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The Clouds and the Earth's Radiant Energy System (CERES) Inversion
Working Group is responsible for determining instantaneous
top-of-atmosphere (TOA) shortwave (SW), longwave (LW) and window (WN)
unfiltered radiances and fluxes from filtered SW, total (TOT) and WN
channel radiances measured by the CERES instrument.
The methodology for determining unfiltered
radiances is described in Loeb et al. (2001). To convert unfiltered
radiances to TOA fluxes, empirical angular distribution models (ADMs)
are developed from several months of CERES radiance measurements. To
optimize angular sampling, the CERES instrument operates in a rotating
azimuth plane (RAP) scan. In this mode, the instrument rotates in
azimuth as it scans in elevation. CERES can also scan in a fixed
azimuth plane, both in cross-track and along-track directions. Flying
along with CERES is a high-resolution imager capable of measuring
radiances in several narrow spectral channels. On TRMM, the imager is
the Visible Infrared Scanner (VIRS); on Terra and Aqua, the imager is
the Moderate-resolution Imaging Spectroradiometer (MODIS).
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Information from both the imager and CERES are used to develop
ADMs. The ADMs are determined by compositing radiances acquired over
several months sorted by sun-earth-satellite viewing geometry. The
ADMs are defined as a function of imager-derived parameters that have
the greatest influence on the anisotropy (or angular dependence) of
the scene radiances (e.g. surface type, cloud phase, cloud optical
depth etc).
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This web site provides images and tables of ADMs for each instrument
and CERES channel. It also provides results from key validation
studies and shows publications and conference presentations from members
within the CERES Inversion Working Group.
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Loeb, N.G., K.J. Priestley, D.P. Kratz, E.B. Geier, R.N. Green,
B.A. Wielicki, P.O'R. Hinton, and S.K. Nolan, 2001: Determination of
unfiltered radiances from the Clouds and the Earth's Radiant Energy
System (CERES) instrument. J. Appl. Meteor., 40, 822-835.
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