A multitower measurement network estimate of California's methane emissions. Issue 19 (3rd October 2013)

• Record Type: Journal Article
• Authors: Jeong, Seongeun; Hsu, Ying‐Kuang; Andrews, Arlyn E.; Bianco, Laura; Vaca, Patrick; Wilczak, James M.; Fischer, Marc L.
• Is Part Of: Journal of geophysical research. Volume 118:Issue 19(2013)
• Page Start: 11, 339
• Page End: 11, 351
• Publication Date: 2013-10-03
• Subjects: Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/jgrd.50854
• Languages: English
• ISSNs: 2169-897X

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>[1] We present an analysis of methane (CH<sub>4</sub>) emissions using atmospheric observations from five sites in California's Central Valley across different seasons (September 2010 to June 2011). CH<sub>4</sub> emissions for spatial regions and source sectors are estimated by comparing measured CH<sub>4</sub> mixing ratios with transport model (Weather Research and Forecasting and Stochastic Time‐Inverted Lagrangian Transport) predictions based on two 0.1° CH<sub>4</sub> (seasonally varying "California‐specific" (California Greenhouse Gas Emission Measurements, CALGEM) and a static global (Emission Database for Global Atmospheric Research, release version 42, EDGAR42)) prior emission models. Region‐specific Bayesian analyses indicate that for California's Central Valley, the CALGEM‐ and EDGAR42‐based inversions provide consistent annual total CH<sub>4</sub> emissions (32.87 ± 2.09 versus 31.60 ± 2.17 Tg CO<sub>2</sub>eq yr<sup>−1</sup>; 68% confidence interval (CI), assuming uncorrelated errors between regions). Summing across all regions of California, optimized CH<sub>4</sub> emissions are only marginally consistent between CALGEM‐ and EDGAR42‐based inversions (48.35 ± 6.47 versus 64.97 ± 11.85 Tg CO<sub>2</sub>eq), because emissions from coastal urban regions (where landfill and natural gas emissions are much higher in EDGAR than CALGEM) are not strongly constrained by the measurements. Combining our results with those from a recent study of the South Coast Air Basin narrows the range of estimates to 43–57 Tg CO<sub>2</sub>eq yr<sup>−1</sup> (1.3–1.8 times higher than the current state inventory). These results suggest that the combination of rural and urban measurements will be necessary to verify future changes in California's total CH<sub>4</sub> emissions.</p> </abstract>