Assessing the capability of different satellite observing configurations to resolve the distribution of methane emissions at kilometer scales

Anthropogenic methane emissions originate from a large number of fine-scale and of1 ten transient point sources. Satellite observations of atmospheric methane columns are an attractive 2 approach for monitoring these emissions but have limitations from instrument precision, pixel reso3 lution, and measurement frequency. Dense observations will soon be available in both low Earth and 4 geostationary orbits, but the extent to which they can provide fine-scale information on methane 5 sources has yet to be explored. Here we present an observation system simulation experiment 6 (OSSE) to assess the capabilities of different satellite observing system configurations. We conduct a 7 1-week WRF-STILT simulation to generate methane column footprints at 1.3×1.3 km spatial reso8 lution and hourly temporal resolution over a 290×235 km domain in the Barnett Shale in Northeast 9 Texas, a major oil/gas field with a large number of point sources. We sub-sample these footprints 10 to match the observing characteristics of the recently launched TROPOMI instrument (7×7 km 11 pixels, 11 ppb precision, daily frequency), the planned GeoCARB instrument (2.7×3.0 km pixels, 12 4 ppb precision, nominal twice-daily frequency), and other proposed observing configurations. The 13 information content of the various observing systems is evaluated using the Fisher information ma14 trix and its eigenvalues. We find that a week of TROPOMI observations should effectively provide 15 regional (∼100 km) information on temporally invariant emissions but is very limited at finer scales. 16 GeoCARB should provide 4-37% of the total information available for temporally invariant emis17 sions in the Barnett Shale (∼100 pieces of information). Improvements to the instrument precision 18 yield greater increases in information content, compared to improved sampling frequency. A preci19 sion better than 6 ppb is an important threshold for achieving fine resolution of emissions. Transient 20