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Title: Estimating methane emissions in California's urban and rural regions using multitower observations

Here, we present an analysis of methane (CH 4) emissions using atmospheric observations from 36 thirteen sites in California during June 2013 – May 2014. A hierarchical Bayesian inversion 37 method is used to estimate CH 4 emissions for spatial regions (0.3° pixels for major regions) by 38 comparing measured CH 4 mixing ratios with transport model (WRF-STILT) predictions based 39 on seasonally varying California-specific CH 4 prior emission models. The transport model is 40 assessed using a combination of meteorological and carbon monoxide (CO) measurements 41 coupled with the gridded California Air Resources Board (CARB) carbon monoxide (CO) 42 emission inventory. Hierarchical Bayesian inversion suggests that state annual anthropogenic 43 CH 4 emissions are 2.42 ± 0.49 Tg CH 4/yr (at 95% confidence, including transport bias 44 uncertainty), higher (1.2 - 1.8 times) than the CARB current inventory (1.64 Tg CH 4/yr in 2013). 45 We note that the estimated CH 4 emissions drop to 1.0 - 1.6 times the CARB inventory if we 46 correct for the 10% median CH 4 emissions assuming the bias in CO analysis is applicable to 47 CH 4. The CH 4 emissions from the Central Valley and urban regions (San Francisco Baymore » and 48 South Coast Air Basins) account for ~58% and 26% of the total posterior emissions, 49 respectively. This study suggests that the livestock sector is likely the major contributor to the 50 state total CH 4 emissions, in agreement with CARB’s inventory. Attribution to source sectors for 51 sub-regions of California using additional trace gas species would further improve the 52 quantification of California’s CH 4 emissions and mitigation efforts towards the California Global 53 Warming Solutions Act of 2006 (AB-32).« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1] ;  [1] ;  [6] ;  [7] ;  [7] ;  [8] ;  [3] ;  [3] ;  [9] ;  [9] ;  [8] ;  [8] ;  [7] ;  [7] ;  [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  3. Univ. of California, Riverside, CA (United States)
  4. NOAA, Boulder, CO (United States)
  5. NOAA, Boulder, CO (United States); Univ. of Colorado, Boulder, CO (United States)
  6. Imperial College London, London (United Kingdom)
  7. Univ. of California, San Diego, La Jolla, CA (United States)
  8. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
  9. Earth Networks, Germantown, MD (United States)
Publication Date:
Report Number(s):
LBNL-1005846
Journal ID: ISSN 2169-897X; ir:1005846
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research: Atmospheres
Additional Journal Information:
Journal Volume: 121; Journal Issue: 21; Journal ID: ISSN 2169-897X
Publisher:
American Geophysical Union
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
Energy Analysis & Environmental Impacts; USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1342759