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| Titel |
Correction of water vapor absorption for aerosol remote sensing with ceilometers |
| VerfasserIn |
M. Wiegner, J. Gasteiger |
| 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. 9 ; Nr. 8, no. 9 (2015-09-30), S.3971-3984 |
| Datensatznummer |
250116589
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| Publikation (Nr.) |
 copernicus.org/amt-8-3971-2015.pdf |
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| Zusammenfassung |
| In recent years attention was increasingly paid to backscatter profiles of
ceilometers as a new source of aerosol information. Several case studies have
shown that – although originally intended for cloud detection only – ceilometers
can provide the planetary boundary layer height and even
quantitative information such as the aerosol backscatter coefficient
βp, provided that the signals have been calibrated. It is
expected that the retrieval of aerosol parameters will become widespread as
the number of ceilometers is steadily increasing, and continuous and
unattended operation is provided. In this context however one should be aware
of the fact that the majority of ceilometers provides signals that are
influenced by atmospheric water vapor. As a consequence, profiles of aerosol
parameters can only be retrieved if water vapor absorption is taken into
account. In this paper we describe the influence of water vapor absorption on
ceilometer signals at wavelengths around
λ = 910 nm. Spectrally high-resolved absorption coefficients are
calculated from HITRAN on the basis of realistic emission spectra of
ceilometers. These results are used as a reference to develop a methodology
("WAPL") for routine and near-real time corrections of the water vapor
influence. Comparison of WAPL with the reference demonstrates its very high
accuracy. Extensive studies with simulations based on measurements reveal
that the error when water vapor absorption is ignored in the
βp-retrieval can be in the order of 20 % for mid-latitudes
and more than 50 % for the tropics. It is concluded that the emission
spectrum of the laser source should be provided by the manufacturer to
increase the accuracy of WAPL, and that 910 nm is better suited than
905 nm. With WAPL systematic errors can be avoided, that would exceed the
inherent errors of the Klett solutions by far. |
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