Combining TROPOMI with high-resolution satellites to detect, attribute, and monitor large methane emission events.

Anthropogenic methane emissions play an important role in exacerbating climate change, and thus there is a need for accurate and timely monitoring and mitigation of these emissions. With daily global coverage, TROPOMI, onboard Sentinel-5P, maps methane concentrations at 5.5 x 7 km2 resolution and can detect methane super-emitters (>~8 t hr-1) globally [1,2]. Here, we show how we detect, attribute, and quantify methane emissions from super-emitters using TROPOMI in combination with information from high-resolution satellite instruments to support the UNEP IMEO Methane Alert Response System (MARS). To determine optimal targets for high-resolution hyperspectral observations (e.g. PRISMA, EnMAP), we combine longer term TROPOMI data over persistent emitters. When emissions are transient, we combine TROPOMI with data from non-targeted high-resolution band imagers (also known as multispectral sensors) such as Sentinel-2 and Sentinel-3 to trace emissions to facility-level emission sources, in particular oil and gas infrastructure [3]. We illustrate how the combination of satellites with different overpass times and different spatial resolutions gives a comprehensive picture of these emissions. To evaluate the detections, we compare methane enhancements retrieved from band imagers with values from TROPOMI. Even when overpass times do not match, we achieve this by using transient emissions that result in methane plumes with a constant total mass, once detached from the source. Finally, we show how combining information from multiple satellites enables critical evaluation of the winds taken from global reanalysis products that underlie almost all high-resolution emission quantifications based on mass-balance methods. References[1] Maasakkers JD, Varon DJ, Elfarsdóttir A, McKeever J, Jervis D, Mahapatra G, et al. Using satellites to uncover large methane emissions from landfills. Sci Adv 2022;8:eabn9683. https://doi.org/10.1126/sciadv.abn9683.[2] Irakulis-Loitxate I, Guanter L, Maasakkers JD, Zavala-Araiza D, Aben I. Satellites Detect Abatable Super-Emissions in One of the World’s Largest Methane Hotspot Regions. Environ Sci Technol 2022;56:2143–52. https://doi.org/10.1021/acs.est.1c04873.[3] Pandey, Sudhanshu, et al. "Daily detection and quantification of methane leaks using Sentinel-3: a tiered satellite observation approach with Sentinel-2 and Sentinel-5p." Remote Sensing of Environment 296 (2023): 113716. https://doi.org/10.1016/j.rse.2023.1137

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