Quantifying methane emissions from the global scale down to point sources using satellite observations of atmospheric methane

Abstract

Abstract. We review the capability of current and scheduled satellite observations of atmospheric methane in the shortwave infrared (SWIR) to quantify methane emissions from the global scale down to point sources. We cover retrieval methods, precision and accuracy requirements, inverse and mass balance methods for inferring emissions, source detection thresholds, and observing system completeness. We classify satellite instruments as area flux mappers and point source imagers, with complementary attributes. Area flux mappers are high-precision (<1 %) instruments with 0.1–10 km pixel size designed to quantify total methane emissions on regional to global scales. Point source imagers are fine-pixel (<60 m) instruments designed to quantify individual point sources by imaging of the plumes. Current area flux mappers include GOSAT (2009–present), which provides a high-quality record for interpretation of long-term methane trends, and TROPOMI (2018–present), which provides global continuous daily mapping to quantify emissions on regional scales. These instruments already provide a powerful resource to quantify national methane emissions in support of the Paris Agreement. Current point source imagers include the GHGSat constellation and several hyperspectral and multispectral land imaging sensors (PRISMA, Sentinel-2, Landsat-8/9, WorldView-3), with detection thresholds in the 100–10 000 kg h−1 range that enable monitoring of large point sources. Future area flux mappers, including MethaneSAT, GOSAT-GW, Sentinel-5, GeoCarb, and CO2M, will increase the capability to quantify emissions at high resolution, and the MERLIN lidar will improve observation of the Arctic. The averaging times required by area flux mappers to quantify regional emissions depend on pixel size, retrieval precision, observation density, fraction of successful retrievals, and return times in a way that varies with the spatial resolution desired. A similar interplay applies to point source imagers between detection threshold, spatial coverage, and return time, defining an observing system completeness. Expanding constellations of point source imagers including GHGSat and Carbon Mapper over the coming years will greatly improve observing system completeness for point sources through dense spatial coverage and frequent return times.

Single-blind validation of space-based point-source methane emissions detection and quantification

“…Importantly, improved technology is on the way. At least eight constellations with point source imaging capability are in orbit or scheduled for launch by the end of 2023 12 . The constellation of satellites from Carbon Mapper has a designed detection limit of 0.05 -0.15 t/h, with revisit times of 1-7 days at full constellation deployment 33 .…”

“…The complementary MethaneSAT project from the Environmental Defense Fund will provide independent coverage using another advanced purpose-designed methane sensor, with both point source and wide-area methane flux estimation capabilities at somewhat larger spatial scales 34 . A total of eight area flux mapping satellites are scheduled for orbit by 2027 12 .…”

Monitoring greenhouse gases (GHGs) in China: status and perspective

“…Studies with satellite data have yielded anthropogenic CO 2 flux estimates at the scale of megacities or larger regions (Eldering et al, 2017) and recently have extended CO 2 emissions estimates at the scale of an individual facility, such as a single power plant (Nassar et al, 2017;Zheng et al, 2020a). Jacob et al (2022) have summarized the capability of current and scheduled satellite observations of atmospheric methane in the shortwave infrared (SWIR) to quantify CH 4 emissions from the global scale down to point sources, where XCH 4 precisions of various satellites were presented.…”

Automated detection and monitoring of methane super-emitters using satellite data

“…Frankenberg et al, 2016;Duren et al, 2019;Yu et al, 2022;Plant et al, 2022). While ground-based or airborne measurements are limited in spatial and temporal coverage, satellite observations have the potential for global monitoring of methane point-sources with frequent revisits (Jacob et al, 2016;Cusworth et al, 2019;Jacob et al, 2022). The TROPOspheric Monitoring Instrument (TROPOMI) (Veefkind et al, 2012) was launched in 2017 and observes atmospheric methane columnaveraged mixing ratios with a pixel size down to 7x5.5 km 2 and daily global coverage (Hu et al, 2018;Lorente et al, 2021), resulting in a point-source detection limit down to ∼5 t h -1 under favorable conditions (Jacob et al, 2016).…”