Global-warming reverse-impact: observed summer-daytime coastal-cooling in coastal California air-basins R. Bornstein, San Jose State University [email protected].

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

[email protected]@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 UNAMPresented at UNAM23 Feb 200723 Feb 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 – for land and seafor land and sea– zero-line is for a sub zero-line is for a sub

periodperiod– 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-T-Taver(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 at slower Warming at slower

rate than at inland rate than at inland sitessites

Reverse-Impact Reverse-Impact HypothesisHypothesis

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

INLAND) ∂(p,T)/ ∂nINLAND) ∂(p,T)/ ∂n

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

CURRENT ANALYSESCURRENT ANALYSES• 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-box andSST: SFBA black-box and– 2-m land-values:2-m land-values: red-box red-box

All-Calif Asymmetric-Warming: 1970-All-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 b/t 2 large nos.)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 breezefor boxes of previous for boxes of previous slideslide

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)

-

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

(ignore: needs recalculation)(ignore: needs recalculation)• 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)

Statistical Significance: 1970-2005Statistical Significance: 1970-2005(high r (high r low N low Ne low significance) low significance)

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 • Expected: Expected: CACA T TMIN WARMED FASTER THAN WARMED FASTER THAN

TTMAX ASYMMETRIC WARMINGASYMMETRIC WARMING

• New: SUMMER DAYTIME CA TNew: SUMMER DAYTIME CA TMAX COOLEDCOOLED IN IN FOL-LOWING LOW-ELEVATION FOL-LOWING LOW-ELEVATION COASTALCOASTAL AIR- AIR- BASINSBASINS– 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 NOT SHRINKMAY NOT SHRINKe.g.: e.g.: NAPA WINE NAPA WINE AREAS AREAS MAY NOT GO EXTINCT, AS MAY NOT GO EXTINCT, AS PRE-DICTEDPRE-DICTED

• ENERGYENERGY FOR COOLING FOR COOLING

MAY NOT INCREASE AS MAY NOT INCREASE AS RAPIDLY AS POPULATIONRAPIDLY AS POPULATION

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

GOOD IMPLICATIONS FOR CALIF GOOD IMPLICATIONS FOR CALIF

OZONEOZONE • PAST DECREASES MAY BE IN-PART DUE TO PAST DECREASES MAY BE IN-PART DUE TO

JJA MAX-TEMP COOLING-TRENDS JJA MAX-TEMP COOLING-TRENDS & NOT & NOT ONLYONLY TO EMISSION REDUCTIONS, AS TO EMISSION REDUCTIONS, AS PREVIOUSLY THOUGHTPREVIOUSLY THOUGHT

• WHEN TWHEN Tmax DECREASES, THE FOLLOWING 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 ANALYSIS OF OBS & MESO MET REQUIRED ANALYSIS OF OBS & MESO MET MODELING TO EVALUATE FOLLOWING MODELING TO EVALUATE FOLLOWING

INFLUENCES DISCUSSED IN LITERATURE INFLUENCES DISCUSSED IN LITERATURE • WARMING SSTs WARMING SSTs weaker sea breezes weaker 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 weaker sea-breezes weaker sea-breezes– COASTAL URBANIZATION: STRONGER UHIs COASTAL URBANIZATION: STRONGER UHIs

stronger sea-breezes stronger sea-breezes • OTHER SEA-BREEZE INFLUENCES: OTHER SEA-BREEZE INFLUENCES:

INCREASEDINCREASEDWIND VELOCITY, STRATUS CLOUDS, & SOIL MOISTURE WIND VELOCITY, STRATUS CLOUDS, & SOIL MOISTURE coastal cooling coastal cooling stronger sea breezes stronger sea breezes

WHERE TO LOOK FOR WHERE TO LOOK FOR REVERSE-IMPACTSREVERSE-IMPACTS

• WHERE TO LOOK FOR COASTAL-COOLINGWHERE TO LOOK FOR COASTAL-COOLING– GC winds in same-direction as sea-breezeGC winds in same-direction as sea-breeze– Low-elevation air-basinsLow-elevation air-basins– Cool coastal ocean-currentsCool coastal ocean-currents– Upwelling areasUpwelling areas

i.e.:i.e.: mid-lat (what lat range?) W-coast mid-lat (what lat range?) W-coast areasareas

• What other-types of What other-types of reverse-impacts reverse-impacts might might existexist– e.g.,e.g., in high-elevation areas? in high-elevation areas?– Must ask the “right-questions” Must ask the “right-questions”

THANKS!THANKS!

Any further questions?Any further questions?