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| Titel |
What is the benefit of ceilometers for aerosol remote sensing? An answer from EARLINET |
| VerfasserIn |
M. Wiegner, F. Madonna, I. Binietoglou, R. Forkel, J. Gasteiger, A. Geiß, G. Pappalardo, K. Schäfer, W. Thomas |
| 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 ; 7, no. 7 ; Nr. 7, no. 7 (2014-07-03), S.1979-1997 |
| Datensatznummer |
250115838
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| Publikation (Nr.) |
 copernicus.org/amt-7-1979-2014.pdf |
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| Zusammenfassung |
| With the establishment of ceilometer networks by national weather services,
a discussion commenced to which extent these simple backscatter lidars can be
used for aerosol research. Though primarily designed for the detection of
clouds it was shown that at least observations of the vertical structure of
the boundary layer might be possible. However, an assessment of the potential
of ceilometers for the quantitative retrieval of aerosol properties is still
missing. In this paper we discuss different retrieval methods to derive the
aerosol backscatter coefficient βp, with special focus on the
calibration of the ceilometers. Different options based on forward and
backward integration methods are compared with respect to their accuracy and
applicability. It is shown that advanced lidar systems such as those being operated in
the framework of the European Aerosol Research Lidar Network (EARLINET) are
excellent tools for the calibration, and thus βp retrievals
based on forward integration can readily be implemented and used for real-time applications. Furthermore, we discuss uncertainties introduced by
incomplete overlap, the unknown lidar ratio, and water vapor absorption. The
latter is relevant for the very large number of ceilometers operating in the
spectral range around λ = 905–910 nm. The accuracy of the
retrieved βp mainly depends on the accuracy of the
calibration and the long-term stability of the ceilometer. Under favorable
conditions, a relative error of βp on the order of 10%
seems feasible. In the case of water vapor absorption, corrections assuming a
realistic water vapor distribution and laser spectrum are indispensable;
otherwise errors on the order of 20% could occur. From case studies it is
shown that ceilometers can be used for the reliable detection of elevated
aerosol layers below 5 km, and can contribute to the validation of chemistry
transport models, e.g., the height of the boundary layer. However, the
exploitation of ceilometer measurements is still in its infancy, so more
studies are urgently needed to consolidate the present state of knowledge,
which is based on a limited number of case studies. |
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