Mapping methane super-emitters in China and United States with GF-5 02 hyperspectral imaging spectrometer
Rapid identification of anomalous methane sources in the fossil fuel industry would enable action to reduce greenhouse gas emissions.Spaceborne hyperspectral imaging spectrometers have recently been shown to be instrumental for this mission.In this study,we utilize the rapid development of spaceborne imaging spectroscopy technology and data processing methods to perform a satellite-based large-scale and high-resolution survey of methane super-emitters in China and the United States.Our dataset is acquired by the Advanced Hyperspectral Imager(AHSI)onboard domestic GF-5 02 satellite(i.e.,GF-5 02AHSI)and TROPOspheric Monitoring Instrument(TROPOMI)onboard European Space Agency's Sentinel-5 Precursor satellite(Sentinel-5P).Our core objective is to identify,quantify,and assess uncertainty of methane point emissions from coal mines and oil/gas facilities in China and the United States,with the overarching motivation of assisting future emission reduction efforts.Major steps include the following:(1)We retrieve methane concentration enhancements(i.e.,increments above background levels in the amount of methane present in the atmospheric column,△XCH4)using the optimized matched-filter algorithm applied to GF-5 02AHSI spectra in the 2300 nm shortwave infrared spectral region.(2)Emission plumes in the △XCH4 maps are detected based on a semi-automatic method.(3)We estimate the source rate(Q)for individual methane plume using the integrated mass enhancement(IME)method.(4)We estimate uncertainties in Q by propagating random errors in IME and U10 to a 1-σ precision error in Q.A 50％random error in wind speed is assumed for U10 data,which is consistent with the approximately 1.5 m/s error standard deviation in wind speed.(5)We further assess the magnitude of our estimated plume-level emission rates through a simulation-based study with the weather research forecast model coupled with large eddy simulation.Major findings include the following:(1)GF-5 02AHSI has detected four significant methane point source leak emissions in methane hotspot regions of China and the United States,with the emission rates greater than 0.5 tons per hour.A super-emitter is detected in the Permian Basin,and the emission amount is 11.7±4.4 tons per hour.(2)The estimation of methane point source emission flux rate is affected by the background meteorological field,and the uncertainty of wind speed at the point source has the largest contribution.Findings demonstrate the potential of GF-5 02AHSI in remote sensing identification and estimation of global methane point emissions,which can provide important data support for future methane leak detection in the global energy industry.
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