) & regional ozoneStanford U.:Stanford U.:statistical evaluation of environstatistical evaluation of environ--mental datamental dataLBNL:LBNL:energyenergy--usage trendusage trend--analysis analysis44The researchThe research--problemproblemWhat are the impacts of global climate change on CAWhat are the impacts of global climate change on CA––climate, e.g., seasonal and daily temperature trendsclimate, e.g., seasonal and daily temperature trends––weather, e.g., precipitation and water supplyweather, e.g., precipitation and water supply––air quality, e.g., air quality, e.g., ozone and PMozone and PM––energy planning, e.g., for peak usageenergy planning, e.g., for peak usage––human health, e.g., UHI and thermal stress levelshuman health, e.g., UHI and thermal stress levels––agriculture, e.g., winery operationsagriculture, e.g., winery operationsHow can mesoscale modeling best be used in CA to:How can mesoscale modeling best be used in CA to:––reproduce past changes reproduce past changes ––estimate future trends estimate future trends55BackgroundBackgroundGlobal scale observations Global scale observations generallygenerallyshow past show past asymmetric (more for asymmetric (more for TTminminthan for than for TTmaxmax) warming ) warming accelerated since midaccelerated since mid--1970s on1970s on––global scale (1.0global scale (1.0--2.5 deg resolution) 2.5 deg resolution) (see graph)(see graph)––regional scales regional scales GlobalGlobal--model results model results ––match the observationsmatch the observations––predict accelerated further warming predict accelerated further warming CA downscaledCA downscaledglobalglobal--model results model results (see graph)(see graph)––have been done (at SCU & elsewhere) onto 10have been done (at SCU & elsewhere) onto 10--km grids km grids ––show summer warming that decreases towards coastshow summer warming that decreases towards coast66Not much change from mid-40s to mid-70s, when valuesstarted to again rapidly rise77Statistically downStatistically down--scaled (Prof. Maurer, SCU) 1950scaled (Prof. Maurer, SCU) 1950--2000 2000 modeled annual summer (JJA) temps (modeled annual summer (JJA) temps (OOC) show C) show warming rates that decrease towards coastwarming rates that decrease towards coast88Earlier climateEarlier climate--change (* = for CA) studies have change (* = for CA) studies have disdis--cussed climatecussed climate--change impacts in terms of increased:change impacts in terms of increased:SSTs & urbanization SSTs & urbanization (*Goodridge (*Goodridge ‘‘9191, Karl et al. , Karl et al. ‘‘93 )93 )Cloud cover Cloud cover (*(*Nemani et al. 2001Nemani et al. 2001))Coastal upwelling Coastal upwelling (*(*BakumBakum19901990;;SnyderSnyderet al. 2003; et al. 2003; McGregor et al. 2007)McGregor et al. 2007)LandLand--cover conversions (Chase et al. 2000; cover conversions (Chase et al. 2000; MintzMintz1984; Zhang 1997) 1984; Zhang 1997) Irrigation Irrigation (*Christy et al. (*Christy et al. ‘‘0606; Kueppers et al. ; Kueppers et al. ’’07, 07, BonfilsBonfils& Duffy & Duffy ’’07, 07, **LobellLobell& & BonfilsBonfilset al. et al. ‘‘0808) ) Solar absorption (Solar absorption (StenchikovStenchikov& & RobockRobock1995) 1995)99The Current HypothesisThe Current HypothesisIncreasedIncreasedGHGGHG--induced induced inland tempsinland tempsÆÆIncreased (Coast To Inland) Increased (Coast To Inland) pressure & temp pressure & temp gradientsgradientsÆÆIncreased Increased sea breezesea breezefreq, freq, intensity, penetration, &/or intensity, penetration, &/or duration duration ÆÆCoastal areas should show Coastal areas should show cooling summer daytime max cooling summer daytime max tempstemps(i.e., a reverse (i.e., a reverse reaction)reaction)Note:Note:Not a totally original idea Not a totally original idea ÆÆ1010CURRENT DATACURRENT DATANCDC Daily Max & Min 2NCDC Daily Max & Min 2--meter Tempsmeter Temps––From about 300 CA NWS COOP Sites (see map) From about 300 CA NWS COOP Sites (see map) ––For 1948For 1948--20052005––Have been used in many other CA climateHave been used in many other CA climate--change