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| Titel |
Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements |
| VerfasserIn |
J. Gasteiger, V. Freudenthaler |
| 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. 11 ; Nr. 7, no. 11 (2014-11-17), S.3773-3781 |
| Datensatznummer |
250115950
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| Publikation (Nr.) |
 copernicus.org/amt-7-3773-2014.pdf |
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| Zusammenfassung |
A better quantification of aerosol properties is required for improving the
modelling of aerosol effects on weather and climate. This task is
methodologically demanding due to the diversity of the microphysical
properties of aerosols and the complex relation between their microphysical
and optical properties. Advanced lidar systems provide spatially and
temporally resolved information on the aerosol optical properties that is
sufficient for the retrieval of important aerosol microphysical properties.
Recently, the mass concentration of transported volcanic ash, which is
relevant for the flight safety of aeroplanes, was retrieved from measurements
of such lidar systems in southern Germany. The relative uncertainty of the
retrieved mass concentration was on the order of ±50%.
The present study investigates improvements of the retrieval accuracy when
the capability of measuring the linear depolarization ratio at 1064 nm is
added to the lidar setup. The lidar setups under investigation are based on
those of MULIS and POLIS of the Ludwig-Maximilians-Universität in
Munich (Germany) which measure the linear depolarization ratio at 355 and
532 nm with high accuracy. The improvements are determined by comparing
uncertainties from retrievals applied to simulated measurements of this lidar
setup with uncertainties obtained when the depolarization at 1064 nm is
added to this setup. The simulated measurements are based on real lidar
measurements of transported Eyjafjallajökull volcano ash. It is found that
additional 1064 nm depolarization measurements significantly reduce the
uncertainty of the retrieved mass concentration and effective particle size.
This significant improvement in accuracy is the result of the increased
sensitivity of the lidar setup to larger particles. The size dependence of
the depolarization does not vary strongly with refractive index, thus we
expect similar benefits for the retrieval in case of measurements of other volcanic ash
compositions and also for transported desert dust. For the retrieval of the
single scattering albedo, which is relevant to the radiative transfer in
aerosol layers, no significant improvements were found. |
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