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Zifeng Lu, David G. Streets Decision and Information Sciences Division Argonne National Laboratory

Observing U.S . urban NO x emissions from Ozone Monitoring Instrument (OMI) satellite retrievals. Zifeng Lu, David G. Streets Decision and Information Sciences Division Argonne National Laboratory Presented at AQAST 6 Meeting Rice University, Houston, TX January 15-17, 2014.

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Zifeng Lu, David G. Streets Decision and Information Sciences Division Argonne National Laboratory

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  1. 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, TX January 15-17, 2014

  2. Introduction • 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?

  3. 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

  4. Decrease of OMI NO2 over US Summertime BEHR OMI NO2 (2005 vs. 2011) Summertime NASA SP OMI NO2 (2005 vs. 2013) BEHR Summer 2005 BEHR Summer 2011 NASA SP Summer 2005 NASA SP Summer 2013

  5. Selection of Urban Areas • 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 SP Summer 2005-2013

  6. 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

  7. Emission inventory Power plants CEMS Biomass burning GFED3.1 Other Xing et al., 2013 Example: Chicago Urban Area OMI BEHR 2005 2-D Gaussian Fit % Difference NOx Emissions

  8. Example: Houston Urban Area OMI NASA SP 2005 2-D Gaussian Fit % Difference NOx Emissions

  9. NOx emissions vs. OMI NO2burden Each point represents a yearly fitted result for an urban area Error bars are the 95% CIs of fitted  • 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 NOxemissions estimated from OMI NO2 observations • Berkeley retrievals ±45% NASA retrievals ±57% BEHR NASA SP 95% CI: 45% 95% CI: 57%

  10. Interannual trend of the sum of fitted OMI NO2 burden for all selected urban areas BEHR NASA SP From 2005 to 2011 From 2005 to 2013 Total amount of NO2 observed by the OMI over selected urban areas 24% decrease 36% decrease Total NOx emissions from selected urban areas 26% decrease 33% decrease Averages of annual mean NO2 concentrations in selected urban areas 25% decrease 30% decrease

  11. 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 Conclusions Acknowledgements NASA Air Quality Applied Sciences Team (AQAST) program Contact Zifeng Lu zlu@anl.gov& David G. Streets dstreets@anl.gov Thank you for your attention! Questions?

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