The Sensitivity of U.S. Surface Ozone Formation to NO x and VOCs as Viewed from Space: the Ozone Monitoring Instrument (OMI) Bryan Duncan 1 , Yasuko Yoshida 1 , Jennifer Olson 2 , Sandy Sillman 3 , Christian Retscher 1 , Ken Pickering 1 , Randall Martin 4 , Ed Celarier 1 , Jim Crawford 2 1 NASA Goddard Space Flight Center 2 NASA Langley Research Center 3 University of Michigan 4 Dalhousie University October 20, 2009, CMAS meeting, North Carolina
Transcript
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 Center2NASA Langley Research Center
3University of Michigan4Dalhousie University
October 20, 2009, CMAS meeting, North Carolina
NOx + VOCs → Ozone
Main Ingredient in Smog
OMINO2
OMIHCHO
h
SO2 NO2HCHOCOO3
Ozone has little vertical variation.
Which reactant is the limiting reagent that controls ozone production?
NOx + VOCs → Ozone
OMI HCHO/NO2: Air Quality Indicator*
• 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.
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NOTE: HCHO/NO2 gives info on the sensitivity of instantaneous ozone production, not the ozone concentration!
*Based on Sillman [1995]Martin et al. [2004]
OMI HCHO/NO2 : August 2006
VOC controls O3 prod. NOx controls O3 production
Lots of Isoprene =NOx controls
Low VOCs =VOC controls
Transition is “fuzzy”: ~1.2-2.2!
NOx – limited regimeVOC – limited regime
VOC controls O3 prod. NOx controls O3 production
OMI HCHO/NO2 : August 2006
Southwest US Northeast US
LA
SanFrancisco
Las Vegas
CentralValley
Toronto
DCPhilly
NYC
Richmond
Boston
Phoenix
OMI captures gradient from downtown to suburbs to rural areas!
Min Ratio Max Ratio
Minimum & Maximum Ratios of 9 Summer Months
The ratio is increasing as NOx emissions decrease. Therefore, ozone formation is becoming more NOx-limited.
Variability Associated with NOx Emissions
June-August OMI NO2: 2007-2005
Wildfires in2007
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.
Variability Associated with Isoprene
Therefore, ozone formation should be more NOx-limited during high ozone events.
But, NOx emissions decreasing!
Isoprene emissions and, subsequently, HCHO increase with temperature.
Therefore, HCHO/NO2 should increase with temperature.
We know that high O3 events increase with temperature.
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!
Extra Slides
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
Instantaneous Ozone Production Rate (x107 molec/cm3-s) vs HCHO/NO2
Transition: HCHO/NO2 ~1.2-2.2
Transition: HCHO/NO2 1.4-2.6
(for NO2 columns > 2.5x1015 molec/cm2)
Assume Transition= 1
NASA Langley box model output. (Provided by Jennifer Olson)
CMAQ
CMAQ
CMAQ 4 km2 horizontal resolutionover Southern California. (Provided by Yongtao Hu, Georgia Tech)
How do tropospheric and PBL columns (x1015 molec/cm2) compare?
1:1
How does the Instantaneous O3 Production Rate vary with the PBL column (x1015 molec/cm2), [HCHO], and [NO2]?
CMAQ 4 km2 horizontal resolutionover Southern California. (Provided by Yongtao Hu, Georgia Tech)
NASA Langley box model output. (Provided by Jennifer Olson)
OMI HCHO as Proxy for Variability of Isoprene Emissions
