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Published September 15, 2018 | public
Journal Article

Evaluating the effects of surface properties on methane retrievals using a synthetic airborne visible/infrared imaging spectrometer next generation (AVIRIS-NG) image

Abstract

Atmospheric methane has been increasing since the beginning of the industrial era due to anthropogenic emissions. Methane has many sources, both natural and anthropogenic, and there continues to be considerable uncertainty regarding the contribution of each source to the total methane budget. Thus, remote sensing techniques for monitoring and measuring methane emissions are of increasing interest. Recently, the Airborne Visible-Infrared Imaging Spectrometer - Next Generation (AVIRIS-NG) has proven to be a valuable instrument for quantitative mapping of methane plumes. Despite this success, uncertainties remain regarding the sensitivity of the retrieval algorithms, including the influence of albedo and the impact of surfaces that may cause spurious signals. To explore these sensitivities, we applied the Iterative Maximum a Posterior Differential Optical Absorption Spectroscopy (IMAP-DOAS) methane retrieval algorithm to synthetic reflected radiances with variable methane concentrations, albedo, surface cover, and aerosols. This allowed for characterizing retrieval performance, including potential sensitivity to variable surfaces, low albedo surfaces, and surfaces known to cause spurious signals. We found that dark surfaces (below 0.10 μWcm^(−2)nm^(−1)sr^(−1) at 2139 nm), such as water and green vegetation, and materials with absorption features in the 2200–2400 nm range caused higher errors in retrieval results. We also found that aerosols have little influence on retrievals in the SWIR. Results from the synthetic scene are consistent with those observed in IMAP-DOAS retrievals for real AVIRIS-NG scenes containing methane plumes from a waste dairy lagoon and coal mine ventilation shafts. Understanding the effect of surface properties on methane retrievals is important given the increased use of AVIRIS-NG to map gas plumes from a diversity of sources over variable landscapes.

Additional Information

© 2018 Published by Elsevier Inc. Received 24 December 2017, Revised 4 June 2018, Accepted 14 June 2018, Available online 27 June 2018. The authors thank NASA HQ and Jack Kaye for funding the AVIRIS-NG flights used in this study. We would also like to thank Riley Duren for contributing to project planning and acknowledge the contributions of Robert Green, David Thompson, and the rest of the AVIRIS-NG instrument and flight teams. Portions of this research were supported the Chevron Energy Technology Company. This work was undertaken in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA as well as at the University of California, Santa Barbara. The AVIRIS-NG data used in this study are available upon request at http://avirisng.jpl.nasa.gov/ or http://aviris.jpl.nasa.gov/.

Additional details

Created:
August 23, 2023
Modified:
October 18, 2023