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