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Quantifying the loss of processed natural gas within California's South Coast Air Basin using long-term measurements of ethane and methane

Wunch, Debra and Toon, Geoffrey C. and Hedelius, Jacob K. and Vizenor, Nicholas and Roehl, Coleen M. and Saad, Katherine M. and Blavier, Jean-François L. and Blake, Donald R. and Wennberg, Paul O. (2016) Quantifying the loss of processed natural gas within California's South Coast Air Basin using long-term measurements of ethane and methane. Atmospheric Chemistry and Physics, 16 (22). pp. 14091-14105. ISSN 1680-7324.

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Methane emissions inventories for Southern California's South Coast Air Basin (SoCAB) have underestimated emissions from atmospheric measurements. To provide insight into the sources of the discrepancy, we analyze records of atmospheric trace gas total column abundances in the SoCAB starting in the late 1980s to produce annual estimates of the ethane emissions from 1989 to 2015 and methane emissions from 2007 to 2015. The first decade of measurements shows a rapid decline in ethane emissions coincident with decreasing natural gas and crude oil production in the basin. Between 2010 and 2015, however, ethane emissions have grown gradually from about 13 ± 5 to about 23 ± 3 Gg yr⁻¹, despite the steady production of natural gas and oil over that time period. The methane emissions record begins with 1 year of measurements in 2007 and continuous measurements from 2011 to 2016 and shows little trend over time, with an average emission rate of 413 ± 86 Gg yr⁻¹. Since 2012, ethane to methane ratios in the natural gas withdrawn from a storage facility within the SoCAB have been increasing by 0.62 ± 0.05 % yr⁻¹, consistent with the ratios measured in the delivered gas. Our atmospheric measurements also show an increase in these ratios but with a slope of 0.36 ± 0.08 % yr⁻¹, or 58 ± 13 % of the slope calculated from the withdrawn gas. From this, we infer that more than half of the excess methane in the SoCAB between 2012 and 2015 is attributable to losses from the natural gas infrastructure.

Item Type:Article
Related URLs:
URLURL TypeDescription
Wunch, Debra0000-0002-4924-0377
Toon, Geoffrey C.0000-0003-4174-7541
Hedelius, Jacob K.0000-0003-2025-7519
Roehl, Coleen M.0000-0001-5383-8462
Saad, Katherine M.0000-0002-2501-6223
Wennberg, Paul O.0000-0002-6126-3854
Additional Information:© Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License. Received: 26 Apr 2016 – Discussion started: 17 May 2016 – Revised: 13 Sep 2016 – Accepted: 18 Oct 2016 – Published: 15 Nov 2016. Part of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. We thank the various people who have assisted with MkIV ground-based observations over the years, as well as the NASA Upper Atmosphere Research Program for funding. This research was supported by NASA’s Carbon Cycle Science program (NNX14AI60G). TCCON data were obtained from the TCCON Data Archive, hosted by the Carbon Dioxide Information Analysis Center (CDIAC) – We thank four anonymous reviewers and D. Lyon for providing thoughtful reviews that significantly improved this paper. Data availability. TCCON data are available from the TCCON data archive, hosted by CDIAC: Each TCCON dataset used in this paper is cited independently. The JPL MkIV FTS data are available from the webpage Edited by: R. Volkamer. Reviewed by: four anonymous referees.
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Issue or Number:22
Record Number:CaltechAUTHORS:20200529-093434423
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Official Citation:Wunch, D., Toon, G. C., Hedelius, J. K., Vizenor, N., Roehl, C. M., Saad, K. M., Blavier, J.-F. L., Blake, D. R., and Wennberg, P. O.: Quantifying the loss of processed natural gas within California's South Coast Air Basin using long-term measurements of ethane and methane, Atmos. Chem. Phys., 16, 14091–14105,, 2016.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103564
Deposited By: George Porter
Deposited On:29 May 2020 18:08
Last Modified:29 May 2020 18:08

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