The Sensitivity of U'S' Surface Ozone Formation to NOx and VOCs as Viewed from Space: the Ozone Moni

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The Sensitivity of U.S. Surface Ozone Formation
to NOx and VOCs as Viewed from Space the Ozone
Monitoring Instrument (OMI)

• Bryan Duncan1, Yasuko Yoshida1, Jennifer Olson2,
• Sandy Sillman3, Christian Retscher1, Ken
  Pickering1, Randall Martin4, Ed Celarier1, Jim
  Crawford2
• 1NASA Goddard Space Flight Center
• 2NASA Langley Research Center
• 3University of Michigan
• 4Dalhousie University

October 20, 2009, CMAS meeting, North Carolina
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OMI HCHO/NO2 Air Quality Indicator
Based on Sillman 1995 Martin et al. 2004
hv
NOx VOCs ? Ozone
If HCHO/NO2 is low then one must reduce
anthropogenic VOCs to lower ozone. If
HCHO/NO2 is high then one must reduce NOx to
lower ozone.
NOTE HCHO/NO2 gives info on the sensitivity of
instantaneous ozone production, not the ozone
concentration!
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OMI HCHO/NO2 August 2006
Lots of Isoprene NOx controls
Low VOCs VOC controls
VOC controls O3 prod.
NOx controls O3 production
NOx limited regime
VOC limited regime
Transition is fuzzy 1.2-2.2!
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OMI HCHO/NO2 August 2006
Southwest US
Northeast US
Toronto
Las Vegas
Boston
Central Valley
Phoenix
NYC
San Francisco
Philly
DC
LA
Richmond
VOC controls O3 prod.
NOx controls O3 production
OMI captures gradient from downtown to suburbs to
rural areas!
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Minimum Maximum Ratios of 9 Summer Months
Min Ratio
Max Ratio
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Variability Associated with NOx Emissions
The ratio is increasing as NOx emissions
decrease. Therefore, ozone formation is becoming
more NOx-limited.
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June-August OMI NO2 2007-2005
Wildfires in 2007
Point sources 10 lower in 2007 due to NOx Budget
Trading Program of EPA. Automobile emissions
decreased due to Tier 2 Vehicle and Gasoline
Sulfur Program.
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Variability Associated with Isoprene
Isoprene emissions and, subsequently, HCHO
increase with temperature. Therefore, HCHO/NO2
should increase with temperature. We know that
high O3 events increase with temperature.
Therefore, ozone formation should be more
NOx-limited during high ozone events.
But, NOx emissions decreasing!
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Conclusions

• The OMI ratio appears to be a credible air
  quality indicator and is consistent with in situ
  observations.
• Ozone production became more NOx-limited over
  the U.S. from 2005-2007 because of substantial
  NOx emission reductions.
• Ozone production should be more NOx-limited
  during heat waves in regions with high biogenic
  emissions.
• The fine horizontal resolution allows us to see
  the gradient in the ratio from urban to suburban
  to rural areas.
• Currently analyzing CMAQ output. Stay tuned!

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Extra Slides
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CMAQ Tropospheric Column HCHO/NO2
4x4 km2 horizontal resolution July 1st 4th
mean in 2007 at 1-2 pm Provided by Yongtao Hu,
Georgia Tech
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Instantaneous Ozone Production Rate (x107
molec/cm3-s) vs HCHO/NO2
(for NO2 columns gt 2.5x1015 molec/cm2)
Transition HCHO/NO2 1.2-2.2
Assume Transition 1
CMAQ
NASA Langley box model output. (Provided by
Jennifer Olson)
Transition HCHO/NO2 1.4-2.6
CMAQ
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How do tropospheric and PBL columns (x1015
molec/cm2) compare?
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CMAQ 4 km2 horizontal resolution over Southern
California. (Provided by Yongtao Hu, Georgia
Tech)
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How does the Instantaneous O3 Production Rate
vary with the PBL column (x1015 molec/cm2),
HCHO, and NO2?
CMAQ 4 km2 horizontal resolution over Southern
California. (Provided by Yongtao Hu, Georgia
Tech) NASA Langley box model output. (Provided
by Jennifer Olson)
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OMI HCHO as Proxy for Variability of Isoprene
Emissions
Major player in AQ!
22 Variation