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| Titel |
Next-generation angular distribution models for top-of-atmosphere radiative flux calculation from CERES instruments: methodology |
| VerfasserIn |
W. Su, J. Corbett, Z. Eitzen, L. Liang |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 2 ; Nr. 8, no. 2 (2015-02-05), S.611-632 |
| Datensatznummer |
250116124
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| Publikation (Nr.) |
 copernicus.org/amt-8-611-2015.pdf |
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| Zusammenfassung |
| The top-of-atmosphere (TOA) radiative fluxes are critical components to
advancing our understanding of the Earth's radiative energy balance,
radiative effects of clouds and aerosols, and climate feedback. The Clouds
and the Earth's Radiant Energy System (CERES) instruments provide broadband
shortwave and longwave radiance measurements. These radiances are converted
to fluxes by using scene-type-dependent angular distribution models (ADMs).
This paper describes the next-generation ADMs that are developed for
Terra and Aqua using all available CERES rotating azimuth
plane radiance measurements. Coincident cloud and aerosol retrievals, and
radiance measurements from the Moderate Resolution Imaging Spectroradiometer
(MODIS), and meteorological parameters from Goddard Earth Observing System
(GEOS) data assimilation version 5.4.1 are used to define scene type. CERES
radiance measurements are stratified by scene type and by other parameters
that are important for determining the anisotropy of the given scene type.
Anisotropic factors are then defined either for discrete intervals of
relevant parameters or as a continuous functions of combined parameters,
depending on the scene type. Significant differences between the ADMs
described in this paper and the existing ADMs are over clear-sky scene types
and polar scene types. Over clear ocean, we developed a set of shortwave (SW)
ADMs that explicitly account for aerosols. Over clear land, the SW ADMs are
developed for every 1° latitude × 1° longitude region
for every calendar month using a kernel-based bidirectional reflectance model.
Over clear Antarctic scenes, SW ADMs are developed by accounting the effects of
sastrugi on anisotropy. Over sea ice, a sea-ice brightness index is used to
classify the scene type. Under cloudy conditions over all surface types, the
longwave (LW) and window (WN) ADMs are developed by combining surface and
cloud-top temperature, surface and cloud emissivity, cloud fraction, and
precipitable water. Compared to the existing ADMs, the new ADMs change the
monthly mean instantaneous fluxes by up to 5 W m−2 on a regional scale of
1° latitude × 1° longitude, but the flux changes are
less than 0.5 W m−2 on a global scale. |
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