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| Titel |
Deriving polarization properties of desert-reflected solar spectra with PARASOL data |
| VerfasserIn |
W. Sun, R. R. Baize, C. Lukashin, Y. Hu |
| 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 ; 15, no. 13 ; Nr. 15, no. 13 (2015-07-15), S.7725-7734 |
| Datensatznummer |
250119897
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| Publikation (Nr.) |
 copernicus.org/acp-15-7725-2015.pdf |
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| Zusammenfassung |
| One of the major objectives of the Climate Absolute Radiance and Refractivity
Observatory (CLARREO) is to conduct highly accurate spectral observations to
provide an on-orbit inter-calibration standard for relevant Earth-observing
sensors with various channels. To calibrate an Earth-observing sensor's
measurements with the highly accurate data from the CLARREO, errors in the
measurements caused by the sensor's sensitivity to the polarization state of
light must be corrected. For correction of the measurement errors due to the
light's polarization, both the instrument's dependence on the incident
polarization state and the on-orbit knowledge of the polarization state of
light as a function of observed scene type, viewing geometry, and solar
wavelength are required. In this study, an algorithm for deriving the
spectral polarization state of solar light from the desert is reported. The
desert/bare land surface is assumed to be composed of two types of areas:
fine sand grains with diffuse reflection (Lambertian non-polarizer) and
quartz-rich sand particles with facets of various orientations
(specular-reflection polarizer). The Adding–Doubling Radiative Transfer
Model (ADRTM) is applied to integrate the atmospheric
absorption and scattering in the system. Empirical models are adopted in
obtaining the diffuse spectral reflectance of sands and the optical depth of
the dust aerosols over the desert. The ratio of non-polarizer area to
polarizer area and the angular distribution of the facet orientations are
determined by fitting the modeled polarization states of light to the
measurements at three polarized channels (490, 670, and 865 nm) by the
Polarization and Anisotropy of Reflectances for Atmospheric Science
instrument coupled with Observations from a Lidar (PARASOL). Based on this
physical model of the surface, the desert-reflected solar light's
polarization state at any wavelength in the whole solar spectra can be
calculated with the ADRTM. |
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