Challenges in Methane Column Retrievals from AVIRIS-NG Imagery Over Spectrally Cluttered Surfaces: A Sensitivity Analysis

Authors

Minwei Zhang, University of South Florida
Ira Leifer, Bubbleology Research International
Chuanmin Hu, University of South FloridaFollow

Document Type

Article

Publication Date

2017

Keywords

methane, AVIRIS-NG, albedo sensitivity, spectral clutter, spatial heterogeneity, GOSAT, remote sensing

Digital Object Identifier (DOI)

https://doi.org/10.3390/rs9080835

Abstract

A comparison between efforts to detect methane anomalies by a simple band ratio approach from the Airborne Visual Infrared Imaging Spectrometer-Classic (AVIRIS-C) data for the Kern Front oil field, Central California, and the Coal Oil Point marine hydrocarbon seep field, offshore southern California, was conducted. The detection succeeded for the marine source and failed for the terrestrial source, despite these sources being of comparable strength. Scene differences were investigated in higher spectral and spatial resolution collected by the AVIRIS-C successor instrument, AVIRIS Next Generation (AVIRIS-NG), by a sensitivity study. Sensitivity to factors including water vapor, aerosol, planetary boundary layer (PBL) structure, illumination and viewing angle, and surface albedo clutter were explored. The study used the residual radiance method, with sensitivity derived from MODTRAN (MODerate resolution atmospheric correction TRANsmission) simulations of column methane (XCH₄). Simulations used the spectral specifications and geometries of AVIRIS-NG and were based on a uniform or an in situ vertical CH₄ profile, which was measured concurrent with the AVIRIS-NG data. Small but significant sensitivity was found for PBL structure and water vapor; however, highly non-linear, extremely strong sensitivity was found for surface albedo error. For example, a 10% decrease in the surface albedo corresponded to a 300% XCH₄ increase over background XCH₄ to compensate for the total signal, less so for stronger plumes. This strong non-linear sensitivity resulted from the high percentage of surface-reflected radiance in the airborne at-sensor total radiance. Coarse spectral resolution and feedback from interferents like water vapor underlay this sensitivity. Imaging spectrometry like AVIRIS and the Hyperspectral InfraRed Imager (HyspIRI) candidate satellite mission, have the advantages of contextual spatial information and greater at-sensor total radiance. However, they also face challenges due to their relatively broad spectral resolution compared to trace gas specific orbital sensors, e.g., the Greenhouse gases Observing SATellite (GOSAT), which is especially applicable to trace gas retrievals over scenes with high spectral albedo variability. Results of the sensitivity analysis are applicable for the residual radiance method and CH₄ profiles used in the analysis, but they illustrate potential significant challenges in CH₄ retrievals using other approaches. View Full-Text

Rights Information

This work is licensed under a Creative Commons Attribution 4.0 License.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Remote Sensing, v. 9, issue 8, art. 835

Scholar Commons Citation

Zhang, Minwei; Leifer, Ira; and Hu, Chuanmin, "Challenges in Methane Column Retrievals from AVIRIS-NG Imagery Over Spectrally Cluttered Surfaces: A Sensitivity Analysis" (2017). Marine Science Faculty Publications. 1881.
https://digitalcommons.usf.edu/msc_facpub/1881