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Wildfire in the western United States in the mid-21st century and consequences for air quality:

Wildfire in the western United States in the mid-21st century and consequences for air quality: Results from an ensemble of climate model projections. . NASA Air Quality Applied Sciences Team serves as a bridge between NASA science and environmental management . Loretta J. Mickley

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Wildfire in the western United States in the mid-21st century and consequences for air quality:

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  1. Wildfire in the western United States in the mid-21st century and consequences for air quality: Results from an ensemble of climate model projections. NASA Air Quality Applied Sciences Team serves as a bridge between NASA science and environmental management. Loretta J. Mickley XuYue Jennifer A. Logan Jed Kaplan, Univ of Geneva

  2. Millions of people in US live in areas with unhealthy levels of ozone or particulate matter (PM2.5). Number of people living in areas that exceed the national ambient air quality standards (NAAQS) in 2010. Ozone daily maximum 8-hour average PM2.5 24-hour average or annual average Bars on barplot will change with changing emissions. Climate change could also change the size of these bars, by changing the day-to-day weather.

  3. VOCs -- volatile organic compounds NH3 -- ammonia . . . . . . SO2 -- sulfur dioxide NOx -- nitrogen oxides Life cycle of particulate matter (PM, aerosols) ultra-fine (<0.01 mm) fine (0.01-1 mm) cloud (1-100 mm) precursor gases nucleation cycling coagulation condensation Soup of chemical reactions coarse (1-10 mm) Organic carbon scavenging Black carbon SO2 SO2 VOCs NOx NOx VOCs NOx NH3 VOCs NOx VOCs NOx combustion volcanoes agriculture biosphere soil dust sea salt wildfires combustion

  4. Effects of wildfires on air quality in cities in Western US can be very dramatic. • Hayman fire, June 8-22, 2002 • 56,000 ha burned • 30 miles from Denver and Colorado Springs Unhealthy air quality in Denver June 9, 2002 June 8, 2002 PM10 = 372 μg/m3 PM2.5 = 200 μg/m3 Standard = 35 µg/m3 PM10 = 40 μg/m3 PM2.5 = 10 μg/m3 Colorado Dept. of Public Health and Environment Vedal et al., 2006

  5. Fire activity had a big impact on California air quality in 2013. Rim Fire Timeseries of 3-hour average PM2.5 concentrations in Foothills Area Hazardous levels > 250 mg m-3 PM2.5 (mg m-3) Very unhealthy Aug 28 August 31 August 20 Will fire change in the future climate? Unhealthy air Very unhealthy air Aug 30

  6. Observations suggest that fires are increasing in North America. Area burned in Canada has increased since the 1960s, correlated with temperature increase. obs temperature area burned Gillett et al., 2004 5 yr means 1960 2000 Increased fire frequency over the western U.S. since 1970, related to warmer temperatures and earlier snow melt. 1970 2000 Westerling et al., 2007

  7. IPCC AR4 models show increasing temperatures across North America by 2100 in A1B scenario. Change in surface temperatures in 2100, relative to present-day. Results for precipitation changes are not so clear. IPCC, 2007

  8. Future regional predictions for precipitation show large variation across North America. Percent change in 2100 precipitation relative to present-day JJA Annual DJF Number of models showing increasing precipitation most models few models IPCC 2007

  9. How do we predict fires in a future climate?We don’t have a good mechanistic approach for modeling wildfires. Start with the past. 2 approaches Use ensemble of climate models to gain confidence in prediction. + JJA Temperature increase by 2100 Relationship between observed meteorology + area burned Future area burned Future meteorology

  10. Approach 1. Regression method. Regress meteorological variables and fire indexes onto annual mean area burned in each of six ecoregions with a stepwise approach. ERM RMF PNW NMS Identify the meteorological variables and fire indexes that best predict area burned. Include lagged met variables. CCS DSW Ecoregions are aggregates of those in Bailey et al. (1994) Best predictors: Temp, RH, precip, Build-up Index, Drought code, Duff moisture code. E.g., Area burned in Nevada/ semi-desert = f ( + T summer max that year + RH and rainfall previous years)

  11. Predicted fires match observed area burned reasonably well. Least best fit is in Southern California. Obs Fit RMF ERM PNW NMS CCS DSW Area burned in many ecoregions depends on previous year’s relative humidity, rainfall, or temp. Yue et al., 2013

  12. Approach 2. Parameterization method. Parameterize daily area burned in each grid square as a function of that day’s temperature, relative humidity, and rainfall. Area burned = f1(Temp) x f2(RH) x f3(rainfall) Fire potential coefficients are (α) chosen to match long-term area burned for each ecoregion. Scheme can predict seasonality of fires on the 1°x1° grid.

  13. Parameterization works for forested regions, but not for regions where meteorology from previous seasons matter. Obs Fit Yue et al., 2013

  14. Start with the past. + Relationship between observed meteorology + area burned Future area burned Future meteorology

  15. Use of an ensemble of 15 climate models improves confidence in the results. • Changes in 2050s climate in the West. • Temperature increases 2-2.5 K. • Changes in precip and relative humidity are small and not always robust. • Next step: apply meteorology from climate models to the two fire prediction schemes. Yue et al., 2013

  16. Wildfire area burned increases across the western United States by the 2050s timeframe. Results from regressions approach. Shown are median results. Yue et al., 2013 + Relationship between observed meteorology + area burned Future area burned Future meteorology

  17. 1986-2000 Models predict increases in area burned of 20-100% across the West, depending on ecoregion. 2051-2065 +40% 1986 2065 Obs +20% Median of models spread of models 100% Area burned (ha) +60% Results are from regressions. +70% The models match the mean area burned fairly well in present-day. +60% Yue et al., 2013

  18. Median model results show an increase in area burned in all regions, but some scatter. Median changes: 40-70% increase in forested regions 60% increase in grasslands Doubling in Southwest Ratio of future to present-day area burned Forest Forest median Ratio of area burned RMF ERM PNW NMS Pacific Northwest Desert Southwest Eastern Rockies Rocky Mountains CCS Nevada Mountains DSW California Coastal Shrub Yue et al., 2013

  19. Parameterization method shows similar increases in area burned, and also provides seasonality. Units = 104 hectares future present-day X2 increase X4 increase Predicted area burned shows large increases in 2050s during peak months. Yue et al., 2013

  20. Parameterization method also reveals a lengthening of wildfire season. observations Predicted number of days of fire season across the Western US. Mean increase is ~3 weeks. future present-day Fire season is defined as those days when daily area burned is larger than 100 ha in at least one grid box. Yue et al., 2013

  21. What about trends in vegetation in the future climate and the issue of reburning? Results from LPJ dynamic vegetation model show relatively little change in vegetation in 2050s atmosphere. We placed fires randomly within each sub-ecoregion to minimize reburning of gridsquares.

  22. How will changing area burned affect air quality? Ensemble of climate models Median area burned Emissions = area burned x fuel consumption x emission factors Future meteorology GEOS-CHEM Global chemistry model Future air quality

  23. Organic particles increase in future atmosphere over the western U.S. in summer, especially during extreme events. D Organic Carbon, OC D Black Carbon, BC Change in summertime mean PM2.5 in ~2050s, relative to present-day. Yue et al., 2013

  24. Organic particles increase in future atmosphere over the western U.S. in summer, especially during extreme events. Cumulative probability of daily mean concentrations of organic particles • Distribution of daily OC concentrations, May-Oct in Rocky Mountains. • Visibility decreases during extreme events from 130 km to 100 km. • These changes are underestimates due to model resolution. 2050s doubling Present-day Yue et al., 2013

  25. What do these increases in wildfire aerosol mean for human health? % area burned % OC particles Ongoing project with Yale will look at health impacts of these increases. Yue et al., 2013

  26. How do we improve fire predictions in S. California? The largest fires in California are associated with Santa Ana events. Fire plumes (Oct. 2007) Composite Santa Ana winds Need finely resolved wind fields to capture Santa Ana in meteorological record. Hughes and Hall (2010)

  27. Area burned Improving predictions of area burned in Southern California. • Divide up California into smaller ecosystems • Use finer grid • Parameterize effects of elevation, population, and Santa Anas. Santa Ana winds are associated with surface pressure anomalies that can be captured by climate models. 1980-2009 fire occurence Surface pressure anomalies Ratio of future area burned to present-day. Area burned increases by 50-100% in Southwest California. R P 2 methods Yue et al., in review

  28. Main findings. • Area burned by wildfires increases 20-170% across the West by the 2050s, depending on the ecosystem. • During peak months, area burned nearly doubles in Eastern Rockies/Great Plains and quadruples in the forested Rockies. • Wildfire season may increase by ~3 weeks in the West in future. • Increased smoke from wildfires may thwart efforts to regulate air quality in coming decades. This is a climate penalty. Wildfires in Quebec the same day. Haze over Boston on May 31, 2010

  29. Seasonality of fires in Southern California South-West Cal. area Fire regions num. fires Central Western Cal. Largest area burned in SW California. October peak associated with the Santa Ana winds, which are underestimated by large scale models as they lack the detailed topography: need large-scale approach Sierra Nevada

  30. New parameterization predicts yearly variability and seasonality in south west California Southwest CA R2=0.64 Seasonality Area burned in ~2050 / Present-day Area burned in Southern California increases 20-100% by 2050s relative to present-day. Two approaches used in each ecoregion. R P R P R Sierra Nevada Central California South westCalifornia Yue et al., 2013

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