Characterization of methane plumes during the Aliso Canyon natural gas leak: a remote sensing perspective

Abstract Starting on October 23, 2015, wellhead failure at the Aliso Canyon gas storage facility led to a massive blowout near a populated area in Los Angeles County. Aircraft mass balance flights during the event estimated the methane release effectively doubled the total emissions from the Los Angeles basin by the time the leak was capped in February 2016. The plume extent and its spatiotemporal evolution, however, is less well-characterized. Here, we examine the total methane released during the event and the spatial extent of methane plumes using satellite and aircraft remote sensing observations available during the event. In particular, with the inclusion of Landsat-8 and Sentinel-2 satellite observations, we have access to multiple observations earlier during the event history than previously reported. In conjunction with the Hyperion satellite and Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instruments that were available later in the event, we quantify total methane released with more independent and publicly available measurements than previously reported. We find the atmospheric column was enhanced in methane as much as 14 km downwind of the site into February 2016. We compare AVIRIS column enhancements to nearby air quality monitoring stations and find that elevated surface concentrations from stations correlate with plume morphology from remote sensing imagery. Though further research is required to relate atmospheric column enhancement to surface exposure, we show remote sensing to be a powerful tool for estimating emissions and the potential population exposure zone from the Aliso Canyon event.