Coordinated satellite, aircraft, and ground-based observations of a large transient methane release

Signficance: Methane is a potent greenhouse gas, and emissions from oil and gas infrastructure are a major mitigation target. Satellites are increasingly used to detect and quantify these emissions, but evaluating their estimates of releases remains challenging. In this study, we analyze a US gas pipeline blowdown in New Mexico using coordinated observations from nine satellites, an aircraft, and a truck-based mobile laboratory. Our experiment provides a rare opportunity to evaluate the accuracy of satellite-based observations of large, short-lived methane point sources. We show that geostationary satellites can continuously track and quantify such releases, with emission estimates consistent with other platforms and expectations from pipeline pressure and volume. Our results build confidence in satellite observations to monitor extreme methane releases worldwide.

Abstract: We present the results of a Very Large Methane Release (VLMR) experiment evaluating methane retrievals from the Geostationary Operational Environmental Satellites (GOES) Advanced Baseline Imagers (ABIs) and multiple low-Earth-orbit satellite instruments with high point-source detection thresholds. The experiment coordinated observations of a US gas pipeline blowdown with nine satellites, an aircraft, and a truck-based mobile laboratory. We used the GOES-16, -18, and -19 ABIs with revisits every 10 min to 7 s to quantify release magnitude and associated uncertainty. 

Best methane retrieval precision of 7% was achieved in the 30-s mesoscale scan modes averaged to 5 min, yielding an estimated methane plume detection threshold of 15 to 30 t h−1 per m s−1 of wind. GOES detected total emissions of 370 ± 30 t over 42 to 63 min from two release points. Source rate and mass estimates are broadly consistent across measurement platforms, but the total detected release mass is ~25% lower than that reported by the operator based on pipeline volume and pressure. This discrepancy may reflect late-stage emissions below satellite detection thresholds and indicates a potential low bias in satellite estimates of total emissions from large transient releases. 

Coordinated field experiments such as VLMR can complement existing controlled-release satellite evaluation programs by providing a framework to validate observations of very large methane point sources.