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| Titel |
Influence of ice particle model on satellite ice cloud retrieval: lessons learned from MODIS and POLDER cloud product comparison |
| VerfasserIn |
Z. Zhang, P. Yang, G. Kattawar, J. Riedi, L. C. Labonnote, B. A. Baum, S. Platnick, H.-L. Huang |
| 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 ; 9, no. 18 ; Nr. 9, no. 18 (2009-09-24), S.7115-7129 |
| Datensatznummer |
250007651
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| Publikation (Nr.) |
 copernicus.org/acp-9-7115-2009.pdf |
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| Zusammenfassung |
| The influence is investigated of the assumed ice particle microphysical and
optical model on inferring ice cloud optical thickness (τ) from
satellite measurements of the Earth's reflected shortwave radiance. Ice
cloud τ are inferred, and subsequently compared, using products from
MODIS (MODerate resolution Imaging Spectroradiometer) and POLDER
(POLarization and Directionality of the Earth's Reflectances). POLDER τ
values are found to be substantially smaller than those from collocated
MODIS data. It is shown that this difference is caused primarily by the use
of different ice particle bulk scattering models in the two retrievals, and
more specifically, the scattering phase function. Furthermore, the influence
of the ice particle model on the derivation of ice cloud radiative forcing
(CRF) from satellite retrievals is studied. Three sets of shortwave CRF are
calculated using different combinations of the retrieval and associated ice
particle models. It is shown that the uncertainty associated with an ice
particle model may lead to two types of errors in estimating CRF from
satellite retrievals. One stems from the retrieval itself and the other is
due to the optical properties, such as the asymmetry factor, used for CRF
calculations. Although a comparison of the CRFs reveals that these two types
of errors tend to cancel each other, significant differences are still found
between the three CRFs, which indicates that the ice particle model affects
not only optical thickness retrievals but also CRF calculations. In addition
to CRF, the effect of the ice particle model on the derivation of seasonal
variation of τ from satellite measurements is discussed. It is
shown that optical thickness retrievals based on the same MODIS
observations, but derived using different assumptions of the ice particle
model, can be substantially different. These differences can be divided into
two parts. The first-order difference is mainly caused by the differences in
the asymmetry factor. The second-order difference is related to seasonal
changes in the sampled scattering angles and therefore dependent on the
sun-satellite viewing geometry. Because of this second-order difference, the
use of different ice particle models may lead to a different understanding
of the seasonal variation of τ. |
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