Publication Date:
2018-02-19
Description:
Anthropogenic methane emissions originate from a large number of fine-scale and often transient point sources. Satellite observations of atmospheric methane columns are an attractive approach for monitoring these emissions but have limitations from instrument precision, pixel resolution, and measurement frequency. Dense observations will soon be available in both low Earth and geostationary orbits, but the extent to which they can provide fine-scale information on methane sources has yet to be explored. Here we present an observation system simulation experiment (OSSE) to assess the capabilities of different satellite observing system configurations. We conduct a 1-week WRF-STILT simulation to generate methane column footprints at 1.3×1.3 km2 spatial resolution and hourly temporal resolution over a 290×235 km2 domain in the Barnett Shale in Northeast Texas, a major oil/gas field with a large number of point sources. We sub-sample these footprints to match the observing characteristics of the recently launched TROPOMI instrument (7×7 km2 pixels, 11 ppb precision, daily frequency), the planned GeoCARB instrument (2.7×3.0 km2 pixels, 4 ppb precision, nominal twice-daily frequency), and other proposed observing configurations. The information content of the various observing systems is evaluated using the Fisher information matrix and its eigenvalues. We find that a week of TROPOMI observations should effectively provide regional (~100 km) information on temporally invariant emissions but is very limited at finer scales. GeoCARB should provide 4–37 % of the total information available for temporally invariant emissions in the Barnett Shale (~100 pieces of information). Improvements to the instrument precision yield greater increases in information content, compared to improved sampling frequency. A precision better than 6 ppb is an important threshold for achieving fine resolution of emissions. Transient emissions would be missed with either TROPOMI or GeoCARB. An aspirational high-resolution geostationary instrument with 1.3×1.3 km2 pixel resolution, hourly return time, and 1 ppb precision would effectively constrain the temporally invariant emissions in the Barnett Shale at the kilometer scale and provide some information on transient sources.
Electronic ISSN:
1680-7375
Topics:
Geosciences
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