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| Titel |
Parameterization of single-scattering properties of snow |
| VerfasserIn |
P. Räisänen, A. Kokhanovsky, G. Guyot, O. Jourdan, T. Nousiainen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 9, no. 3 ; Nr. 9, no. 3 (2015-06-23), S.1277-1301 |
| Datensatznummer |
250116816
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| Publikation (Nr.) |
 copernicus.org/tc-9-1277-2015.pdf |
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| Zusammenfassung |
| Snow consists of non-spherical grains of various shapes and
sizes. Still, in many radiative transfer applications,
single-scattering properties of snow have been based on the assumption
of spherical grains. More recently, second-generation Koch fractals
have been employed. While they produce a relatively flat phase
function typical of deformed non-spherical particles, this is still
a rather ad hoc choice. Here, angular scattering measurements for
blowing snow conducted during the CLimate IMpacts of Short-Lived
pollutants In the Polar region (CLIMSLIP) campaign at Ny Ålesund,
Svalbard, are used to construct a reference phase function for
snow. Based on this phase function, an optimized habit combination
(OHC) consisting of severely rough (SR) droxtals, aggregates of SR
plates and strongly distorted Koch fractals is selected. The
single-scattering properties of snow are then computed for the OHC as
a function of wavelength λ and snow grain volume-to-projected
area equivalent radius rvp. Parameterization equations are
developed for λ = 0.199–2.7 μm and
rvp = 10–2000 μm, which express the
single-scattering co-albedo β, the asymmetry parameter g and
the phase function P11 as functions of the size parameter and the
real and imaginary parts of the refractive index. The
parameterizations are analytic and simple to use in radiative transfer
models. Compared to the reference values computed for the OHC, the
accuracy of the parameterization is very high for β and
g. This is also true for the phase function parameterization, except
for strongly absorbing cases (β > 0.3). Finally, we consider
snow albedo and reflected radiances for the suggested snow optics
parameterization, making comparisons to spheres and distorted Koch fractals. |
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