1 Cooling Summer Daytime Temperatures in Coastal California During 1948-2005: Observations and Implications for Energy Demand Prof. Robert Bornstein, Dept.

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Cooling Summer Daytime Temperatures Cooling Summer Daytime Temperatures in Coastal California During 1948-2005:in Coastal California During 1948-2005:

Observations and Implications for Energy Observations and Implications for Energy DemandDemand

Prof. Robert BornsteinProf. Robert Bornstein, Dept. of Meteorology, Dept. of Meteorology

San Jose State UniversitySan Jose State University

[email protected]@hotmail.comProf. Jorge Gonzalez and Bereket Lebassi, Prof. Jorge Gonzalez and Bereket Lebassi,

Dept. of Mechanical Engineering, Santa Clara U. Dept. of Mechanical Engineering, Santa Clara U.

Dr. Haider TahaDr. Haider Taha, Altostratus Inc., Martinez, CA, Altostratus Inc., Martinez, CAProf. Paul SwitzerProf. Paul Switzer, Dept. of Statistics, Stanford U., Dept. of Statistics, Stanford U.

Presented as thePresented as the5th CEC Climate Change Conference 5th CEC Climate Change Conference

8 Sept. 20088 Sept. 2008

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OutlineOutline

• Introduction toIntroduction to researchresearch• teamteam• topictopic

• Our coastal cooling analysesOur coastal cooling analyses• TrendsTrends• Spatial patternsSpatial patterns

• Needed future efforts reNeeded future efforts re• extended analysesextended analyses• downscaled modelingdownscaled modeling• coastal-cooling impactscoastal-cooling impacts

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BackgroundBackground• Global & CA observations Global & CA observations generallygenerally show show

– asymmetric (more for Tasymmetric (more for Tminmin than for T than for Tmaxmax) ) warmingwarming

– that has accelerated since mid-1970s that has accelerated since mid-1970s (see (see graph)graph)

• CA downscaledCA downscaled global-modeling global-modeling (see (see graph)graph) – has been done (at SCU & elsewhere) onto 10 has been done (at SCU & elsewhere) onto 10

km grids km grids – show summer warming that decreases towards show summer warming that decreases towards

coast coast (but no coastal cooling)(but no coastal cooling)

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Not much change from mid-40s to mid-70s, when valuesstarted to again rapidly rise

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Statistically down-scaled (Prof. Maurer, SCU) 1950-2000 Statistically down-scaled (Prof. Maurer, SCU) 1950-2000 annual summer (JJA) temp-changes (annual summer (JJA) temp-changes (00C) show warming C) show warming rates that decrease towards coast, where red dots are rates that decrease towards coast, where red dots are

COOP sites used in present study & boxes are study sub-COOP sites used in present study & boxes are study sub-areasareas

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Climate-change (*=for CA) studies (next 2 Climate-change (*=for CA) studies (next 2 slides) have discussed obs in terms of slides) have discussed obs in terms of

increased:increased:

• SSTs & urbanization SSTs & urbanization (*Goodridge ‘91(*Goodridge ‘91, Karl et al. , Karl et al. ‘93 )‘93 )

• Cloud cover Cloud cover (*(*Nemani et al. 2001Nemani et al. 2001))

• Coastal upwelling Coastal upwelling (*(*Bakum 1990Bakum 1990;; SnyderSnyder et al. et al. 2003; 2003; McGregor et al. 2007)McGregor et al. 2007)

• Land-cover conversions (Chase et al. 2000; Mintz Land-cover conversions (Chase et al. 2000; Mintz 1984; Zhang 1997) 1984; Zhang 1997)

• Irrigation Irrigation (*Christy et al. ‘06(*Christy et al. ‘06; Kueppers et al. ’07, ; Kueppers et al. ’07, Bonfils & Duffy ’07, Bonfils & Duffy ’07, *Lobell & Bonfils et al. ‘08*Lobell & Bonfils et al. ‘08) )

• Solar absorption (Solar absorption (Stenchikov & Robock 1995) Stenchikov & Robock 1995)

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Publication Parameter Studied Finding

Goodridge (1991)

80 years of annual-average daily Tave

at 112 site

Warming in both coastal (attributed to warming SSTs) & inland urban (attributed to UHI effects) areas; cooling in inland rural areas was unexplained

Nemani et al. (2001)

Sites in Napa & Son-oma Valleys during 1951-97 for Tmin & Tmax

Tmin increased & Tmax slightly

decreased, both attributed to measured increased cloud cover. Increased annual coastal TD

related to increased SSTs

Duffy et al. (2006)

Interpolated (to grid) monthly-average Tave from 1950-99

Warming in all seasons, attributed to increased UHIs or GHGs

Christy et al. (2006)

18 Central Valley sites from 1910-2003 for Tave Tmax,

& Tmin

Increased Tave & Tmin in all seasons,

greater in summer & fall. Summer cooling Tmax & warming

TD values attributed to increased

summer irrigation

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Bonfils & Duffy (2007)

Christy et al. (2006) Tmin

Warming Tmin not due to irri-

gation, which could only overcome GHG-warming for Tmax

Bonfils & Lobell (2007) and Lobell & Bonfils (2008)

Gridded Tmax &

Tmin

Expanded irrigation cooled sum-mer Tmax, while producing negli-

gible effects on Tmin

LaDochy et al. (2007)

331 sites during 1950-2000 for Tave, Tmin, & Tmax

Annual Tave warming at most sites.

Almost all increases due to changes in Tmin (max in sum-mer), as Tmax

showed no change or cooling. Max Tave warming in southern CA, but

NE Interior Basin showed cooling

Abatzoglou et al. (2008)

Coastal sites during 1970-2000 for Tmax

Significant coastal cooling in late summer & early fall

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The Current HypothesisThe Current Hypothesis

INCREASEDINCREASED GHG-INDUCED GHG-INDUCED INLAND TEMPSINLAND TEMPSINCREASED (COAST TO INCREASED (COAST TO INLAND) PRESSURE & TEMP INLAND) PRESSURE & TEMP GRADIENTSGRADIENTS INCREASED INCREASED SEA BREEZESEA BREEZE FREQ, INTENSITY, FREQ, INTENSITY, PENETRATION, &/OR PENETRATION, &/OR DURATION DURATION COASTAL AREAS SHOULD COASTAL AREAS SHOULD SHOW SHOW COOLING SUMMER COOLING SUMMER DAYTIME MAX TEMPSDAYTIME MAX TEMPS (i.e., A (i.e., A REVERSE REACTION)REVERSE REACTION)

NOTE:NOTE: NOT A TOTALLY ORIGINAL NOT A TOTALLY ORIGINAL IDEA IDEA

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CURRENT DATACURRENT DATA• NCDC DAILY MAX & MIN 2-METER TEMPSNCDC DAILY MAX & MIN 2-METER TEMPS

– FROM ABOUT 300 CA NWS COOP SITES (SEE MAP) FROM ABOUT 300 CA NWS COOP SITES (SEE MAP) – FOR 1948-2005FOR 1948-2005– HAVE BEEN USED IN MANY OTHER CA CLIMATE-CHANGE HAVE BEEN USED IN MANY OTHER CA CLIMATE-CHANGE

STUDIESSTUDIES• NCDC MEAN MONTHLY GRIDDED SEA SURFACE NCDC MEAN MONTHLY GRIDDED SEA SURFACE

TEMPSTEMPS (SSTs) (SSTs)– FROM INTERNATIONAL COMPREHENSIVE 0CEAN-ATM DATA FROM INTERNATIONAL COMPREHENSIVE 0CEAN-ATM DATA

SET (ICOADS) SET (ICOADS) – AT 2-DEG HORIZ RESOLUTIONAT 2-DEG HORIZ RESOLUTION– FOR 1880-2004FOR 1880-2004

• NWS 1600-LST DEW-POINT TEMPSNWS 1600-LST DEW-POINT TEMPS – FROM TWO NWS AIRPORT SITES: COASTAL-SFO & INLAND-FROM TWO NWS AIRPORT SITES: COASTAL-SFO & INLAND-

SACSAC– FOR 1970-2005FOR 1970-2005

• ERA40 1.4 DEG REANALYSIS 1000-LST SUMMER T-85 ERA40 1.4 DEG REANALYSIS 1000-LST SUMMER T-85 – SEA-LEVEL PRESSURE CHANGES SEA-LEVEL PRESSURE CHANGES – FOR 1970-2005FOR 1970-2005

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Results 1:Results 1: SoCAB 1970-2005 summer (JJA) T SoCAB 1970-2005 summer (JJA) Tmax max warming/ warming/ cooling trends (cooling trends (00C/decade); C/decade); solid, crossed, & open solid, crossed, & open

circles show stat p-values < 0.01, 0.05, & not circles show stat p-values < 0.01, 0.05, & not

significant, respectivelysignificant, respectively

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Results 2:Results 2: SFBA & CV 1970-2005 JJA SFBA & CV 1970-2005 JJA T Tmaxmax warming/cooling trends ( warming/cooling trends (00C/decade), as in previous C/decade), as in previous

figurefigure

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• LOWER TRENDSLOWER TRENDS FROM 1950- 70 FROM 1950- 70 (EXCEPT FOR T(EXCEPT FOR TMAX)

• Curve b:Curve b: T TMIN HAD HAD FASTEST RISE (AS FASTEST RISE (AS EXPECTED)EXPECTED)

• Curve c:Curve c: T TMAX HAD SLOWEST RISE; IT IS A SMALL-∆ B/T BIG POS VALUE & BIG NEG-VALUE (AS ABOVE)

• CURVE a:CURVE a: TAVE THUS THUS ROSE AT MID RATE ROSE AT MID RATE

• Curve d:Curve d: DTR THUS DTR THUS

DECREASED (AS DECREASED (AS TTMAX FALLS & FALLS & TTMIN RISES)RISES)

Results 3: JJA Temp trends; all CA-sites

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Result 4: JJA TResult 4: JJA Tave, T, Tmin, T, Tmax, & DTR TRENDS FOR, & DTR TRENDS FOR

INLAND-WARMING INLAND-WARMING SITES OF SoCAB & SFBASITES OF SoCAB & SFBA

Curve b:Curve b: T TMIN

INCREASED (EXPECTED)(EXPECTED)

Curve c:Curve c: T TMAX HAD FASTER RISE; (UNEXPECTED), (UNEXPECTED), COULD BE DUE TO COULD BE DUE TO INCREASED UHIsINCREASED UHIs

CURVE a:CURVE a: TAVE THUS THUS

ROSE AT MID RATEROSE AT MID RATE

Curve d:Curve d: DTR THUS DTR THUS INCREASED (AS TINCREASED (AS TMAX ROSE FASTER THAN FASTER THAN TTMIN ROSE ROSE

bb

cc

aa

dd

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Result 5: JJA TResult 5: JJA Tave, T, Tmin, T, Tmax, & DTR TRENDS FOR , & DTR TRENDS FOR

COASTAL-COOLINGCOASTAL-COOLING SITES OF SoCAB & SFBA SITES OF SoCAB & SFBA

Curve b:Curve b: T TMIN ROSE ROSE

(EXPECTED)(EXPECTED)

Curve c:Curve c: T TMAX HAD COOL-ING (UNEXPECTED (UNEXPECTED MAJOR MAJOR RESULTRESULT OF STUDY) OF STUDY)

CURVE a:CURVE a: TAVE THUS SHOWED ALMOST NO CHANGE, AS FOUND IN LIT.), AS RISING T AS RISING Tmin & &

FALLING TFALLING Tmax CHANGES ALMOST CANCELLED OUT

Curve d:Curve d: DTR THUS DE- DTR THUS DE-CREASED, AS TCREASED, AS TMIN ROSE &

TTMAX FELL FELL

aa

bb

cc

dd

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Current coastal-cooling results are Current coastal-cooling results are uniqueunique because study is first to: because study is first to:

• divide obs. in divide obs. in allall the following ways the following ways– summer (JJA)-values onlysummer (JJA)-values only– TTmax & T & Tmin, as well as T, as well as Tave-values-values– coastal vs. inland sitescoastal vs. inland sites

• consider sea-breeze enhancement consider sea-breeze enhancement as as a cau-sal mechanism, instead of: a cau-sal mechanism, instead of: GHGs, GHGs, irrigation, SST, UHI, PDO, &/or aerosols irrigation, SST, UHI, PDO, &/or aerosols (lit (lit review slides, above)review slides, above)

• carry out carry out data analyses data analyses andand meso-met meso-met modeling modeling (next section)(next section)

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SUMMARY OF CURRENT CA SUMMARY OF CURRENT CA OBS OBS

• SUMMER MIN-TEMPSSUMMER MIN-TEMPS IN CALIF HAVE BEEN IN CALIF HAVE BEEN WARMING FASTER THAN WARMING FASTER THAN MAX-TEMPSMAX-TEMPS

• SUMMER DAYTIME MAX-TEMPSSUMMER DAYTIME MAX-TEMPS HAVE BEEN HAVE BEEN COOLING, COOLING, BUT ONLY IN LOW-ELEVATION BUT ONLY IN LOW-ELEVATION COASTALCOASTAL AIR- BASINSAIR- BASINS

• FOLLOWING AREAS ARE FOLLOWING AREAS ARE COOLING IN CENTRAL CA:COOLING IN CENTRAL CA:>MARINE LOWLANDS > MONTEREY>MARINE LOWLANDS > MONTEREY> SANTA CLARA & LIVERMORE VALLIES> SANTA CLARA & LIVERMORE VALLIES> WESTERN SACRAMENTO VALLEY> WESTERN SACRAMENTO VALLEY

• CURRENT OBS ARE, HOWEVER, CONSISTENT WITH (BUT ARE MORE DETAILED & FOCUSED) THAN – CA-COOP LIT-RESULTS (PREVIOUS SLIDES) – IPCC GLOBAL OBS (NEXT SLIDE)

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Note: note IPCC 2001 cooling over SFBA!!

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OUR GROUP’S MESO-MODELING EXPERIENCEOUR GROUP’S MESO-MODELING EXPERIENCE

• SJSU (MM5 & uMM5)SJSU (MM5 & uMM5)– Lozej (1999) MS: SFBA winter wave cyclone– Craig (2002) MS: Atlanta UHI-initiated thunderstorm (NASA)– Lebassi (2005) MS: Monterey sea breeze (LBNL)– Ghidey (2005) MS: SFBA/CV CCOS episode (LBNL)– Boucouvula (2006a,b) Ph.D.: SCOS96 episode (CARB)– Balmori (2006) MS: Tx2000 Houston UHI (TECQ)– Weinroth (2009) PostDoc: NYC-ER UDS urban-barrier effects (DHS))

• SCU (uRAMS)SCU (uRAMS)– Lebassi (2005): Sacramento UHI (SCU) – Lebassi (2009) Ph.D.: SFBA & SoCAB coastal-cooling (SCU)– Comarazamy (2009) Ph.D.: San Juan climate-change & UHI (NASA)

• Altostratus (uMM5 & CAMx)Altostratus (uMM5 & CAMx)– SoCAB (1996, 2008): UHI & ozone (CEC)– Houston (2008): UHI & ozone (TECQ) – Central CA (2008): UHI & ozone (CEC)– Portland (current): UHI & ozone (NSF)– Sacramento (current): UHI & ozone (SMAQMD)

• 2009 =2009 = submitted for presentation at AMS national conf submitted for presentation at AMS national conf

2020

LEBASSI Ph.D. (at SCU): RAMS MESO-MET LEBASSI Ph.D. (at SCU): RAMS MESO-MET SFBA & SoCAB SimulationsSFBA & SoCAB Simulations

RunNo.

GlobalCO2

levels

CoastalSST

values

LU/LC(Agriculture

& Urban)

Notes onConditionssimulated

1 Total Current

2 o Only Past-Global

3 o o Only Past-LU/LC

4 o o o Total Past

where: o = pre-European- & = current-conditions

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Rams Grid ConfigurationRams Grid Configuration

Grid x y z Δx ,Δy Δz Δt

1 80 80 50 60 Km 10m 10s

2 82 82 50 15 km 10m 5s

3 70 70 50 3.75 km 10m 2.5s

•Horizontal GridHorizontal Grid - Arakawa type C staggered - Arakawa type C staggered gridgrid - Three nested grids- Three nested grids

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RAMS SFBA Result 1: Average July-2006, 4 PM RAMS SFBA Result 1: Average July-2006, 4 PM changes changes (present minus past land-use; no GHG changes) in(present minus past land-use; no GHG changes) in

2-m T (2-m T (0C) & 10-m V (m/s) in W-E plane thru Carquinez C) & 10-m V (m/s) in W-E plane thru Carquinez StraitStrait

Land-use changes resulted in increased flow-rate of cool sea-breeze air thru the Strait

V (m/s)

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RAMS Result 2: Vertical profile of T (RAMS Result 2: Vertical profile of T (0C) & V (m/s) C) & V (m/s) changes at 4 PM at point with peak speedchanges at 4 PM at point with peak speed

in Carquinez Strait (in previous slide)in Carquinez Strait (in previous slide)

Results show that increased sea-breeze air flow thru Strait (in previous slide) decreases with altitude & is capped by return-flow aloft (at 350-600 m AGL)

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BENEFICIAL IMPLICATIONS OF BENEFICIAL IMPLICATIONS OF COASTAL COOLINGCOASTAL COOLING

• NAPA WINE NAPA WINE AREAS MAY NOT GO EXTINCTAREAS MAY NOT GO EXTINCT (REALLY GOOD NEWS!; (REALLY GOOD NEWS!; SEE SEE MAP)MAP)

• LOWER HUMAN LOWER HUMAN HEAT-STRESSHEAT-STRESS RATES RATES

• OZONE CONCENTRATIONSOZONE CONCENTRATIONS MIGHT CONTINUE MIGHT CONTINUE TO DECREASE, AS LOWER MAX-TEMPS TO DECREASE, AS LOWER MAX-TEMPS REDUCEREDUCE– ANTHROPOGENIC EMISSIONSANTHROPOGENIC EMISSIONS– BIOGENIC EMISSIONSBIOGENIC EMISSIONS– PHOTOLYSIS RATESPHOTOLYSIS RATES

• ENERGYENERGY FOR COOLING MAY NOT INCREASE FOR COOLING MAY NOT INCREASE AS RAPIDLY AS POPULATION AS RAPIDLY AS POPULATION (4 SLIDES)(4 SLIDES)

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NAPA WINE AREAS MAY NAPA WINE AREAS MAY NOT GO EXTINCTNOT GO EXTINCT DUE TO DUE TO ALLEGED RISING TALLEGED RISING TMAX VALUES, AS PREDICTED IN NAS VALUES, AS PREDICTED IN NAS

STUDYSTUDY

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Implications for Implications for ALL-CA ALL-CA Energy Needs Energy Needs Result 1: Heating Degree-(HDDs) & Result 1: Heating Degree-(HDDs) &

Cooling Degree- (CDDs) DaysCooling Degree- (CDDs) Days

CDDsCDDs• INCREASED AT INCREASED AT LOWER RATE, AS LOWER RATE, AS SUMMER MAX-T SUMMER MAX-T INCREASED AT A INCREASED AT A LOWER RATELOWER RATE

• NEED TO REDO THIS NEED TO REDO THIS FOR COASTAL FOR COASTAL COOLING AREASCOOLING AREAS

HDDsHDDs• DECREASED AT DECREASED AT FASTER RATE (WE DID FASTER RATE (WE DID NOT STUDY WINTER NOT STUDY WINTER MIN-Ts)MIN-Ts)

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Result 2: 1970-2005 SoCAB summer CCD-trends Result 2: 1970-2005 SoCAB summer CCD-trends (degree-days/summer) generally shows:(degree-days/summer) generally shows:

> > decreases in cooling coastal-areas decreases in cooling coastal-areas

> increases in warming inland-areas> increases in warming inland-areas

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Result 3: SAME FOR SoCAB, Result 3: SAME FOR SoCAB, generally shows generally shows > decreases in cooling low-elevation coastal-areas > decreases in cooling low-elevation coastal-areas > increases high-elevation coastal-areas & warming > increases high-elevation coastal-areas & warming

inland-areasinland-areas

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Result 4: Peak-Summer Result 4: Peak-Summer Per-capita Per-capita Electricity-Electricity-TrendsTrends

Down-trend at Down-trend at cooling cooling coastal LA & Pasadena coastal LA & Pasadena ((pinkpink line, 8.5%/decade) line, 8.5%/decade) > Up-trend at warming > Up-trend at warming inland Riversideinland Riverside (green line)(green line)

> Up-trend at > Up-trend at warming warming Sac & Santa ClaraSac & Santa Clara

> Need: detailed > Need: detailed energy-useenergy-use data for data for more sitesmore sites

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POSSIBLE FUTURE EFFORTSPOSSIBLE FUTURE EFFORTS (PART 1 (PART 1 OF 2)OF 2)

• EXPANDED EXPANDED (TO ALL OF CA)(TO ALL OF CA)– ANALYSIS OFANALYSIS OF OBS (IN-SITU & OBS (IN-SITU & GISGIS) ) – URBANIZED MESO-MET (MM5, RAMS, WRF) URBANIZED MESO-MET (MM5, RAMS, WRF)

MODELING MODELING

• SEPARATE INFLUENCES SEPARATE INFLUENCES OF CHANGING:OF CHANGING:– LAND-USE PATTERNS RELAND-USE PATTERNS RE

• AGRICULTURAL IRRIGATIONAGRICULTURAL IRRIGATION• URBANIZATION & UHI-MAGNITUDEURBANIZATION & UHI-MAGNITUDE

– SEA BREEZE:SEA BREEZE:INTENSITY, FREQ, DURATION, &/OR PENETRATION INTENSITY, FREQ, DURATION, &/OR PENETRATION

• DETERMINE POSSIBLE DETERMINE POSSIBLE “SATURATION”“SATURATION” OF OF SEA- BREEZE EFFECTS FROMSEA- BREEZE EFFECTS FROM

• FLOW-VELOCITY & COLD-AIR TRANSPORTFLOW-VELOCITY & COLD-AIR TRANSPORT• AND/OR STRATUS-CLOUD EFFECTS ON LONG- & SHORT-AND/OR STRATUS-CLOUD EFFECTS ON LONG- & SHORT-

WAVE RADIATIONWAVE RADIATION

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POSSIBLE FUTURE EFFORTS POSSIBLE FUTURE EFFORTS (PART 2 (PART 2 OF 2)OF 2)

• DETERMINE CUMULATIVE FREQ DISTRIBU-DETERMINE CUMULATIVE FREQ DISTRIBU-TIONSTIONS OF MAX-TEMP VALUES, AS OF MAX-TEMP VALUES, AS– EVEN IF EVEN IF AVERAGEAVERAGE MAX-VALUES DECREASE, MAX-VALUES DECREASE,– EXTREMEEXTREME MAX-VALUES MAY STILL INCREASE (IN MAX-VALUES MAY STILL INCREASE (IN

INTENSITY AND/OR FREQUENCY)INTENSITY AND/OR FREQUENCY)

• DETERMINE CHANGES IN LARGE-SCALE DETERMINE CHANGES IN LARGE-SCALE ATMOSPHERIC FLOWS:ATMOSPHERIC FLOWS:– HOW DOES GLOBAL CLIMATE-CHANGE EFFECT HOW DOES GLOBAL CLIMATE-CHANGE EFFECT

POSITION & STRENGTH OF: POSITION & STRENGTH OF: PACIFIC HIGH & THERMAL PACIFIC HIGH & THERMAL LOW?LOW?

– THIS IS THIS IS ULTIMATE CAUSEULTIMATE CAUSE OF CLIMATE-CHANGE OF CLIMATE-CHANGE

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ConclusionConclusion• Coastal-coolingCoastal-cooling of CA summer day-time max- of CA summer day-time max-

temps needs consideration in future energy temps needs consideration in future energy planning, along with changes in: planning, along with changes in: population & population & efficiencyefficiency

• The SJSU/SCU/Altostratus groupThe SJSU/SCU/Altostratus group– has deep experience in has deep experience in analysis & simulationanalysis & simulation of meso- of meso-

scale met processes in Californiascale met processes in California– can provide support to ongoing internal & external can provide support to ongoing internal & external

CEC efforts in CEC efforts in climate downscaling & energy trend climate downscaling & energy trend analysesanalyses

– can can downscale GCM-outputdownscale GCM-output down to grids of 1-5 km, down to grids of 1-5 km, so as to resolve CA coastal-topographic-urban so as to resolve CA coastal-topographic-urban influences influences

– has existing CA efforts that could be has existing CA efforts that could be leveragedleveraged by by new CEC support new CEC support

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Thanks for listening!Thanks for listening!

Additional questions and Additional questions and discussion?discussion?