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Titel |
Retrieval techniques for airborne imaging of methane concentrations using high spatial and moderate spectral resolution: application to AVIRIS |
VerfasserIn |
A. K. Thorpe, C. Frankenberg, D. A. Roberts |
Medientyp |
Artikel
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Sprache |
Englisch
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ISSN |
1867-1381
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Digitales Dokument |
URL |
Erschienen |
In: Atmospheric Measurement Techniques ; 7, no. 2 ; Nr. 7, no. 2 (2014-02-10), S.491-506 |
Datensatznummer |
250115599
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Publikation (Nr.) |
copernicus.org/amt-7-491-2014.pdf |
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Zusammenfassung |
Two quantitative retrieval techniques were evaluated to estimate methane
(CH4) enhancement in concentrated plumes using high spatial and
moderate spectral resolution data from the Airborne Visible/Infrared Imaging
Spectrometer (AVIRIS). An iterative maximum a posteriori differential
optical absorption spectroscopy (IMAP-DOAS) algorithm performed well for an
ocean scene containing natural CH4 emissions from the Coal Oil Point
(COP) seep field near Santa Barbara, California. IMAP-DOAS retrieval
precision errors are expected to equal between 0.31 to 0.61 ppm CH4
over the lowest atmospheric layer (height up to 1.04 km), corresponding to
about a 30 to 60 ppm error for a 10 m thick plume. However, IMAP-DOAS
results for a terrestrial scene were adversely influenced by the underlying
land cover. A hybrid approach using singular value decomposition (SVD) was
particularly effective for terrestrial surfaces because it could better
account for spectral variability in surface reflectance. Using this
approach, a CH4 plume was observed extending 0.1 km downwind of two
hydrocarbon storage tanks at the Inglewood Oil Field in Los Angeles,
California (USA) with a maximum near surface enhancement of 8.45 ppm above
background. At COP, the distinct plume had a maximum enhancement of 2.85 ppm
CH4 above background, and extended more than 1 km downwind of known
seep locations. A sensitivity analysis also indicates CH4 sensitivity
should be more than doubled for the next generation AVIRIS sensor (AVIRISng)
due to improved spectral resolution and sampling. AVIRIS-like sensors offer
the potential to better constrain emissions on local and regional scales,
including sources of increasing concern like industrial point source
emissions and fugitive CH4 from the oil and gas industry. |
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