Mapping Methane Point Sources in an Urban Airshed Using Imaging Spectroscopy

Abstract:

Imaging spectroscopy has become a powerful tool for mapping point source methane emissions, and is one tier of the CMS Multi-tiered Carbon Monitoring System project. Recent studies using imaging spectroscopy have verified that emissions have a “heavy tail” – a small percentage of facilities are responsible for a large percentage of total emissions. To determine whether a similar heavy-tailed distribution occurs within an urban airshed, the Global Airborne Observatory (GAO) was flown over the extent of the Salt Lake Valley in summer 2020. The area flown (~1000 km²) is home to over a million people, and includes a landfill and multiple industrial facilities, refineries, and waste water treatment plants. Matched filter retrieval of methane enhancements from shortwave infrared spectra was used to map point sources and estimate point source emission rates. Plumes and emission rates were qualitatively compared to data from an extensive network of ground observations operating during GAO flights. Our work to identify urban anthropogenic methane sources will further refinement of methane retrieval algorithms over diverse backgrounds, play a role in emissions mitigation, and support evaluation of and potential improvements in local greenhouse gas inventories.