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| Titel |
Tomographic retrieval of water vapour and temperature around polar mesospheric clouds using Odin-SMR |
| VerfasserIn |
O. M. Christensen, P. Eriksson, J. Urban, D. Murtagh, K. Hultgren, J. Gumbel |
| 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 ; 8, no. 5 ; Nr. 8, no. 5 (2015-05-06), S.1981-1999 |
| Datensatznummer |
250116356
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| Publikation (Nr.) |
 copernicus.org/amt-8-1981-2015.pdf |
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| Zusammenfassung |
A special observation mode of the Odin satellite provides the first
simultaneous measurements of water vapour, temperature and polar
mesospheric cloud (PMC) brightness over a large geographical area
while still resolving both horizontal and vertical structures in the
clouds and background atmosphere. The observation mode was
activated during June, July and August of 2010 and 2011, and
for latitudes between 50 and 82° N.
This paper focuses on the water vapour and temperature measurements
carried out with Odin's sub-millimetre radiometer (SMR). The
tomographic retrieval approach used provides water vapour and
temperature between 75 and 90 km with a vertical resolution of
about 2.5 km and a horizontal resolution of about
200 km. The precision of the measurements is estimated to
0.2 ppmv for water vapour and 2 K for temperature. Due to limited
information about the pressure at the measured altitudes, the
results have large uncertainties (> 3 ppmv) in the retrieved water
vapour. These errors, however, influence mainly the mean atmosphere
retrieved for each orbit, and variations around this mean are still
reliably captured by the measurements.
SMR measurements are performed using two different mixer chains,
denoted as frequency mode 19 and 13. Systematic differences between
the two frontends have been noted. A first comparison with the Solar
Occultation For Ice Experiment instrument (SOFIE) on-board the
Aeronomy of Ice in the Mesosphere (AIM) satellite and the Fourier
Transform Spectrometer of the Atmospheric Chemistry Experiment
(ACE-FTS) on-board SCISAT indicates that the measurements using the
frequency mode 19 have a significant low bias in both temperature
(> 15 K) and water vapour (> 0.5 ppmv), while the measurements
using frequency mode 13 agree with the other instruments considering
estimated errors.
PMC brightness data is provided by OSIRIS, Odin's other
sensor. Combined SMR and OSIRIS data for some example orbits is
considered. For these orbits, effects of PMCs on the water vapour
distribution are clearly seen. Areas depleted of water vapour are
found above layers with PMC, while regions of enhanced water vapour
due to ice particle sedimentation are primarily placed between and
under the clouds. |
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