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Radiative Transfer in Highly Variable Cloud Scenarios
Sebastián Gimeno García(1), Victor Venema(2) and Thomas Trautmann(1) (1) DLR, Münchenerstr. 20, 82234 Oberpfaffenhofen, Germany
(2) University of Bonn, Auf dem Huegel 20, 53121 Bonn, Germany
Abstract
New technologies permit going continuously down into the spatial
scale when observing the Earth's atmosphere from spaceborne
instruments. At the same time, new computers are equipped with large
main memories that allow to allocate bigger data arrays of optical
properties.
Historically, strongly approximative approaches have being used for
the computation of the radiative transfer in remote sensing and
climate/weather modeling applications. The main reasons are: On the one
hand, to keep the computational time and memory save under some
required limit, and on the other hand, to come up with easy-to-use
analytical expressions that simplify the inversion process.
The new generation of applications will have to deal with more
complexity in optical fields and with the general solution of the
radiative transfer in order to be able to reproduce the real radiance
and flux fields.
Within this scenario, we present results of the "exact" radiative
transfer through high spatially resolved stochastically generated
cloud fields embedded in realistic atmospheres. For this purpose, a
versatile three-dimensional radiative transfer Monte Carlo code
(MoCaRT) together with a robust cloud generator (IAAFT) able to add
subscale variability have been used. The "exact" results are compared
with those obtained using restrictive methods such as plane parallel and
independent pixel approximations. The differences and deficiencies
of these approximations are pointed out.
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