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Environ Sci Technol. 2019 Aug 20;53(16):9636-9645. doi: 10.1021/acs.est.9b01769. Epub 2019 Aug 2.

A Multiplatform Inversion Estimation of Statewide and Regional Methane Emissions in California during 2014-2016.

Author information

1
California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States.
2
Department of Civil and Environmental Engineering , Washington State University , Pullman , Washington 99163 , United States.
3
NASA Jet Propulsion Laboratory , California Institute of Technology , Pasadena , California 91109 , United States.
4
Scripps Institution of Oceanography , University of California , San Diego , La Jolla , California 92037 , United States.
5
Earth Science Division , NASA Ames Research Center , Moffett Field , California 94035 , United States.
6
Japan Weather Association , Tokyo , Japan.
7
Department of Physics , University of Michigan , Ann Arbor , Michigan 48109 , United States.
8
Physical Sciences Division , NOAA Earth System Research Laboratory , Boulder , Colorado 80305 , United States.
9
The Cooperative Institute for Research in Environmental Sciences , University of Colorado Boulder , Boulder , Colorado 80305 , United States.
10
Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.

Abstract

California methane (CH4) emissions are quantified for three years from two tower networks and one aircraft campaign. We used backward trajectory simulations and a mesoscale Bayesian inverse model, initialized by three inventories, to achieve the emission quantification. Results show total statewide CH4 emissions of 2.05 ± 0.26 (at 95% confidence) Tg/yr, which is 1.14 to 1.47 times greater than the anthropogenic emission estimates by California Air Resource Board (CARB). Some of differences could be biogenic emissions, superemitter point sources, and other episodic emissions which may not be completely included in the CARB inventory. San Joaquin Valley (SJV) has the largest CH4 emissions (0.94 ± 0.18 Tg/yr), followed by the South Coast Air Basin, the Sacramento Valley, and the San Francisco Bay Area at 0.39 ± 0.18, 0.21 ± 0.04, and 0.16 ± 0.05 Tg/yr, respectively. The dairy and oil/gas production sources in the SJV contribute 0.44 ± 0.36 and 0.22 ± 0.23 Tg CH4/yr, respectively. This study has important policy implications for regulatory programs, as it provides a thorough multiyear evaluation of the emissions inventory using independent atmospheric measurements and investigates the utility of a complementary multiplatform approach in understanding the spatial and temporal patterns of CH4 emissions in the state and identifies opportunities for the expansion and applications of the monitoring network.

PMID:
31347357
DOI:
10.1021/acs.est.9b01769

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