Mueller, K.
(2019),
Spatio-temporally resolved methane fluxes from the Los Angeles Megacity, Journal of Geophysical Research-Atmospheres, [online], https://doi.org/10.1029/2018JD030062
(Accessed May 9, 2025)
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Spatio-temporally resolved methane fluxes from the Los Angeles Megacity
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We combine sustained observations from a network of atmospheric monitoring stations with inverse modeling to uniquely obtain (3 km, 4 day) spatio-temporal estimates of methane emissions from the Los Angeles Megacity and the broader South Coast Air Basin (SoCAB) for 2015-2016. Our inversions use customized and validated high fidelity meteorological output from Weather Research Forecasting and Stochastic Time Inverted Lagrangian model for SoCAB and innovatively employ a model resolution matrix based metric to disentangle the spatio-temporal information content of observations as manifested through estimated fluxes. We partially track and constrain fluxes from the Aliso Canyon natural gas leak and detect closure of the Puente Hills landfill, with no prior information. Our annually aggregated fluxes and its uncertainty excluding the Aliso Canyon leak period lie within the uncertainty bounds of the fluxes reported by the previous studies. Spatially, major sources of CH4 emissions in the basin were correlated with CH4 emitting infrastructure. Temporally, our findings show large seasonal variations in CH4 fluxes with significantly higher fluxes in winter in comparison to summer months, which was consistent with natural gas demand and anti-correlated with air-temperature. Overall, this is the first study that utilizes inversions to detect both enhancement (Aliso Canyon Leak) and reduction (Puente Hills) in CH4 fluxes due to unintended events and policy decisions and thereby demonstrates the utility of inverse modeling for identifying variations in fluxes at fine spatio-temporal resolution.Citation
Journal of Geophysical Research-Atmospheres
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Created May 13, 2019, Updated March 14, 2025