Abstract
Total column loadings of methane measured by satellites are increasingly used to estimate methane emission rates, using inversion calculations. Forward calculations of methane column loadings, based on detailed emission inventories at fine spatial resolution, coupled with fine spatial scale gridded chemical transport models, have the potential to inform approaches used in inversion calculations. As a case study of a forward calculation of methane column loadings, a site-level emission inventory for >104 oil and gas production and midstream sites was coupled with a gridded chemical transport model to estimate the variability in column loadings associated with routine emissions and large emission events from oil and gas facilities over a seven-month period. Data sets of gridded column concentrations at a one-hour temporal resolution and a 1.33 km horizontal spatial resolution have been created and archived. Ratios of the total column methane enhancements associated with emission events to the total column enhancements due to routine methane emissions were evaluated for various emission scenarios. The results indicate that in an oil and gas production region typical of the United States, a horizontal spatial resolution of ~1 km is needed for a 1000 kg/hr emission event to routinely produce a doubling of column methane loadings, compared to a baseline of enhancements in column loadings due to routine emissions. Enhancements ratios for column methane due to nearby emission events were generally insignificant. The enhancement ratio represents a relatively simple metric that could facilitate rapid and simple identification of emission events.
Supplementary materials
Title
Supporting Information of High spatial and temporal resolution simulations of methane column loadings due to routine emissions and emission events in oil and gas regions
Description
Summary statistics; time series of total column concentrations due to routine emissions and emission events; spatial distribution of total column concentrations; time series of enhancement ratios; and time series of ground concentration enhancements due to a 1000 kg/hr emission event
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Supplementary weblinks
Title
Description of Dataset and 1.33km and 4km Base CAMx modeling results
Description
Description of Datasets
Eagle Ford Shale CH4 and CO2 emissions (xslx)
CAMx gridded output files for 1.33km and 4km resolution modeling of routine emissions
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4km Event Column and Surface CAMx modeling
Description
Event Scenarios 4km:
low_100kg/1000kg: 100/1000 kg/hr emission event added with low routine emissions
med_100kg/1000kg: 100/1000 kg/hr emission event added with medium routine emissions
high_100kg/1000kg: 100/1000 kg/hr emission event added with high routine emissions
nearby_low/med/high: 100/1000kg/hr emission events added at nearby locations
For example, files under 'txs_4km/base/surface' represent hourly gridded surface CH4/CO2 concentration (ppmv) with a spatial resolution of 4km x 4km. Similarly, files under 'txs_13km/nearby_high/column' represent hourly gridded CH4 column concentration (mol/m2) with a spatial resolution of 4km x 4km under scenario 'nearby_high'.
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View Title
1.33km Event Column and Surface CAMx modeling
Description
Event Scenarios 1.33km
low_100kg/1000kg: 100/1000 kg/hr emission event added with low routine emissions
med_100kg/1000kg: 100/1000 kg/hr emission event added with medium routine emissions
high_100kg/1000kg: 100/1000 kg/hr emission event added with high routine emissions
nearby_low/med/high: 100/1000kg/hr emission events added at nearby locations
For example, files under 'txs_4km/base/surface' represent hourly gridded surface CH4/CO2 concentration (ppmv) with a spatial resolution of 4km x 4km. Similarly, files under 'txs_13km/nearby_high/column' represent hourly gridded CH4 column concentration (mol/m2) with a spatial resolution of 4km x 4km under scenario 'nearby_high'.
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