Exploiting OMI NO2 satellite observations to infer fossil-fuel CO2 emissions from U.S. megacities

Daniel L Goldberg; Zifeng Lu; Tomohiro Oda; Lok N Lamsal; Fei Liu; Debora Griffin; Chris A McLinden; Nickolay A Krotkov; Bryan N Duncan; David G Streets

doi:10.1016/j.scitotenv.2019.133805

Exploiting OMI NO₂ satellite observations to infer fossil-fuel CO₂ emissions from U.S. megacities

Sci Total Environ. 2019 Dec 10:695:133805. doi: 10.1016/j.scitotenv.2019.133805. Epub 2019 Aug 8.

Authors

Affiliations

¹ Energy Systems Division, Argonne National Laboratory, Lemont, IL, USA; Consortium for Advanced Science and Engineering, University of Chicago, Chicago, IL, USA. Electronic address: dgoldberg@gwu.edu.
² Energy Systems Division, Argonne National Laboratory, Lemont, IL, USA; Consortium for Advanced Science and Engineering, University of Chicago, Chicago, IL, USA.
³ Goddard Earth Sciences Technology and Research (GESTAR), University Space Research Association, Columbia, MD, USA; Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, MD, USA.
⁴ Goddard Earth Sciences Technology and Research (GESTAR), University Space Research Association, Columbia, MD, USA; Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA.
⁵ Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada.
⁶ Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA.

PMID: 31419680
DOI: 10.1016/j.scitotenv.2019.133805

Abstract

Fossil-fuel CO₂ emissions and their trends in eight U.S. megacities during 2006-2017 are inferred by combining satellite-derived NO_X emissions with bottom-up city-specific NO_X-to-CO₂ emission ratios. A statistical model is fit to a collection NO₂ plumes observed from the Ozone Monitoring Instrument (OMI), and is used to calculate top-down NO_X emissions. Decreases in OMI-derived NO_X emissions are observed across the eight cities from 2006 to 2017 (-17% in Miami to -58% in Los Angeles), and are generally consistent with long-term trends of bottom-up inventories (-25% in Miami to -49% in Los Angeles), but there are some interannual discrepancies. City-specific NO_X-to-CO₂ emission ratios, used to calculate inferred CO₂, are estimated through annual bottom-up inventories of NO_X and CO₂ emissions disaggregated to 1 × 1 km² resolution. Over the study period, NO_X-to-CO₂ emission ratios have decreased by ~40% nationwide (-24% to -51% for our studied cities), which is attributed to a faster reduction in NO_X when compared to CO₂ due to policy regulations and fuel type shifts. Combining top-down NO_X emissions and bottom-up NO_X-to-CO₂ emission ratios, annual fossil-fuel CO₂ emissions are derived. Inferred OMI-based top-down CO₂ emissions trends vary between +7% in Dallas to -31% in Phoenix. For 2017, we report annual fossil-fuel CO₂ emissions to be: Los Angeles 113 ± 49 Tg/yr; New York City 144 ± 62 Tg/yr; and Chicago 55 ± 24 Tg/yr. A study in the Los Angeles area, using independent methods, reported a 2013-2016 average CO₂ emissions rate of 104 Tg/yr and 120 Tg/yr, which suggests that the CO₂ emissions from our method are in good agreement with other studies' top-down estimates. We anticipate future remote sensing instruments - with better spatial and temporal resolution - will better constrain the NO_X-to-CO₂ ratio and reduce the uncertainty in our method.

Keywords: CO(2) emissions; NO(x) emissions; OMI NO(2); Top-down emissions.