1. EFFECTS OF CLIMATE CHANGE ON FOREST FIRES OVER NORTH AMERICA AND IMPACT ON U.S. OZONE AIR QUALITY
Rynda Hudman 1,2, Dominick Spracklen 1,3, Jennifer Logan3 Loretta J. Mickley3, Maria Val Martin3, Shiliang Wu3,4, Rose Yevich3, Alan Cantin5, Mike Flannigan5, Tony Westerling6
Affiliations: 1 School of Engineering, Harvard Now at UC Berkeley Now at University of Leeds Now at Michigan Tech Canadian Forest Service UC Merced

2. OBSERVED INCREASE IN WILDFIRE ACTIVITY OVER NORTH AMERICA
Area burned in Canada has increased since the 1960s, correlated with temp. increase.
5 year means
[Gillett et al., 2004]
Increased fire frequency over western U.S. in recent decades – related to warmer temp., earlier snow melt.
[Westerling et al., 2007]

3. PREDICTING FUTURE FIRE IMPACTS ON U.S. OZONE
OBSERVED AREA BURNED
WEATHER & FUEL MOISTURE/ FIRE SEVERITY
AREA BURNED
PREDICTION
Yearly Area Burned = C1X1 + C2X2 + … + C0
GISS GCM
Output
(2050, A1B)
FUTURE AREA BURNED
GEOS-CHEM CTM
Emissions
Future Fire Impacts on U.S. ozone air quality

4. PREDICTED BIOMASS CONSUMPTION BY FIRES IN THE WESTERN U.S., 1996-2055
Results shown as the number of standard deviations away from the mean for
50% increase in biomass consumption by 2050  40% increase in mean summertime aerosol concentration
[Further details see Spracklen et al., JGR, in review]

5. PROJECTED WESTERN U.S. WILDFIRE NOx EMISSIONS Ozone production generally limited by supply of NOx
2046 – 2055 PROJECTED WILDFIRE NOx EMISSIONS ARE 50% LARGER THAN
* We assume forest emission factor of 1.6 g NO/kg DM

6. PREDICTED AFTERNOON (1-5pm) JULY MEAN OZONE ENHANCEMENT 1-3 PPBV
4 Years Future (2050) vs. 4 Years Present (2000)
Ozone change due to future wildfire*
* Note: climate effects have been subtracted out
Consistent with these results, recent observational estimates of regional enhancements of 2 ppbv for each 1 million acres burned [Jaffe et al., 2008]

7. REGRESSIONS CAPTURE VARIABILITY IN REGIONS WITH LARGEST AREA BURNED
Historical Area Burned
Regressions ‘capture’ 15 – 62% of variability over Canada and Alaska.
R2 of Area Burned regressions
[Nancy French, MTU]
[Stocks et al., 1999]

8. REGRESSION AGAINST AREA BURNED: Taiga Plains
ALASKA/CANADA SUMMARY
Most Common Predictors:
Monthly/Seas. 500 mb GPH Anomaly
Max/Mon./Seasonal Severity Rating
Large-scale Ocean/Atmosphere circulation related to fire activity [ e.g., Skinner et al., 1999, 2002; Duffy et al., 2005] ; Severity Rating &Temp common predictor in previous regression [Balschi et al., 2008]

9. DOES RAIN OFFSET TEMPERATURE INCREASE?
Simulated May – August vs
June 500mb anomaly over Fairbanks, Alaska (1940 – 2006)
GISS Mean : dm
: dm
GISS Mean : dm :
[Fairbanks GPH Courtesy of Sharon Alder, BLM]

10. AREA BURNED PROJECTIONS
34% increase over Alaska, 8% change over Canada w/ large regional variability
Difference from other studies likely due to future scenario or GCM  need envelope study with multiple GCMs & scenarios.

11. PRESENT DAY FIRE IMPACTS ON OZONE
Ozone enhancement from NA biomass burning 0-2 km
Simulated July 2004 mean
Max enhancement during July

12. CONCLUSIONS
Regressions capture much of the variability in annual area burned over the western U.S. (24-57%), Alaska (53-57%), and Canada (15-62%). Key predictors : 500 mb GPH anomaly & severity rating.
2050 climate change (A1B) increases annual mean area burned: Alaska (+34%) and the western U.S. (+54%) relative to the present-day, but unlike previous studies little change over Canada as a whole (8%), due to increases in GCM precipitation (scenario/GCM dependent).
Future fires increase NOx emissions over the western United States by 50%, resulting in a large scale 1-3 ppbv enhancement in summertime afternoon ozone, though inter annual effects larger.
Long-range transport impacts largest over central U.S. with large scale episodic ozone enhancements > 5 ppbv over large areas of the Northern U.S., comparable to W. U.S. ozone enhancements.

13. EXTRAS

14. CANADIAN FUTURE AREA BURNED PROJECTIONS
Increased precipitation counterbalanced by increased 500mb GPH anom.
Taiga Plains
Increases of ~15% in summertime precipitation  -40% AB
Boreal Shield West
Increased GPH anomaly counterbalances increases in precipitation  + 21% AB

15. Soja et. al.

16. We capture between 50-60% for the two Alaska ecoregions
Regression (in red) chosen from 22 surface met & FWI variables (1959 – 2006) and 500 mb data from Fairbanks, Alaska
Note: DSR = Daily Severity Rating = f(T, RH, Rain)
Ecozones

17. Both DSR and 500 mb anom govern variability in this region
Ecozones

18. Area Burned and GISS Regression
Met Corrected with:
(500 mb anom) (MaxDSR)
(500 mb anom) (MeanTemp) –

19. Station location Fire distribution Ecoregions61 11 14 12 4 62 9 51 53 52
Ecoregions
4- Taiga Plains (120m) Boreal Cordillera (415m) Boreal Shield East (170m) Boreal Plains (388m) Montane Cordillera (747m) Taiga Shield West (192m) 11- Taiga Cordillera(415m) Boreal Shield West (348m) 52 – Taiga Shield East (27m) – Hudson Plains(152m)

21. ….AND FUEL CONSUMPTION
Fuel bed map (1x1 km resolution) from Nadeau et al, [2005]
[Maria Val Martin]

22. NEW EMISSIONS WILL ACCOUNT FOR SEASONAL CHANGE IN FUEL MOSITURE…
Fuel Consumption Changes in Black Spruce-Lichen Woodland Forest
Drier Conditions
Late Season
Wetter Conditions
Early Season
[Maria Val Martin]