Embed Size (px)
Citation preview
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: SF6, some CFCs
Decades: most greenhouse gases: CO2, N2O, . . .
9-10 years: CH4 (methane, precursor to ozone and greenhouse gas)
Days-weeks: O3 (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 0.075 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 2008.
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
wildfirescombustion
soil dustsea salt
..
...
.cycling
ultra-fine(<0.01 mm)
fine(0.01-1 mm)
cloud(1-100 mm)
combustionvolcanoes
agriculturebiosphere
coarse(1-10 mm) scavenging
precursor gases
SO2 -- sulfur dioxideNOx -- nitrogen oxides
Soup of chemical reactions
NOxNOx
NOx
NOxNOx
VOCs
VOCsVOCs
VOCsVOCs
SO2
NH3
SO2
VOCs -- volatile organic compoundsNH3 -- ammonia
5
Life cycle of particulate matter (PM, aerosols)
nucleation coagulation
condensation
wildfirescombustion
soil dustsea salt
..
...
.cycling
ultra-fine(<0.01 mm)
fine(0.01-1 mm)
cloud(1-100 mm)
combustionvolcanoes
agriculturebiosphere
coarse(1-10 mm) scavenging
precursor gases
Climate change affects many processes.
Soup of chemical reactions
NOxNOx
NOx
NOxNOx
VOCs
VOCsVOCs
VOCsVOCs
SO2
NH3
SO2
Warmer temperatures could increase some emissions.
faster reactions
6
Life cycle of particulate matter (PM, aerosols)
nucleation coagulation
condensation
wildfirescombustion
soil dustsea salt
..
...
.cycling
ultra-fine(<0.01 mm)
fine(0.01-1 mm)
cloud(1-100 mm)
combustionvolcanoes
agriculturebiosphere
coarse(1-10 mm) scavenging
precursor gases
Transport also important!
Soup of chemical reactions
NOxNOx
NOx
NOxNOx
VOCs
VOCsVOCs
VOCsVOCs
SO2
NH3
SO2
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
mg m-3
mg m-3
Racherla and Adams, 2006
Pye et al., 2009
Response of sulfate PM2.5 at the surface to 2000-2050 climate change.
• These model results are computationally expensive.
• How well do models capture variability in present-day PM2.5?
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 EnvironmentVedal et al., 2006
June 8, 2002 June 9, 2002 PM10 = 372 μg/m3
PM2.5 = 200 μg/m3
Standard = 35 µg/m3
PM10 = 40 μg/m3
PM2.5 = 10 μg/m3
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
1970 2000
5 yr means
area burned
obs temperature
1960 2000
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
( ) ( ) a a
dPP z P z dz gdz g
dz
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 fuelB1 = alternative fuelsA1B = 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.
emissionstransportdilutionchemistry
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 boxMeteorology 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 PM2.5 on meteorological variables. Units: μg m-3 D-1 (p-value < 0.05)
Meteorology affects surface concentrations of PM2.5.
Mean PM2.5 is 2.6 μg m-3 greater on a stagnant day
Tai et al. 2010
Observed correlations of PM2.5 with meteorological variables.
1998-2008 meteorology + EPA-AQS observations
Increases in total PM2.5 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.
2000-2050 climate change leads to increases in annual mean PM2.5 across much of the Eastern US.
Change in annual mean PM2.5 concentrations in 2050s relative to present-day
mg 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
1970 2000
Predictions of area burned are made for large eco-regions for the fire season
PNW
ERM
NMS
RMF
DSWCCS
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
Data Fit
Fit depends on relative humidity the previous summerSpracklen et al., 2009; Yue et al., ms.
Calculate emissions
archive met fields from climate model
GEOS-CHEM
Global chemistry model
1950 2000 2025 2050 2075 2100
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 2045-2054, 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 2050. 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 ShrubDSW, Desert Southwest NMS, Nevada /Semi-desert RMF, Rocky Mountain ForestERM, 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.
1986-2000 2051-2065
spread of models
Obs
Median of models
1986 2065
Area
bur
ned
(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
Rat
io o
f 20
50s
/ p
rese
nt-
day
Ratio of 2050s area burned / present-day area burned
Pacific N
orthwest
Desert
Southwest
Nevada M
ountains
Rocky M
ountains
Easte
rn Rock
ies
Californ
ia Coastal S
hrub
median
Fo
rest
Fo
rest
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. firesarea
New parameterization predicts yearly variability and seasonality in south west California
Area burned in Southern California increases 20-100% by 2050s relative to present-day.
Yue et al., ms.
R2=0.64
Southwest CA
Seasonality
Area burned in ~2050 / Present-day
R P R PR
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
Annual DJF JJA
