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| Titel |
Assessment of water vapor isotopologue measurements by ACE-FTS and Odin-SMR |
| VerfasserIn |
Ralf Bauer, Patrick Sheese, Kaley Walker, Joachim Urban, Donal Murtagh, Chris Boone, Peter Bernath, Gloria Manney |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108106
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| Publikation (Nr.) |
 EGU/EGU2015-7837.pdf |
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| Zusammenfassung |
| Knowing the isotopic composition of trace gases can improve our understanding of
processes in the Earth’s atmosphere causing isotopic fractionation. In many studies,
isotopologue (molecules of identical chemical but different isotopic composition)
amounts are primarily discussed as δ values, which are defined relative to a standard,
e.g.:
( )
18 (VM RH182 O /VM RH162 O )
δ O (o) = (V-M-R–18-/V-M-R–16-)VSMOW–- 1 * 1000
H2 O H2 O
with VSMOW as Vienna Standard Mean Ocean Water. This study targets the water vapor
isotopologues H218O and H217O in the stratosphere and lower mesosphere using δ18O and
δ17O for the comparison.
Over the past decades, H218O and H217O profiles have been measured with
balloon-borne (e.g. FIRS-2, Mk IV) and space-borne (e.g. ATMOS/SL3) instruments. The
satellite instruments ACE-FTS (Atmospheric Chemistry Experiment - Fourier Transform
Spectrometer) on the Canadian satellite SCISAT and SMR (Sub-Millimetre Radiometer) on
the Swedish satellite Odin provide a significantly larger number of individual profiles with
global coverage. Both instruments are still operational and provide data products for more
than 10 years. Assessing their data quality is of key importance before conclusions can be
drawn from these results.
ACE-FTS on SCISAT is an infrared Fourier Transform Spectrometer with a high spectral
resolution of 0.02Âcm-1 and a spectral range from 750 to 4400Âcm-1. It measures using
solar occultation viewing geometry. SCISAT is in a high inclination orbit at an altitude of
650 km. It was launched in August 2003 and has been performing routine measurements
since February 2004.
SMR on Odin measures millimetre wave emissions from the atmosphere with a
1.1Âm telescope in the 486 to 581ÂGHz range with four tunable radiometers. Odin
was launched in February 2001 into a quasi-polar sun-synchronous orbit at about
600 km altitude. Spectral regions for the target trace gases are selected for SMR using
different measurement modes and thus not all retrieved species can be measured
simultaneously.
In order to perform the comparison between ACE-FTS and SMR H218O (using δ18O), a
maximum temporal difference of 5Âhours and a maximum spatial difference of
1000 km were selected as collocation criteria. We followed the respective data quality
recommendations for each data set. To avoid comparisons of air masses inside and outside the
polar vortex, we used sPV (scaled potential vorticity) from the GEOS-5 data assimilation
system interpolated to the location and time of each of the observations. For δ17O, this
approach is not applicable, as SMR does not measure H217O and H216O simultaneously. A
climatological comparison was performed instead. In addition to these satellite
intercomparisons, comparisons with other remote sensing data products are discussed. |
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