Global-warming reverse-impact: observed summer-daytime coastal-cooling in coastal California air-basins R. Bornstein, San Jose State University B. Lebassi, J. E. González, D. Fabris, E. Maurer, Santa Clara University N. Miller, Berkeley National Laboratory Presented at UNAM 23 Feb 2007

OUTLINE Global warming Global warming Reverse impacts Reverse impacts Coastal cooling observations Coastal cooling observations –Methodology –Results South Coast Air Basin South Coast Air Basin SFBA and Central Valley SFBA and Central Valley Conclusions Conclusions –Summary –Implications FUNDING: NSF and Santa Clara University FUNDING: NSF and Santa Clara University

Global Warming Models: past & future asymmetric-warming Models: past & future asymmetric-warming (i.e., ΔT min > ΔT max ) on (i.e., ΔT min > ΔT max ) on –global scale ( deg resolution) –regional scale (10 km resolution) Global scale obs Global scale obs –for land and sea –zero-line is for a sub period –match model results –show accelerated- warming since ‘70s

California Warming: JJA Δ-T(K) California Warming: JJA Δ-T aver (K) USC Stat-downscaled global-model results USC Stat-downscaled global-model results –2-m AGL –10-km horiz-grid –warming-rates decrease towards coast Coastal SSTs Coastal SSTs –ICOADS data –2-deg horiz resolution –Warming at slower rate than at inland sites

Reverse-Impact Hypothesis INLAND WARMING  INCREASED (COAST TO INLAND) ∂(p,T)/ ∂n  INCREASED SEA BREEZE FREQ, INTENSITY, PENETRATION, & DURATION  COOLING SUMMER COASTAL T COOLING SUMMER COASTAL T max

CALIF TEMP-DATA FROM NCDC FROM NCDC 2-m VALUES 2-m VALUES DAILY T & T DAILY T MAX & T MIN 300 NWS CO-OP SITES 300 NWS CO-OP SITES

CURRENT ANALYSES CURRENT ANALYSES data used data used Annual & summer warming/ cooling trends (K/decade) for SST, T max, T min Annual & summer warming/ cooling trends (K/decade) for SST, T max, T min Spatial dist of summer Spatial dist of summer T-trends plotted T max -trends plotted (in 2 black boxes) –South Coast Air Basin –SFBA and Central Valley Summer land-sea T-grad (surrogate for p-grad) trend calculated by use of Summer land-sea T aver -grad (surrogate for p-grad) trend calculated by use of –SST: SFBA black-box and –2-m land-values: red-box

All-Calif Asymmetric-Warming: Middle curve (T min )= Middle curve (T min )= 0.27 K/decade Lower curve (T max) = Lower curve (T max) = K/decade (small-Δ b/t 2 large nos.) Top curve (SST)= Top curve (SST)= 0.24 K/decade *********** *********** Thus, from T aver & SST: Thus, from T aver & SST: Right curve (T-grad)= 0.16 K/100-km/decade  stronger sea breeze for boxes of previous slide

Significant South Coast Air Basin Topography

SCAB summer T max warming/cooling trends (K/decade)

Significant SFBA and CenValley Topography

SFBA & CenV summer T max warming/cooling trends (K/decade) -

Diurnal temperature-range (DTR) values at Diurnal temperature-range (DTR) values at daytime-warming (mainly inland) sites: 0.05 K/decade daytime-warming (mainly inland) sites: 0.05 K/decade (ignore: needs recalculation) daytime-cooling (mainly coastal) sites: K/decade daytime-cooling (mainly coastal) sites: K/decade (as Tcreased and T increased) (as T max decreased and T min increased)

Statistical Significance: (high r  low N  low significance) Statistical Significance: (high r  low N e  low significance) Parameter (all Calif) Rate (K/decade)r N e (years) Significance (%) DTR (cooling areas) DTR (warming areas) T min T max SST km dT/dx Region-Area Rate (K/decade)r N e (years) Significance (%) Coastal-SFBA Inland-SFBA Coastal-SoCAB Inland-SoCAB Coastal-Both Inland-Both

SUMMARY Expected: CA T WARMED FASTER THAN T  ASYMMETRIC WARMING Expected: CA T MIN WARMED FASTER THAN T MAX  ASYMMETRIC WARMING New: SUMMER DAYTIME CA T COOLED IN FOL- LOWING LOW-ELEVATION COASTAL AIR- BASINS New: SUMMER DAYTIME CA T MAX COOLED IN FOL- LOWING LOW-ELEVATION COASTAL AIR- BASINS –MARINE LOWLANDS –MONTEREY –SANTA CLARA VALLEY –LIVERMORE VALLEY –WESTERN HALF OF SACRAMENTO VALLEY

GOOD IMPLICATIONS AGRICULTURAL AREAS MAY NOT SHRINK AGRICULTURAL AREAS MAY NOT SHRINK e.g.: NAPA WINE AREAS MAY NOT GO EXTINCT, AS PRE- DICTED  ENERGY FOR COOLING MAY NOT INCREASE AS RAPIDLY AS POPULATION ENERGY FOR COOLING MAY NOT INCREASE AS RAPIDLY AS POPULATION LOWER HUMAN HEAT-STRESS & MORTALITY RATES LOWER HUMAN HEAT-STRESS & MORTALITY RATES

GOOD IMPLICATIONS FOR CALIF OZONE PAST DECREASES MAY BE IN-PART DUE TO JJA MAX-TEMP COOLING-TRENDS & NOT ONLY TO EMISSION REDUCTIONS, AS PREVIOUSLY THOUGHT PAST DECREASES MAY BE IN-PART DUE TO JJA MAX-TEMP COOLING-TRENDS & NOT ONLY TO EMISSION REDUCTIONS, AS PREVIOUSLY THOUGHT WHEN T DECREASES, THE FOLLOWING ALSO DECREASE: WHEN T max DECREASES, THE FOLLOWING ALSO DECREASE: – BIOGENIC PRECURSOR-EMISSIONS – PHOTOCHEM REACTION-RATES – ENERGY-USE FOR COOLING, AND THUS ANTHROPOGENIC PRECURSOR-EMISSIONS

REQUIRED ANALYSIS OF OBS & MESO MET MODELING TO EVALUATE FOLLOWING INFLUENCES DISCUSSED IN LITERATURE WARMING SSTs  weaker sea breezes WARMING SSTs  weaker sea breezes INCREASED COASTAL UPWELLING  INCREASED COASTAL UPWELLING  stronger sea breezes LAND-USE CHANGES LAND-USE CHANGES –AGRICULTURAL: INCREASED INLAND IRRIGATION  inland cooling  weaker sea-breezes –COASTAL URBANIZATION: STRONGER UHIs  stronger sea-breezes stronger sea-breezes OTHER SEA-BREEZE INFLUENCES: INCREASED OTHER SEA-BREEZE INFLUENCES: INCREASED WIND VELOCITY, STRATUS CLOUDS, & SOIL MOISTURE  coastal cooling  stronger sea breezes

WHERE TO LOOK FOR REVERSE-IMPACTS WHERE TO LOOK FOR COASTAL-COOLING WHERE TO LOOK FOR COASTAL-COOLING –GC winds in same-direction as sea-breeze –Low-elevation air-basins –Cool coastal ocean-currents –Upwelling areas i.e.: mid-lat (what lat range?) W-coast areas What other-types of reverse-impacts might exist What other-types of reverse-impacts might exist –e.g., in high-elevation areas? –Must ask the “right-questions”

THANKS! Any further questions?