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| Titel |
On the interpretation of an unusual in-situ measured ice crystal scattering phase function |
| VerfasserIn |
A. J. Baran, J.-F. Gayet, V. Shcherbakov |
| 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 ; 12, no. 19 ; Nr. 12, no. 19 (2012-10-15), S.9355-9364 |
| Datensatznummer |
250011509
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| Publikation (Nr.) |
 copernicus.org/acp-12-9355-2012.pdf |
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| Zusammenfassung |
In-situ Polar Nephelometer (PN) measurements of unusual ice
crystal scattering phase functions, obtained near the cloud-top of a
mid-latitude anvil cloud, at a temperature of about −58 °C, were
recently reported by Gayet et al. (2012). The ice crystal habits that
produced the phase functions consisted of aggregates of ice crystals and
aggregates of quasi-spherical ice particles. The diameters of the individual
quasi-spherical ice particles were estimated to be between about 15 μm
and 20 μm. The measured-averaged scattering phase functions were
featureless, at scattering angles less than about 100°, but an ice
bow-like feature was noted between the scattering angles of about 120°
to 160°. The estimated asymmetry parameter was 0.78 ± 0.04.
In this paper, the averaged scattering phase function is interpreted in
terms of a weighted habit mixture model. The model that provides the best
overall fit to the measured scattering phase function comprises of highly
distorted ten-element hexagonal ice aggregates and quasi-spherical ice
particles. The smaller quasi-spherical ice crystals are represented by
Chebyshev ice particles of order 3, and were assumed to have equivalent
spherical diameters of 24 μm. The asymmetry parameter of the best
overall model was found to be 0.79. It is argued that the Chebyshev-like ice
particles are responsible for the ice bow-like feature and mostly dominate
the scattered intensity measured by the PN. The results from this paper have
important implications for climate modelling (energy balance of anvils),
cloud physics and the remote sensing of cirrus properties. |
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