Forecasting fine particulate matter (PM2.5) across the United States in a changing climate Loretta J. Mickley Wildfires in Quebec the same day. Haze over Boston on May 31, 2010 Dominick Spracklen, Jennifer A. Logan, Xu Yue, Amos P.K.A. Tai, Daniel J. Jacob, Rynda C. Hudman

2 Atmospheric chemistry examines the mix of gases and particles in the atmosphere: Chemical reactions Distributions in the atmosphere Effects on climate and health Effects of climate on smog Lifetimes in atmospheric chemistry Centuries: SF 6, some CFCs Decades: most greenhouse gases: CO 2, N 2 O, years: CH 4 (methane, precursor to ozone and greenhouse gas) Days-weeks: O 3 (ozone), particulate matter (PM, aka aerosols) Seconds: OH, NO Pollution over Hong Kong Air pollution over Hong Kong reached dangerous levels one of every eight days in 2009

Surface ozone and particulate matter are harmful to human health. Calculated with standard of ppm. Proposed new standards will push more areas into non-attainment. Number of people living in areas that exceed the national ambient air quality standards (NAAQS) in Bars on barplot will change with changing emissions of ozone precursors. Climate change could also change the size of these bars, by changing the day- to-day weather.

4 Life cycle of particulate matter (PM, aerosols) nucleation coagulation condensation wildfires combustion soil dust sea salt cycling ultra-fine (<0.01  m) fine (  m) cloud (1-100  m) combustion volcanoes agriculture biosphere coarse (1-10  m) scavenging precursor gases SO 2 -- sulfur dioxide NOx -- nitrogen oxides Soup of chemical reactions NOx VOCs SO 2 NH 3 SO 2 VOCs -- volatile organic compounds NH 3 -- ammonia

5 Life cycle of particulate matter (PM, aerosols) nucleation coagulation condensation wildfires combustion soil dust sea salt cycling ultra-fine (<0.01  m) fine (  m) cloud (1-100  m) combustion volcanoes agriculture biosphere coarse (1-10  m) scavenging precursor gases Climate change affects many processes. Soup of chemical reactions NOx VOCs SO 2 NH 3 SO 2 Warmer temperatures could increase some emissions. faster reactions

6 Life cycle of particulate matter (PM, aerosols) nucleation coagulation condensation wildfires combustion soil dust sea salt cycling ultra-fine (<0.01  m) fine (  m) cloud (1-100  m) combustion volcanoes agriculture biosphere coarse (1-10  m) scavenging precursor gases Transport also important! Soup of chemical reactions NOx VOCs SO 2 NH 3 SO 2 Warmer temperatures push equilibrium toward gas phase. evaporation faster reactions

Coming climate change will likely affect PM2.5 concentrations. Models disagree on the sign and the magnitude of the impacts  g m -3 Racherla and Adams, 2006 Pye et al., 2009 Response of sulfate PM 2.5 at the surface to climate change. These model results are computationally expensive. How well do models capture variability in present-day PM 2.5 ? A2 A1 We need a simple tool that will allow AQ managers to readily calculate the climate penalty for PM2.5 air quality across a range of models and scenarios. 7

 Hayman fire, June 8-22, 2002  56,000 ha burned  30 miles from Denver and Colorado Springs Colorado Dept. of Public Health and Environment Vedal et al., 2006 June 8, 2002 June 9, 2002 PM 10 = 372 μg/m 3 PM 2.5 = 200 μg/m 3 Standard = 35 µg/m 3 PM 10 = 40 μg/m 3 PM 2.5 = 10 μg/m 3 Worst ever air quality in Denver Effects of wildfires on air quality in cities in Western US

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

First, a few slides on chemistry + climate models. Two constellations of studies 1.Sensitivity of PM2.5 to changing meteorology in the East. 2.Sensitivity of wildfires to changing climate in the West and the consequences for PM2.5.

11 Basic working of climate models All climate models depend on basic physics to describe motions and thermodynamics of the atmosphere: E.g., vertical structure of pressure is described by hydrostatic equation Climate models also depend on parameterizations for many processes. E.g., microphysics of cloud droplet formation, vegetation processes. Tilt of earth, geography, greenhouse gas content Weather + Climate Input Physics + Parameterized processes Climate model Output

Simulations of future climate depend on the path of socio-economic development. Different scenarios follow different socio- economic paths for developed and developing countries. IPCC 2007 Global mean surface temperature anomalies A2 = heavy fossil fuel B1 = alternative fuels A1B = mix of fossil + alternative fuels

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

14 How 3-D chemistry models work. emissions transport dilution chemistry particulate matter (PM) and ozone pollution population GEOS-Chem chemical transport model: Global 3-D model describes the transport and chemical evolution of atmospheric pollutants winds Winds carry pollutants to other boxes. Emissions + chemistry calculated within box Meteorology from a climate model

Two constellations of studies 1.Sensitivity of PM2.5 to changing meteorology in the East. 2.Sensitivity of wildfires to changing climate in the West and the consequences for PM2.5.

Surface ozone levels are sensitive to cold-front passage. Are particles also sensitive to cold-front passage? Leibensperger et al., 2008

Multiple linear regression coefficients for total PM 2.5 on meteorological variables. Units: μg m -3 D -1 (p-value < 0.05) Meteorology affects surface concentrations of PM 2.5. Mean PM 2.5 is 2.6 μg m -3 greater on a stagnant day Tai et al Observed correlations of PM 2.5 with meteorological variables meteorology + EPA- AQS observations Increases in total PM 2.5 on a stagnant day vs. a non- stagnant day. 17

We used Principal Component Analysis to define the main meteorological modes driving PM2.5 variability over the US. Models show increased duration of stagnation in the East, with corresponding increases in annual mean PM2.5. This approach could provide a useful tool to assess climate penalty on PM2.5. We use observed relationships + climate models, no chemistry models climate change leads to increases in annual mean PM 2.5 across much of the Eastern US. Change in annual mean PM 2.5 concentrations in 2050s relative to present-day  g m -3 Tai et al., ms.

How do we predict fires in a future climate? We don’t have a good mechanistic approach for modeling wildfires. Relationship between observed meteorology + area burned + Future meteorology Future area burned

Predictions of area burned are made for large eco-regions for the fire season PNW ERM NMS RMF DSW CCS Ecoregions are aggregates of those in Bailey et al. (1994) In each region, identify the meteorological variables that best predict area burned using stepwise linear regression. We find that the most important predictors for wildfires in the West are temperature, relative humidity, and precipitation.

Regression matches observed area burned, except for California coastal shrub DataFit Fit depends on relative humidity the previous summer Spracklen et al., 2009; Yue et al., ms.

Calculate emissions archive met fields from climate model GEOS-CHEM Global chemistry model GISS climate model Spin-up changing greenhouse gases (A1B scenario) Predict Area Burned Area Burned Regressions GISS GCM meteorological output used to project future area burned, emissions and changes in air quality 50% increase in biomass consumption by wildfires over the western United States for , relative to present-day.

Effect of future fires in a future climate on organic carbon in the western U.S. Change in organic carbon (OC) by 2050s, relative to present-day (5 year mean) Organic carbon particles increase by 40% by Black carbon increases by 20%. For OC, most of increase is from fire emissions, some is from higher biogenic emissions in a warmer climate. Spracklen et al., JGR, 2009 May-October change in OC

Results shown so far were driven by one climate model. But models show large variation in response to changing greenhouse gases. PNW, Pacific Northwest CCS, California Coastal Shrub DSW, Desert Southwest NMS, Nevada /Semi-desert RMF, Rocky Mountain Forest ERM, East Rockies/ Plains. CCS PNW NMS DSW RMF ERM Temp Precip Rel Humidity Results from IPCC AR4 ensemble of climate models: warmer, drier, less humid. Changes in meteorology by 2050s, relative to present-day, for JJA Yue et al., ms.

Wildfires in western US are predicted to increase by ~60% by 2050s. The GCMs cannot match year to year variability, but match the mean area burned fairly well in present-day. Yue et al., ms spread of models Obs Median of models Area burned (ha) +40% +60% +70% +60% +20% doubling CCS PNW NMS DSW RMF ERM

Median GCM results show an increase in area burned in all regions. Yue et al., ms. CCS PNW NMS DSW RMF ERM Ratio of 2050s / present-day Ratio of 2050s area burned / present-day area burned Pacific Northwest Desert Southwest Nevada Mountains Rocky Mountains Eastern Rockies California Coastal Shrub median Forest Median changes: 40-70% increase in forested regions 60% increase in grasslands Doubling in Southwest

Yue et al., ms. Organic particles increase in future atmosphere over the western U.S. in summer, especially during extreme events. Change in OC in ~2050s, relative to present-day Cumulative probability of daily mean concentrations of organic particles 2050s Present- day doubling Rocky Mountains April-October.

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

Fire data from a suite of sources. Yue et al., ms. Parameterize area burned as function of: Temperature Relative humidity Precipitation Large-scale pressure differences Divide up southern California into 3 smaller ecoregions. Improving predictions of area burned in Southern California. Area burned Surface pressure anomalies

Seasonality of fires in Southern California South-West Cal. Central Western Cal. Sierra Nevada Fire regions 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 num. fires area

New parameterization predicts yearly variability and seasonality in south west California Area burned in Southern California increases % by 2050s relative to present-day. Yue et al., ms. R 2 =0.64 Southwest CA Seasonality Area burned in ~2050 / Present-day R P R South west California Central California Sierra Nevada Two approaches used in each ecoregion.

Conclusions Models show increased duration of stagnation in future atmosphere, with corresponding increases in annual mean PM2.5. Wildfire activity in the West can be predicted with meteorological variables. Area burned by wildfires may double in some regions in the western US by 2050s. By 2050s, mean summertime organic carbon particles could increase 40-70%, with doubling during extreme events.

Future regional predictions for meteorology in A1B 2100 atmosphere show large variation across North America. Percent change in 2100 precipitation relative to present-day Number of models showing increasing precipitation IPCC 2007 most models few models AnnualDJF JJA