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Towards sector-based attribution using intra-city variations in satellite-based emission ratios between CO₂ and CO

Wu, Dien and Liu, Junjie and Wennberg, Paul O. and Palmer, Paul I. and Nelson, Robert R. and Kiel, Matthäus and Eldering, Annmarie (2022) Towards sector-based attribution using intra-city variations in satellite-based emission ratios between CO₂ and CO. Atmospheric Chemistry and Physics, 22 (22). pp. 14547-14570. ISSN 1680-7324. doi:10.5194/acp-22-14547-2022.

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Carbon dioxide (CO₂) and air pollutants such as carbon monoxide (CO) are co-emitted by many combustion sources. Previous efforts have combined satellite-based observations of multiple tracers to calculate their emission ratio (ER) for inferring combustion efficiency at the regional to city scale. Very few studies have focused on combustion efficiency at the sub-city scale or related it to emission sectors using space-based observations. Several factors are important for interpreting and deriving spatially resolved ERs from asynchronous satellite measurements, including (1) variations in meteorological conditions given the mismatch in satellite overpass times, (2) differences in vertical sensitivity of the retrievals (i.e., averaging kernel profiles), (3) interferences from the biosphere and biomass burning, and (4) the mismatch in the daytime variations of CO and CO₂ emissions. In this study, we extended an established emission estimate approach to arrive at spatially resolved ERs based on retrieved column-averaged CO₂ (XCO₂) from the Snapshot Area Mapping (SAM) mode of the Orbiting Carbon Observatory-3 (OCO-3) and column-averaged CO from the TROPOspheric Monitoring Instrument (TROPOMI). To evaluate the influences of the confounding factors listed above and further attribute intra-urban variations in ERs to certain sectors, we leveraged a Lagrangian atmospheric transport model with an urban land cover classification dataset and reported ER_(CO) values from the sounding level to the overpass and city level. We found that the differences in overpass times and averaging kernels between OCO and TROPOMI strongly affect the estimated spatially resolved ER_(CO). Specifically, a time difference of >3 h typically led to dramatic changes in wind directions and urban plume shapes, thereby making the calculation of accurate sounding-specific ERCO difficult. After removing such cases from consideration and applying a simple plume shift method when necessary to account for changes in wind direction and speed, we discovered significant contrasts in combustion efficiencies between (1) two megacities versus two industry-oriented cities and (2) different regions within a city, based on six nearly coincident overpasses per city. Results suggest that the ER_(CO) impacted by heavy industry in Los Angeles is slightly lower than the overall city-wide value (<10 ppb-COppm-CO₂). In contrast, the ER_(CO) related to heavy industry in Shanghai is much higher than Shanghai's city mean and more aligned with the city means of two selected industry-oriented cities in China (approaching 20 ppb-COppm-CO₂). Although investigations based on a larger number of satellite overpasses are needed, our unique approach (i.e., without using sector-specific information from emission inventories) provides new insights into assessing combustion efficiency within a city from future satellite missions, such as those that will map column CO₂ and CO concentrations simultaneously with high spatiotemporal resolutions.

Item Type:Article
Related URLs:
URLURL TypeDescription
Wu, Dien0000-0002-2915-5335
Liu, Junjie0000-0002-7184-6594
Wennberg, Paul O.0000-0002-6126-3854
Palmer, Paul I.0000-0002-1487-0969
Nelson, Robert R.0000-0002-3471-5683
Kiel, Matthäus0000-0002-9784-962X
Eldering, Annmarie0000-0003-1080-9922
Additional Information:The production of the OCO-3 science data products used in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (prime contract number 80NM0018D0004). The research effort was funded by the Jet Propulsion Laboratory Research and Technology Development project R.21.023.106. The analysis was supported by the W. M. Keck Institute for Space Studies and by the National Aeronautics and Space Administration (grant no. 80NSSC21k1064).
Group:Division of Geological and Planetary Sciences
Funding AgencyGrant Number
JPL Research and Technology Development FundR.21.023.106
Issue or Number:22
Record Number:CaltechAUTHORS:20221128-494241100.8
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:118053
Deposited By: Research Services Depository
Deposited On:08 Dec 2022 16:36
Last Modified:08 Dec 2022 17:15

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