Articles | Volume 16, issue 20
Atmos. Chem. Phys., 16, 13121–13130, 2016
Atmos. Chem. Phys., 16, 13121–13130, 2016

Research article 26 Oct 2016

Research article | 26 Oct 2016

Monthly trends of methane emissions in Los Angeles from 2011 to 2015 inferred by CLARS-FTS observations

Clare K. Wong1,2,a, Thomas J. Pongetti1, Tom Oda3,4, Preeti Rao1, Kevin R. Gurney5, Sally Newman2, Riley M. Duren1, Charles E. Miller1, Yuk L. Yung2, and Stanley P. Sander1 Clare K. Wong et al.
  • 1NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
  • 2Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
  • 3Goddard Earth Sciences Technology and Research, Universities Space Research Association, Columbia, Maryland, USA
  • 4Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 5School of Life Sciences, Arizona State University, Tempe, Arizona, USA
  • acurrently at: California State University, Northridge, California, USA

Abstract. This paper presents an analysis of methane emissions from the Los Angeles Basin at monthly timescales across a 4-year time period – from September 2011 to August 2015. Using observations acquired by a ground-based near-infrared remote sensing instrument on Mount Wilson, California, combined with atmospheric CH4–CO2 tracer–tracer correlations, we observed −18 to +22 % monthly variability in CH4 : CO2 from the annual mean in the Los Angeles Basin. Top-down estimates of methane emissions for the basin also exhibit significant monthly variability (−19 to +31 % from annual mean and a maximum month-to-month change of 47 %). During this period, methane emissions consistently peaked in the late summer/early fall and winter. The estimated annual methane emissions did not show a statistically significant trend over the 2011 to 2015 time period.

Short summary
Methane is the second most important greenhouse gas and a target of new emissions regulations in the United States. Despite its importance, its emissions are poorly understood. In this study, we used a remote sensing instrument located on Mount Wilson to estimate the monthly and annual methane emissions from Los Angeles. Derived methane emissions from Los Angeles showed consistent peaks in late summer/early fall and winter during the study period from 2011 to 2015.
Final-revised paper