Publikationsdatum:
2015-06-14
Beschreibung:
Methane (CH 4 ) is the primary component of natural gas and has a larger global warming potential than CO 2 . Recent top-down studies based on observations showed CH 4 emissions in California's South Coast Air Basin (SoCAB) were greater than those expected from population-apportioned bottom-up state inventories. In this study, we quantify CH 4 emissions with an advanced mesoscale inverse modeling system at a resolution of 8 km × 8 km, using aircraft measurements in the SoCAB during the 2010 CalNex campaign to constrain the inversion. To simulate atmospheric transport, we use the FLEXPART-WRF Lagrangian particle dispersion model driven by three configurations of the Weather Research and Forecasting (WRF) mesoscale model. We determine surface fluxes of CH 4 using a Bayesian least squares method in a 4-dimensional inversion. Simulated CH 4 concentrations with the posterior emission inventory achieve much better correlations with the measurements (R 2 =0.7) than using the prior inventory (US EPA's National Emission Inventory 2005, R 2 =0.5). The emission estimates for CH 4 in the posterior, 46.3 ± 9.2 Mg CH 4 /hr, is consistent with published observation-based estimates. Changes in the spatial distribution of CH 4 emissions in the SoCAB between the prior and posterior inventories are discussed. Missing or underestimated emissions from dairies, the oil/gas system, and landfills in the SoCAB seem to explain the differences between the prior and posterior inventories. We estimate that dairies contributed 5.9 ± 1.7 Mg CH 4 /hr and the two sectors of oil and gas industry (production and downstream) and landfills together contributed 39.6 ± 8.1 Mg CH 4 /hr in the SoCAB.
Print ISSN:
0148-0227
Thema:
Geologie und Paläontologie
,
Physik
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