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

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.

[1]  A. VanderZaag,et al.  Effects of winter storage conditions and subsequent agitation on gaseous emissions from liquid dairy manure , 2010 .

[2]  Tarek Abichou,et al.  Methane emissions from 20 landfills across the United States using vertical radial plume mapping , 2012, Journal of the Air & Waste Management Association.

[3]  Seongeun Jeong,et al.  On the sources of methane to the Los Angeles atmosphere. , 2012, Environmental science & technology.

[4]  M. V. van Loosdrecht,et al.  Methane emission during municipal wastewater treatment. , 2012, Water research.

[5]  R. Desjardins,et al.  Towards an inventory of methane emissions from manure management that is responsive to changes on Canadian farms , 2013 .

[6]  Alex Hall,et al.  Local and synoptic mechanisms causing Southern California’s Santa Ana winds , 2010 .

[7]  K. Lassey,et al.  Seasonal variation in methane emission from dairy cows and breeding ewes grazing ryegrass/white clover pasture in New Zealand , 2002 .

[8]  R. Tibshirani,et al.  An introduction to the bootstrap , 1993 .

[9]  Lance E. Christensen,et al.  Isotopic measurements of atmospheric methane in Los Angeles, California, USA: Influence of "fugitive" fossil fuel emissions , 2012 .

[10]  Thomas K. Flesch,et al.  Measuring methane emissions from two dairy farms: seasonal and manure-management effects. , 2014 .

[11]  Shamil Maksyutov,et al.  A very high-resolution (1 km×1 km) global fossil fuel CO2 emission inventory derived using a point source database and satellite observations of nighttime lights , 2011 .

[12]  J. Bogner,et al.  From California dreaming to California data: Challenging historic models for landfill CH4 emissions , 2015 .

[13]  Kevin R. Gurney,et al.  A multiyear, global gridded fossil fuel CO2 emission data product: Evaluation and analysis of results , 2014 .

[14]  E. Kort,et al.  Top‐down estimate of methane emissions in California using a mesoscale inverse modeling technique: The South Coast Air Basin , 2015 .

[15]  Gregory J. Frost,et al.  Top-down estimate of surface flux in the Los Angeles Basin using a mesoscale inverse modeling technique: assessing anthropogenic emissions of CO, NOx and CO2 and their impacts , 2012 .

[16]  R. Tibshirani,et al.  The bootstrap estimate of standard error , 1993 .

[17]  Dejian Fu,et al.  Near-infrared remote sensing of Los Angeles trace gas distributions from a mountaintop site , 2013 .

[18]  M C M van Loosdrecht,et al.  Methane and nitrous oxide emissions from municipal wastewater treatment - results from a long-term study. , 2013, Water science and technology : a journal of the International Association on Water Pollution Research.

[19]  John R. Worden,et al.  Spatially resolving methane emissions in California: constraints from the CalNex aircraft campaign and from present (GOSAT, TES) and future (TROPOMI, geostationary) satellite observations , 2014 .

[20]  Paul O. Wennberg,et al.  Emissions of greenhouse gases from a North American megacity: GREENHOUSE GAS EMISSIONS IN LA , 2009 .

[21]  Mark S. Zahniser,et al.  Methane emissions from natural gas infrastructure and use in the urban region of Boston, Massachusetts , 2015, Proceedings of the National Academy of Sciences.

[22]  Alex Hall,et al.  Local Regimes of Atmospheric Variability: A Case Study of Southern California , 2006 .

[23]  R. Desjardins,et al.  Methane emissions from above ground open manure slurry tanks , 1998 .

[24]  Ira Leifer,et al.  Airborne visualization and quantification of discrete methane sources in the environment , 2014 .

[25]  Gregory J. Frost,et al.  Quantifying sources of methane using light alkanes in the Los Angeles basin, California , 2013 .

[26]  A. VanderZaag,et al.  Gas Emissions from Straw Covered Liquid Dairy Manure during Summer Storage and Autumn Agitation , 2009 .

[27]  J. Randerson,et al.  Spatial patterns and source attribution of urban methane in the Los Angeles Basin , 2016 .

[28]  E. Kort,et al.  Mapping CH 4 : CO 2 ratios in Los Angeles with CLARS-FTS from Mount Wilson, California , 2014 .

[29]  M. Fischer,et al.  A multitower measurement network estimate of California's methane emissions , 2013 .

[30]  Seong Suk Park,et al.  Methane emissions inventory verification in southern California , 2010 .

[31]  J. Bogner,et al.  A process‐based inventory model for landfill CH4 emissions inclusive of seasonal soil microclimate and CH4 oxidation , 2011 .