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Methane retrievals from airborne HySpex observations in the shortwave infrared

Hochstaffl, Philipp and Schreier, Franz and Köhler, Claas Henning and Baumgartner, Andreas and Cerra, Daniele (2023) Methane retrievals from airborne HySpex observations in the shortwave infrared. Atmospheric Measurement Techniques (AMT), 16 (18), pp. 4195-4214. Copernicus Publications. doi: 10.5194/amt-16-4195-2023. ISSN 1867-1381.

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Official URL: https://dx.doi.org/10.5194/amt-16-4195-2023


Monitoring anthropogenic emissions is a crucial aspect in understanding the methane budget. Moreover, a reduction of methane emissions could help to mitigate global warming on a short timescale. This study compares various retrieval schemes for estimating localized methane enhancements around ventilation shafts in the Upper Silesian Coal Basin in Poland using nadir observations in the shortwave infrared acquired from the airborne imaging spectrometer HySpex. Linear and nonlinear solvers are examined and compared, with special emphasis put on strategies that tackle degeneracies between the surface reflectivity and broad-band molecular absorption features --- a challenge arising from the instrument's low spectral resolution. Results reveal that the generalized nonlinear least squares fit, employed within the Beer InfraRed Retrieval Algorithm (BIRRA), can measure enhanced methane levels with notable accuracy and precision. This is accomplished by allowing the scene's background covariance structure to account for surface reflectivity statistics. Linear estimators such as matched filter (MF) and singular value decomposition (SVD) are able to detect and, under favorable conditions, quantify enhanced levels of methane quickly. Using k-means clustering as a preprocessing step can further enhance the performance of the two linear solvers. The linearized BIRRA fit (LLS) underestimates methane but agrees on the enhancement pattern. The non-quantitative spectral signature detection (SSD) method does not require any forward modeling and can be useful in the detection of relevant scenes. In conclusion, the BIRRA code, originally designed for the retrieval of atmospheric constituents from spaceborne high-resolution spectra, turned out to be applicable to hyperspectral airborne imaging data for the quantification of methane plumes from point-like sources. Moreover, it is able to outperform well-established linear schemes such as the MF or SVD at the expense of high(er) computing time.

Item URL in elib:https://elib.dlr.de/197418/
Document Type:Article
Title:Methane retrievals from airborne HySpex observations in the shortwave infrared
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Hochstaffl, PhilippUNSPECIFIEDhttps://orcid.org/0000-0001-9537-3050UNSPECIFIED
Schreier, FranzUNSPECIFIEDhttps://orcid.org/0000-0001-7196-6599UNSPECIFIED
Köhler, Claas HenningUNSPECIFIEDhttps://orcid.org/0000-0003-0127-935XUNSPECIFIED
Baumgartner, AndreasUNSPECIFIEDhttps://orcid.org/0000-0002-8495-5407143033387
Cerra, DanieleUNSPECIFIEDhttps://orcid.org/0000-0003-2984-8315UNSPECIFIED
Date:September 2023
Journal or Publication Title:Atmospheric Measurement Techniques (AMT)
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:Yes
Page Range:pp. 4195-4214
Publisher:Copernicus Publications
Keywords:Anthropogenic emissions, hyperspectral imaging, radiative transfer, retrieval methods, HySpex
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Earth Observation
DLR - Research theme (Project):R - Spectroscopic methods of the atmosphere
Location: Oberpfaffenhofen
Institutes and Institutions:Remote Sensing Technology Institute > Atmospheric Processors
Remote Sensing Technology Institute > Experimental Methods
Remote Sensing Technology Institute > Photogrammetry and Image Analysis
Deposited By: Hochstaffl, Dr. Philipp
Deposited On:26 Sep 2023 14:03
Last Modified:26 Oct 2023 15:22

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