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| Titel |
ARIS-Campaign: intercomparison of three ground based 22 GHz radiometers for middle atmospheric water vapor at the Zugspitze in winter 2009 |
| VerfasserIn |
C. Straub, A. Murk, N. Kämpfer, S. H. W. Golchert, G. Hochschild, K. Hallgren, P. Hartogh |
| 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. 9 ; Nr. 4, no. 9 (2011-09-22), S.1979-1994 |
| Datensatznummer |
250002102
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| Publikation (Nr.) |
 copernicus.org/amt-4-1979-2011.pdf |
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| Zusammenfassung |
This paper presents the Alpine Radiometer Intercomparison at the
Schneefernerhaus (ARIS), which took place in winter 2009 at the high altitude
station at the Zugspitze, Germany (47.42° N, 10.98° E,
2650 m). This campaign was the first direct intercomparison between three
new ground based 22 GHz water vapor radiometers for middle atmospheric
profiling with the following instruments participating: MIRA 5 (Karlsruhe
Institute of Technology), cWASPAM3 (Max Planck Institute for Solar System
Research, Katlenburg-Lindau) and MIAWARA-C (Institute of Applied Physics,
University of Bern). Even though the three radiometers all measure middle
atmospheric water vapor using the same rotational transition line and similar
fundamental set-ups, there are major differences between the front ends, the
back ends, the calibration concepts and the profile retrieval.
The spectrum comparison shows that all three radiometers measure spectra without severe
baseline artifacts and that the measurements are in good general agreement.
The measurement noise shows good agreement to the values theoretically expected
from the radiometer noise formula. At the same time the comparison of the noise
levels shows that there is room for instrumental and calibration improvement,
emphasizing the importance of low elevation angles for the observation, a low receiver noise temperature and an efficient calibration scheme.
The comparisons of the retrieved profiles show that the agreement between the
profiles of MIAWARA-C and cWASPAM3 with the ones of MLS is better than
0.3 ppmv (6%) at all altitudes. MIRA 5 has a dry bias of approximately
0.5 ppm (8%) below 0.1 hPa with respect to all other instruments.
The profiles of cWASPAM3 and MIAWARA-C could not be directly compared because
the vertical region of overlap was too small. The comparison of the time
series at different altitude levels show a similar evolution of the H2O
volume mixing ratio (VMR) for the ground based instruments as well as the
space borne sensor MLS. |
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