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| Titel |
MAMAP – a new spectrometer system for column-averaged methane and carbon dioxide observations from aircraft: instrument description and performance analysis |
| VerfasserIn |
K. Gerilowski, A. Tretner, T. Krings, M. Buchwitz, P. P. Bertagnolio, F. Belemezov, J. Erzinger, J. P. Burrows, H. Bovensmann |
| 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 ; 4, no. 2 ; Nr. 4, no. 2 (2011-02-10), S.215-243 |
| Datensatznummer |
250001672
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| Publikation (Nr.) |
 copernicus.org/amt-4-215-2011.pdf |
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| Zusammenfassung |
| Carbon dioxide (CO2) and Methane (CH4) are the two most important
anthropogenic greenhouse gases. CH4 is furthermore one of the most
potent present and future contributors to global warming because of its large
global warming potential (GWP). Our knowledge of CH4 and CO2 source
strengths is based primarily on bottom-up scaling of sparse in-situ local
point measurements of emissions and up-scaling of emission factor estimates
or top-down modeling incorporating data from surface networks and more
recently also by incorporating data from low spatial resolution satellite
observations for CH4. There is a need to measure and retrieve the dry
columns of CO2 and CH4 having high spatial resolution and spatial
coverage. In order to fill this gap a new passive airborne 2-channel grating
spectrometer instrument for remote sensing of small scale and mesoscale
column-averaged CH4 and CO2 observations has been developed. This
Methane Airborne MAPper (MAMAP) instrument measures reflected and scattered
solar radiation in the short wave infrared (SWIR) and near-infrared (NIR)
parts of the electro-magnetic spectrum at moderate spectral resolution. The
SWIR channel yields measurements of atmospheric absorption bands of CH4
and CO2 in the spectral range between 1.59 and 1.69 μm at a
spectral resolution of 0.82 nm. The NIR channel around 0.76 μm
measures the atmospheric O2-A-band absorption with a resolution of
0.46 nm. MAMAP has been designed for flexible operation aboard a variety of
airborne platforms. The instrument design and the performance of the SWIR
channel, together with some results from on-ground and in-flight engineering
tests are presented. The SWIR channel performance has been analyzed using
a retrieval algorithm applied to the nadir measured spectra. Dry air
column-averaged mole fractions are obtained from SWIR data only by dividing
the retrieved CH4 columns by the simultaneously retrieved CO2
columns for dry air column CH4 (XCH4) and vice versa for dry air
column CO2 (XCO2). The signal-to-noise ratio (SNR) of the SWIR
channel is approximately 1000 for integration times (tint) in the
range of 0.6–0.8 s for scenes with surface spectral reflectances
(SSR)/albedo of around 0.18. At these integration times the ground scene size
is about 23 × 33 m2 for an aircraft altitude of 1 km and a
ground speed of 200 km/h. For these scenes the actual XCH4 or
XCO2 dry air column retrieval precisions are typically about 1%
(1 σ). Elevated levels of CH4 have been retrieved above a
CH4 emitting landfill. Similarly the plume of CO2 from coal-fired
power plants can be well detected and tracked. The measurements by the MAMAP
sensor could enable estimates of anthropogenic, biogenic and geological
emissions of localized intense CH4 and CO2 sources such as
anthropogenic fugitive CH4 emissions from oil and gas industry, coal
mining, disposal of organic waste, CO2 emissions from coal-fired power
plants, steel production or geologic CH4 and CO2 emissions from
seepage and volcanoes. Appropriate analysis of the measurements of MAMAP
potentially also yields natural CH4 emissions from less intense but
extensive sources such as wetlands. |
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