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| Titel |
Ice particle habit and surface roughness derived from PARASOL polarization measurements |
| VerfasserIn |
B. H. Cole, P. Yang, B. A. Baum, J. Riedi, L. C. Labonnote |
| 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 ; 14, no. 7 ; Nr. 14, no. 7 (2014-04-11), S.3739-3750 |
| Datensatznummer |
250118584
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| Publikation (Nr.) |
 copernicus.org/acp-14-3739-2014.pdf |
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| Zusammenfassung |
| Ice clouds are an important element in the radiative balance of the
earth's climate system, but their microphysical and optical
properties still are not well constrained, especially ice particle
habit and the degree of particle surface roughness. In situ
observations have revealed common ice particle habits and evidence
for surface roughness, but these observations are limited. An
alternative is to infer the ice particle shape and surface roughness
from satellite observations of polarized reflectivity since
they are sensitive to both particle shape and degree of
surface roughness. In this study an adding–doubling radiative
transfer code is used to simulate polarized reflectivity for nine
different ice habits and one habit mixture, along with 17 distinct
levels of the surface roughness. A lookup table (LUT) is
constructed from the simulation results and used to infer shape and
surface roughness from PARASOL satellite polarized reflectivity
data over the ocean. Globally, the retrievals yield a compact aggregate of columns
as the most commonly retrieved ice habit. Analysis of PARASOL data
from the tropics results in slightly more aggregates than in
midlatitude or polar regions. Some level of surface roughness is
inferred in nearly 70% of PARASOL data, with mean and median
roughness near σ = 0.2 and 0.15, respectively. Tropical
region analyses have 20% more pixels retrieved with particle
surface roughness than in midlatitude or polar regions. The global
asymmetry parameter inferred at a wavelength of 0.865 μm
has a mean value of 0.77 and a median value of 0.75. |
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