Global-warming Global-warming reverse-impactreverse-impact::observed summer-daytime coastal-observed summer-daytime coastal-

coolingcoolingin coastal California air-basinsin coastal California air-basins

R. BornsteinR. Bornstein, San Jose State University, San Jose State University

pblmodel@hotmail.compblmodel@hotmail.com

B. Lebassi, J. E. González, D. Fabris, B. Lebassi, J. E. González, D. Fabris, E. Maurer, Santa Clara UniversityE. Maurer, Santa Clara University

N. Miller, Berkeley National LaboratoryN. Miller, Berkeley National Laboratory

Presented at ASUPresented at ASU26 Jan 200726 Jan 2007

OUTLINEOUTLINE • Global warmingGlobal warming• Reverse impactsReverse impacts• Coastal cooling observationsCoastal cooling observations

– MethodologyMethodology– ResultsResults

•South Coast Air BasinSouth Coast Air Basin•SFBA and Central ValleySFBA and Central Valley

• ConclusionsConclusions– Summary Summary – ImplicationsImplications

• FUNDING: NSF and Santa Clara UniversityFUNDING: NSF and Santa Clara University

Global WarmingGlobal Warming• Models:Models: past & future past & future

asymmetric-warmingasymmetric-warming

(i.e., (i.e., ΔΔTTminmin > > ΔΔTTmaxmax) ) onon– global scale (1.0-2.5 global scale (1.0-2.5

deg resolution) deg resolution) – regional scale (10 km regional scale (10 km

resolution)resolution)

• Global scale obsGlobal scale obs – match model resultsmatch model results– show accelerated-show accelerated-

warming since ‘70s warming since ‘70s

California Warming: California Warming: JJA 1900-2000 JJA 1900-2000 ΔΔ--TTaver(K)(K)

• USC Stat-downscaledUSC Stat-downscaled global-model results global-model results – 2-m AGL2-m AGL– 10-km horiz-grid 10-km horiz-grid – warming-rates warming-rates

decrease towards decrease towards coast coast

• CoastalCoastal SSTsSSTs – ICOADS dataICOADS data– 2-deg horiz resolution2-deg horiz resolution– Warming, butWarming, but– At slower rate than at At slower rate than at

inland sitesinland sites

Reverse-Impact Reverse-Impact HypothesisHypothesis

INLAND WARMING INLAND WARMING INCREASED (COAST TO INCREASED (COAST TO

INLAND) INLAND) ∂(p,∂(p,T)/ T)/ ∂∂nn

INCREASED SEA INCREASED SEA BREEZE BREEZE FREQ, FREQ, INTENSITY, INTENSITY, PENETRATION, & PENETRATION, & DURATION DURATION

COOLING SUMMER COOLING SUMMER COASTAL TCOASTAL Tmax

CALIF TEMP-DATACALIF TEMP-DATA

• FROM NCDC FROM NCDC

• 2-m VALUES 2-m VALUES

• DAILY TDAILY TMAX & T & TMIN

• 300 NWS CO-OP 300 NWS CO-OP SITESSITES

• 1948-20051948-2005

ANALYSESANALYSES• 1970-2005 data used1970-2005 data used• Annual & summer Annual & summer

warming/ cooling trends warming/ cooling trends (K/decade) for SST, T(K/decade) for SST, Tmaxmax, , TTminmin

• Spatial dist of summer Spatial dist of summer

TTmax-trends plotted -trends plotted (in 2 black boxes) (in 2 black boxes) – South Coast Air Basin South Coast Air Basin – SFBA and Central Valley SFBA and Central Valley

• Summer land-sea TSummer land-sea Taver--grad (surrogate for p-grad (surrogate for p-grad) trend calculated by grad) trend calculated by use of use of – SST: SFBA black-boxSST: SFBA black-box– 2-m land-values:2-m land-values: red-box red-box

Calif Asymmetric-Warming: 1970-Calif Asymmetric-Warming: 1970-

20052005 • Middle curve (TMiddle curve (Tminmin)= )=

0.27 K/decade0.27 K/decade• Lower curve (TLower curve (Tmax)max)==

0.061 K/decade0.061 K/decade(small-(small-ΔΔ b/t 2 large nos.) b/t 2 large nos.)

• Top curve (SST)=Top curve (SST)=0.24 K/decade0.24 K/decade

**********************• Thus, from TThus, from Taveraver & SST: & SST:

Right curve (T-grad)=Right curve (T-grad)= 0.16 K/100-km/decade 0.16 K/100-km/decade stronger sea breezestronger sea breeze

Changes in Diurnal temperature-range (DTR) values at Changes in Diurnal temperature-range (DTR) values at all Calif all Calif • daytime-warming (mainly inland) sites:daytime-warming (mainly inland) sites: 0.05 0.05 K/decade K/decade

(as T(as Tmax increased a bit faster than did Tincreased a bit faster than did Tmin))• daytime-cooling (mainly coastal) sites:daytime-cooling (mainly coastal) sites: -0.61 -0.61 K/decadeK/decade

(as T(as Tmax decreased and Tcreased and Tmin increased) increased)

Significant South Coast Significant South Coast Air Basin TopographyAir Basin Topography

SCAB 1970-2005 summerSCAB 1970-2005 summer T Tmax max warming/cooling trends (K/decade) warming/cooling trends (K/decade)

Significant SFBA and CenValleySignificant SFBA and CenValleyTopographyTopography

SFBA & CenV 1970-2005 summerSFBA & CenV 1970-2005 summerTTmaxmax warming/cooling trends (K/decade) warming/cooling trends (K/decade)

-

Statistical Significance: 1970-2005Statistical Significance: 1970-2005

Parameter (all Calif)Rate

(K/decade) r

Ne

(years)

Significance(%)

DTR (cooling areas) -0.61 0.70 6 95

DTR (warming areas) 0.05 0.07 31 32

Tmin 0.27 0.52 11 93

Tmax 0.06 0.09 30 68

SST 0.24 0.45 14 92

100-km dT/dx 0.16 0.10 30 40

Region-AreaRate

(K/decade) r

Ne

(years)Significance

(%)

Coastal-SFBA -0.16 0.23 22 72

Inland-SFBA 0.47 0.58 10 95

Coastal-SoCAB -0.33 0.37 17 87

Inland-SoCAB 0.21 0.25 22 74

Coastal-Both -0.22 0.32 19 83

Inland-Both 0.40 0.53 11 93

SUMMARY SUMMARY • MIN-TEMPSMIN-TEMPS IN CALIF WARMED FASTER IN CALIF WARMED FASTER

THAN THAN MAX-TEMPS MAX-TEMPS ASYMMETRIC ASYMMETRIC WARMINGWARMING

• SUMMER DAYTIME MAX-TEMPSSUMMER DAYTIME MAX-TEMPS COOLEDCOOLED IN IN LOW-ELEVATION LOW-ELEVATION COASTALCOASTAL AIR- BASINS AIR- BASINS

• FOLLOWING AREAS FOLLOWING AREAS COOLED IN CENTRAL COOLED IN CENTRAL CALIFORNIA:CALIFORNIA:– MARINE LOWLANDSMARINE LOWLANDS– MONTEREYMONTEREY– SANTA CLARA VALLEYSANTA CLARA VALLEY– LIVERMORE VALLEYLIVERMORE VALLEY– WESTERN HALF OF SACRAMENTO VALLEYWESTERN HALF OF SACRAMENTO VALLEY

GOOD IMPLICATIONSGOOD IMPLICATIONS

• AGRICULTURAL AREAS AGRICULTURAL AREAS MAY MAY NOT SHRINKNOT SHRINKe.g.: e.g.: NAPA WINE NAPA WINE AREAS MAY AREAS MAY NOT GO EXTINCTNOT GO EXTINCT

• ENERGY-ENERGY-NEED FOR COOLING NEED FOR COOLING MAY NOT INCREASE AS MAY NOT INCREASE AS RAPIDLY AS POPULATIONRAPIDLY AS POPULATION

• LOWER HUMAN LOWER HUMAN HEAT-HEAT-STRESSSTRESS & MORTALITY RATES & MORTALITY RATES

• URBAN-OZONEURBAN-OZONE LEVELS WILL LEVELS WILL CONTINUE TO FALLCONTINUE TO FALL

IMPLICATIONS FOR CALIF IMPLICATIONS FOR CALIF OZONE OZONE

• PAST DECREASES MAY BE IN-PART DUE TO PAST DECREASES MAY BE IN-PART DUE TO JJA MAX-TEMP COOLING-TRENDS & NOT JJA MAX-TEMP COOLING-TRENDS & NOT ONLY TO EMISSION REDUCTIONSONLY TO EMISSION REDUCTIONS

• WHEN MAX-T DECREASES, THE FOLLOWING WHEN MAX-T DECREASES, THE FOLLOWING ALSO DECREASEALSO DECREASE::– BIOGENIC PRECURSOR EMISSIONSBIOGENIC PRECURSOR EMISSIONS

– PHOTOCHEM REACTION RATES PHOTOCHEM REACTION RATES

– ENERGY-USE FOR COOLING AND THUS ENERGY-USE FOR COOLING AND THUS ANTHROPOGENIC PRECURSOR EMISSIONSANTHROPOGENIC PRECURSOR EMISSIONS

REQUIRED FUTURE-EFFORTS:REQUIRED FUTURE-EFFORTS:ANALYSIS OF OBS & MESO MET MODELINGANALYSIS OF OBS & MESO MET MODELING

TO SEPARATE-OUT INFLUENCES TO SEPARATE-OUT INFLUENCES (DISCUSSED IN LITERATURE) OF (DISCUSSED IN LITERATURE) OF

• WARMING SSTs WARMING SSTs weaker sea breezesweaker sea breezes

• INCREASED COASTAL UPWELLING INCREASED COASTAL UPWELLING stronger sea breezes stronger sea breezes

• LAND-USE CHANGESLAND-USE CHANGES– AGRICULTURAL: INCREASED INLAND IRRIGATION AGRICULTURAL: INCREASED INLAND IRRIGATION

inland cooling inland cooling decreased sea-breezes decreased sea-breezes– URBANIZATION: STRONGER UHIs URBANIZATION: STRONGER UHIs

increased sea-breezes increased sea-breezes • OTHER SEA-BREEZE INFLUENCESOTHER SEA-BREEZE INFLUENCES

INCREASEDINCREASED WIND VELOCITY, STRATUS CLOUD WIND VELOCITY, STRATUS CLOUD COVER, & SOIL MOISTURE COVER, & SOIL MOISTURE

coastal cooling coastal cooling

WHERE TO LOOK FOR WHERE TO LOOK FOR COASTAL-COOLINGCOASTAL-COOLING

• GC winds in same-direction as sea-GC winds in same-direction as sea-breezebreeze

• Low-elevation air-basinsLow-elevation air-basins• Cool coastal ocean-currentsCool coastal ocean-currents• Upwelling areasUpwelling areasi.e.:i.e.: mid-lat (what lat range?) west-coast mid-lat (what lat range?) west-coast

areasareasWhat other-types of What other-types of reverse-impacts reverse-impacts

might exist, might exist, e.g.,e.g., in mt areas? in mt areas?

THANKS!THANKS!

Any further questions?Any further questions?