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Title: Analyzing source apportioned methane in northern California during Discover-AQ-CA using airborne measurements and model simulations

This study analyzes source apportioned methane (CH 4) emissions and atmospheric mixing ratios in northern California during the Discover-AQ-CA field campaign using airborne measurement data and model simulations. Source apportioned CH 4 emissions from the Emissions Database for Global Atmospheric Research (EDGAR) version 4.2 were applied in the 3-D chemical transport model GEOS-Chem and analyzed using airborne measurements taken as part of the Alpha Jet Atmospheric eXperiment over the San Francisco Bay Area (SFBA) and northern San Joaquin Valley (SJV). During the time period of the Discover-AQ-CA field campaign EDGAR inventory CH 4 emissions were ~5.30 Gg day –1 (Gg = 1.0 × 10 9 g) (equating to ~1.90 × 10 3 Gg yr –1) for all of California. According to EDGAR, the SFBA and northern SJV region contributes ~30% of total CH 4 emissions from California. Source apportionment analysis during this study shows that CH 4 mixing ratios over this area of northern California are largely influenced by global emissions from wetlands and local/global emissions from gas and oil production and distribution, waste treatment processes, and livestock management. Model simulations, using EDGAR emissions, suggest that the model under-estimates CH 4 mixing ratios in northern California (average normalized mean biasmore » (NMB) = –5.2% and linear regression slope = 0.20). The largest negative biases in the model were calculated on days when large amounts of CH 4 were measured over local emission sources and atmospheric CH 4 mixing ratios reached values >2.5 parts per million. Sensitivity emission studies conducted during this research suggest that local emissions of CH 4 from livestock management processes are likely the primary source of the negative model bias. These results indicate that a variety, and larger quantity, of measurement data needs to be obtained and additional research is necessary to better quantify source apportioned CH 4 emissions in California.« less
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  1. NASA Ames Research Center, Moffett Field, CA (United States). Earth Sciences Div.
  2. NASA Ames Research Center, Moffett Field, CA (United States). Earth Sciences Div.; Carnegie Institution for Science, Stanford, CA (United States). Dept. of Global Ecology.
  3. Harvard Univ., Cambridge, MA (United States). Dept. of Earth and Planetary Sciences.
  4. Lawrence Berkeley National Lab., Berkeley, CA (United States). Environmental Energy Technologies Div.
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Atmospheric Environment
Additional Journal Information:
Journal Volume: 99; Journal Issue: C; Journal ID: ISSN 1352-2310
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES; methane; source apportionment; emission inventory; livestock emissions
OSTI Identifier: