observing u.s. urban no x emissions from ozone monitoring instrument (omi) satellite retrievals...
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Observing U.S. urban NOx emissions from Ozone Monitoring Instrument (OMI) satellite retrievals
Zifeng Lu, David G. Streets
Decision and Information Sciences DivisionArgonne National Laboratory
Presented at AQAST 6 Meeting
Rice University, Houston, TXJanuary 15-17, 2014
Zifeng Lu, Observing US urban NOx emissions from OMI satellite retrievalsAQAST 6 Meeting, Rice University, Houston, TX, January 15, 2014
Introduction
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Our previous efforts on emissions estimation from satellite retrievals– Power plants in China
• NOx emissions Zhang et al., 2009; Wang et al., 2010; Wang et al., 2012
• SO2 emissions Li et al., 2010
– Power plants in India• NOx emissions Lu and Streets, 2012
• SO2 emissions Lu et al., 2013
– Power plants in US• NOx emissions Duncan et al., 2013
Good agreement between satellite observations and bottom-up emissions for areas dominated by power plant emissions
This work NOx emissions from US urban areas
Problem to be solved
Is it possible to use OMI NO2 retrievals to estimate the NOx emissions from US urban areas?
If so, how accurate are the estimates?
Zifeng Lu, Observing US urban NOx emissions from OMI satellite retrievalsAQAST 6 Meeting, Rice University, Houston, TX, January 15, 2014
Processing OMI NO2 Level 2 Data
OMI NO2 tropospheric vertical columns
– Berkeley High-Resolution (BEHR) retrievals v2.0A (2005-2011)Russell et al., 2011, 2012
– NASA Standard Product (NASA SP) v2.1 collection 3 (2005-2013)Boersma et al., 2011; Bucsela et al., 2013
Filters– Solar zenith angle < 70 degree– Cloud fraction < 0.2– Terrain reflectivity < 0.3– Cross track positions 11-50 (1-based)– Dynamically filter OMI anomaly pixels and error pixels using
XtrackQualityFlags and VCDQualityFlags
Additional– Only summertime data (i.e., May to August) – Oversampling to a 2 km x 2 km grid
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Zifeng Lu, Observing US urban NOx emissions from OMI satellite retrievalsAQAST 6 Meeting, Rice University, Houston, TX, January 15, 2014
Decrease of OMI NO2 over US
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BEHRSummer 2005
BEHRSummer 2011
NASA SPSummer 2005
NASA SPSummer 2013
Summertime BEHR OMI NO2 (2005 vs. 2011)
Summertime NASA SP OMI NO2 (2005 vs. 2013)
Zifeng Lu, Observing US urban NOx emissions from OMI satellite retrievalsAQAST 6 Meeting, Rice University, Houston, TX, January 15, 2014
Selection of Urban Areas
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– Examine the top 80 urban areas on the basis of population– Combine the adjacent urban areas sharing the same NO2 hotspot
– Exclude some urban areas, the NO2 signals of which are not isolated
51 urban areas– ~40% of the total NOx emissions in the US
NASA SPSummer 2005-2013
Zifeng Lu, Observing US urban NOx emissions from OMI satellite retrievalsAQAST 6 Meeting, Rice University, Houston, TX, January 15, 2014
Fitting OMI NO2 hot spots with 2-D Gaussian function
Fioletov et al., GRL, 2011; Lu et al., EST, 2013
Since , the parameter physically means the total
number of NO2 molecules observed (or the observed NO2 burden).
Unit of is molecules, mass units
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Zifeng Lu, Observing US urban NOx emissions from OMI satellite retrievalsAQAST 6 Meeting, Rice University, Houston, TX, January 15, 2014
Example: Chicago
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1 2 3 4 5 6 7 8 9Emissions (kg/h/grid)
-90 -70 -50 -30 -10 10 30 50 70 90% Difference
1 2 3 4 5 6 7 8 9OMI NO2 (1015 molecules/cm2)
Urban Area OMI BEHR 2005 2-D Gaussian Fit % Difference NOx Emissions
Emission inventory
Power plants CEMSBiomass burning GFED3.1Other Xing et al., 2013
Zifeng Lu, Observing US urban NOx emissions from OMI satellite retrievalsAQAST 6 Meeting, Rice University, Houston, TX, January 15, 2014
Example: Houston
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1 2 3 4 5 6 7 8 9Emissions (kg/h/grid)
-90 -70 -50 -30 -10 10 30 50 70 90% Difference
1 2 3 4 5 6 7 8 9OMI NO2 (1015 molecules/cm2)
Urban Area OMI NASA SP 2005 2-D Gaussian Fit % Difference NOx Emissions
Zifeng Lu, Observing US urban NOx emissions from OMI satellite retrievalsAQAST 6 Meeting, Rice University, Houston, TX, January 15, 2014
NOx emissions vs. OMI NO2 burden
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Good agreement between NOx emissions and OMI NO2 observations
Berkeley retrievals are ~30% higher than NASA retrievals over urban areas
The 95% CI of the summertime NO2 lifetime in US urban areas– Berkeley retrievals 2.1~5.6 h NASA retrievals 1.4~4.6 h
Uncertainties of urban NOx emissions estimated from OMI NO2 observations– Berkeley retrievals ±45% NASA retrievals ±57%
Each point represents a yearly fitted result for an urban areaError bars are the 95% CIs of fitted
BEHR NASA SP95% CI: 45% 95% CI: 57%
Zifeng Lu, Observing US urban NOx emissions from OMI satellite retrievalsAQAST 6 Meeting, Rice University, Houston, TX, January 15, 2014
Interannual trend of the sum of fitted OMI NO2 burden for all selected urban areas
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From 2005 to 2011 From 2005 to 2013
Total amount of NO2 observed by the OMI over selected urban areas24% decrease 36% decrease
Total NOx emissions from selected urban areas26% decrease 33% decrease
Averages of annual mean NO2 concentrations in selected urban areas25% decrease 30% decrease
BEHR NASA SP
Conclusions
NASA
Air Quality Applied Sciences Team (AQAST) program
Thank you for your attention!
Questions?Contact
Zifeng Lu [email protected] & David G. Streets [email protected]
Acknowledgements
OMI NO2 retrievals can be used to constrain the trends and estimate the amounts of NOx emissions from urban areas with reasonable accuracy
For a single urban area, the 95% CI of the estimated NOx emission is ±45% for the Berkeley retrievals and ±57% for the NASA retrievals
The total OMI NO2 burden over major US urban areas decreased by >30% from 2005 to 2013, in good agreement with decreases in bottom-up emissions and ground-based measurements