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| Titel |
Retrieving simulated volcanic, desert dust and sea-salt particle properties from two/three-component particle mixtures using UV-VIS polarization lidar and T matrix |
| VerfasserIn |
G. David, B. Thomas, T. Nousiainen, A. Miffre, P. Rairoux |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 14 ; Nr. 13, no. 14 (2013-07-18), S.6757-6776 |
| Datensatznummer |
250018765
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| Publikation (Nr.) |
 copernicus.org/acp-13-6757-2013.pdf |
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| Zusammenfassung |
| During transport by advection, atmospheric nonspherical particles, such as
volcanic ash, desert dust or sea-salt particles experience several chemical
and physical processes, leading to a complex vertical atmospheric layering at
remote sites where intrusion episodes occur. In this paper, a new methodology
is proposed to analyse this complex vertical layering in the case of a
two/three-component particle external mixtures. This methodology relies on an
analysis of the spectral and polarization properties of the light
backscattered by atmospheric particles. It is based on combining a sensitive
and accurate UV-VIS polarization lidar experiment with T-matrix numerical
simulations and air mass back trajectories. The Lyon UV-VIS polarization
lidar is used to efficiently partition the particle mixture into its
nonspherical components, while the T-matrix method is used for simulating the
backscattering and depolarization properties of nonspherical volcanic ash,
desert dust and sea-salt particles. It is shown that the particle mixtures'
depolarization ratio δ p differs from the nonspherical
particles' depolarization ratio δns due to the presence of
spherical particles in the mixture. Hence, after identifying a tracer for
nonspherical particles, particle backscattering coefficients specific to each
nonspherical component can be retrieved in a two-component external mixture.
For three-component mixtures, the spectral properties of light must in
addition be exploited by using a dual-wavelength polarization lidar. Hence,
for the first time, in a three-component external mixture, the nonsphericity
of each particle is taken into account in a so-called 2β + 2δ
formalism. Applications of this new methodology are then demonstrated in two
case studies carried out in Lyon, France, related to the mixing of
Eyjafjallajökull volcanic ash with sulfate particles (case of a
two-component mixture) and to the mixing of dust with sea-salt and
water-soluble particles (case of a three-component mixture). This new
methodology, which is able to provide separate vertical profiles of
backscattering coefficient for mixed atmospheric dust, sea-salt and
water-soluble particles, may be useful for accurate radiative forcing
assessments. |
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