National Center for Atmospheric Research

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Impacts of the Fall 2007 California Wildfires on
Surface Ozone Integrating Local Observations
with Global Model Simulations
G. Pfister, C. Wiedinmyer, L. Emmons, D. Edwards

• National Center for Atmospheric Research
• Atmospheric Chemistry Division
• Boulder, CO

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Study Outlook
Goal - Quantify the contribution of wildfires to
surface ozone AQ Wildfires are a source of ozone
precusors emissions and in addition to transport
and industry might be additional contributors to
ozone pollution.
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Study Outlook
Goal - Quantify the contribution of wildfires to
surface ozone AQ Wildfires are a source of ozone
precusors emissions and in addition to transport
and industry might be additional contributors to
ozone pollution. Case - Fires In California
in Fall 2007 Severe drought conditions and hot
weather contributed to an extremely intense late
fire season. Fires in October were the most
destructive of the year (500,000 acres burned).
Nationwide, California is one of the states
with the highest wildfire activity. In 2007,
wildland fires burned about 9 million acres
across the US with California accounting for 10
of the acres burned Source
www.nifc.gov/fire_info/fire_stats.htm
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Technique
Combined analysis of Surface O3 from
US EPA Air Quality System Data Mart Internet
Database. Accessed Feb, 2008. Special Thanks to
Nick Mangus for help with data access.
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Technique
Combined analysis of Surface O3 from Model
for OZone and Related Chemical Tracers Offline
Chemistry Transport Model (CTM) T85 (1.4 x 1.4
deg) driven by NCEP/GFS fields, hourly
output
US EPA Air Quality System Data Mart Internet
Database. Accessed Feb, 2008. Special Thanks to
Nick Mangus for help with data access.
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Technique
Combined analysis of Surface O3 from Model
for OZone and Related Chemical Tracers Offline
Chemistry Transport Model (CTM) T85 (1.4 x 1.4
deg) driven by NCEP/GFS fields, hourly
output
Fire Emissions MODIS thermal anomalies
(locationTime) Vegetation data Emission
factors
US EPA Air Quality System Data Mart Internet
Database. Accessed Feb, 2008. Special Thanks to
Nick Mangus for help with data access.
Wiedinmyer, C., et al. (2006), Atmos. Environ.,
40, 3419-3432.
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Technique
Combined analysis of Surface O3 from Model
for OZone and Related Chemical Tracers Offline
Chemistry Transport Model (CTM) T85 (1.4 x 1.4
deg) driven by NCEP/GFS fields, hourly
output Model Tracers COFIRE - keeps
track of the amount of CO emitted from the fires
O3FIRE - keeps track of the O3 production
from NO emitted from the fires
Fire Emissions MODIS thermal anomalies
(locationTime) Vegetation data Emission
factors
US EPA Air Quality System Data Mart Internet
Database. Accessed Feb, 2008. Special Thanks to
Nick Mangus for help with data access.
Wiedinmyer, C., et al. (2006), Atmos. Environ.,
40, 3419-3432.
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Regional Impact
The region of maximum impact of COFIRE does not
necessarily co-locate with the maximum in O3FIRE
CO directly emitted gt maximum impact
occurs right over the source region O3
chemically produced from fire-emitted precursors
gt impact is shifted downwind of the source
region, distance depends on transport
times and chemical regime
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Quantifying Fire Impact
Rural Sites Mean observed (modeled) enhancement
for O3FIRE gt 20 ppb 12 ? 14 ppb (10 ? 10 ppb)
September 10 ? 13 ppb (12 ? 9 ppb)
October
8-hour afternoon concentrations
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Chemistry
NO2FIRE and O3FIRE Relationship for different
NOx regimes
Adding additional NOx in a less polluted
environment causes a larger ozone increase
compared to a NOx and VOC richer environment
Data set limited to September and local afternoon
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AQ Considerations
Exceedances of 80 ppb standard 5 O3FIRE lt 1
ppb 11 O3FIRE gt 1 ppb
Violations of standards in rural areas estimated
as three times more likely because of pollution
from wildfires.
Exceedances of 75 ppb standard 9 O3FIRE lt
1 ppb 17 O3FIRE gt 1 ppb
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AQ Considerations
Exceedances of 80 ppb standard 5 O3FIRE lt 1
ppb 11 O3FIRE gt 1 ppb 17 O3FIRE gt
5 ppb
Violations of standards in rural areas estimated
as three times more likely because of pollution
from wildfires.
Exceedances of 75 ppb standard 9 O3FIRE lt
1 ppb 17 O3FIRE gt 1 ppb 32 O3FIRE gt
5 ppb
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Summary

• Extract impact of fires on surface O3 from local
  observations using a global CTM with CO and O3
  fire tracer
• Clear increase in observed O3 when the model
  predicts a strong impact of pollution from the
  fires (average 10 ppb)
• Violations of standards in rural areas estimated
  as three times more likely because of pollution
  from wildfires
• Fires can cause violations of standards to happen
  during photochemically less active seasons
• The study demonstrates the far-reaching impact of
  O3 pollution from the fires

Limitation of this study Model Resolution
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Summary ? Outlook

• Global CTM(MOZART)
• Regional CTM (WRF-Chem)
• Targeting Model consistencyin chemistry and
  emissions

large scale transport andprocesses, inflow
small scale processes,local effects
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Summary ? Outlook

• Global CTM(MOZART)
• Regional CTM (WRF-Chem)
• Targeting Model consistencyin chemistry and
  emissions

large scale transport andprocesses, inflow
small scale processes,local effects
Preliminary Model Results Surface Data provided
by US EPA Air Quality System Data Mart internet
database.
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Outlook

• Case Study Summer 2008 Fires in CA
• 1,157,930 acres burned with over 2,780 individual
  fires (at the series height). Majority of the
  fires started after June 20, some earlier fires
  started on June 6.

MOZART COFIRE overlaid by number of days when O3
standards were violated at surface monitoring
sites
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Outlook

• Case Study Summer 2008 Fires in CA
• 1,157,930 acres were burned with over 2,780
  individual fires (at the series height).
  Majority of the fires started on June 20, some
  earlier fires started on June 6.
• NASA ARCTAS/CARB field campaign in June 2008
  provides additional observations for model
  evaluation and analysis.

Aircaft data provided by Eric Apel, NCAR
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Thanks !