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

摘要

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 CHsub4/sub–COsub2/sub tracer–tracer correlations, we observed ?18 to +22?% monthly variability in CHsub4/sub?:?COsub2/sub 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.