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| Titel |
Investigation of ground-based microwave radiometer calibration techniques at 530 hPa |
| VerfasserIn |
G. Maschwitz, U. Löhnert, S. Crewell, T. Rose, D. D. Turner |
| 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 ; 6, no. 10 ; Nr. 6, no. 10 (2013-10-15), S.2641-2658 |
| Datensatznummer |
250085080
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| Publikation (Nr.) |
 copernicus.org/amt-6-2641-2013.pdf |
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| Zusammenfassung |
| Ground-based microwave radiometers (MWR) are becoming more and more common
for remotely sensing the atmospheric temperature and humidity profile as
well as path-integrated cloud liquid water content. The calibration accuracy
of the state-of-the-art MWR HATPRO-G2 (Humidity And Temperature Profiler – Generation 2)
was investigated during the second phase of the Radiative
Heating in Underexplored Bands Campaign (RHUBC-II) in northern Chile (5320 m
above mean sea level, 530 hPa) conducted by the Atmospheric Radiation
Measurement (ARM) program conducted between August and October 2009. This
study assesses the quality of the two frequently used liquid nitrogen and
tipping curve calibrations by performing a detailed error propagation study,
which exploits the unique atmospheric conditions of RHUBC-II. Both methods
are known to have open issues concerning systematic offsets and calibration
repeatability. For the tipping curve calibration an uncertainty of
±0.1 to ±0.2 K (K-band) and ±0.6 to
±0.7 K (V-band) is found. The uncertainty in the tipping curve
calibration is mainly due to atmospheric inhomogeneities and the assumed air
mass correction for the Earth curvature. For the liquid nitrogen calibration
the estimated uncertainty of ±0.3 to ±1.6 K is
dominated by the uncertainty of the reflectivity of the liquid nitrogen
target. A direct comparison between the two calibration techniques shows that
for six of the nine channels that can be calibrated with both methods, they agree
within the assessed uncertainties. For the other three channels the
unexplained discrepancy is below 0.5 K. Systematic offsets, which
may cause the disagreement of both methods within their estimated
uncertainties, are discussed. |
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