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| Titel |
Airborne Validation of Laser Remote Measurements of Atmospheric Carbon Dioxide |
| VerfasserIn |
Edward V. Browell, Jeremy Dobler, Susan A. Kooi, Yonghoon Choi, F. Wallace Harrison, Berrien Moore III, T. Scott Zaccheo |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034747
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| Zusammenfassung |
| Future space missions to globally map atmospheric carbon dioxide (CO2) at all latitudes
during the day and night, such as the ASCENDS (Active Sensing of CO2 Emissions over
Night, Day, and Seasons) mission, will require high-precision laser measurements of CO2
columns across the troposphere from low Earth orbit. This paper discusses the development
and measurement validation of a unique, multi-frequency, single-beam, laser absorption
spectrometer (LAS) that operates at 1.57 μm, which has been developed for a future
space-based mission to determine the global distribution of regional-scale CO2 sources and
sinks. A prototype of this space-based LAS system was developed by ITT, and it has
been flight tested in eight airborne campaigns conducted over the last five years in
Oklahoma, Michigan, New Hampshire, and Virginia under a wide range of atmospheric
conditions.
This paper focuses on the results obtained during the last two years of flight testing where
the remote LAS measurements of CO2 were evaluated against high-quality airborne in situ
CO2 measurements made on spirals near the center of the LAS flight tracks. Flight tests over
various land and water regions of Virginia in October 2007 showed the high correlation
(R2 = 0.995) of the LAS-measured CO2 optical depths (ODs) with altitude, and a
high correlation (R2 = 0.996) between the remote and in situ-derived (modeled)
CO2 ODs. The average difference between measured and modeled ODs was less
than 0.33% or the equivalent of about 1.25 ppmv of CO2. The LAS measurement
precision for a 10-s (1 km) average over land was found to be better than 0.7 ppmv and
over water was better than 1.4 ppmv. During the flight tests in September-October
2008, improvements in the in situ sampling strategy were implemented, and the
average difference between the measured and modeled CO2 ODs was found to be
0.11% or 0.42 ppmv. A comprehensive multiple-aircraft flight test program was
conducted over Oklahoma and Virginia in July-August 2009, and this resulted in an
average difference between the remote and in situ CO2 ODs for all six flights at all
altitudes of 0.10% or 0.40 ppmv with a standard deviation of the results of 0.64% or
2.5 ppmv. LAS instrument improvements also led to a 10-s CO2 measurement
precision over land of better than 0.2 ppmv and over water of better than 0.3 ppmv.
These high-precision, high-accuracy active remote CO2 measurements represent a
major step towards the realization of the needed capability for space-based laser
measurements of the global distribution of CO2. Details of the LAS flight tests and
comparisons of the observed and modeled CO2 measurements are discussed in this paper. |
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