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Atmospheric Chemistry and Physics, 8, 4741-4757, 2008.
Remote sensing of cloud sides of deep convection: towards a
three-dimensional retrieval of cloud particle size profiles.
Tobias Zinner, Alexander Marshak, Stephen Lang, J. Vanderlei Martins, and Bernhard Mayer
Abstract
The cloud scanner sensor is a central part of a recently proposed satellite remote sensing concept -
the three dimensional (3D) cloud and aerosol interaction mission (CLAIM-3D) combining measurements of
aerosol characteristics in the vicinity of clouds and profiles of cloud microphysical characteristics.
Such a set of collocated measurements will allow new insights in the complex field of cloudaerosol
interactions affecting directly the development of clouds and precipitation, especially in convection.
The cloud scanner measures radiance reflected or emitted by cloud sides at several wavelengths to derive
a profile of cloud particle size and thermodynamic phase. For the retrieval of effective size a Bayesian
approach was adopted and introduced in a preceding paper.
In this paper the potential of the approach, which has to account for the complex three-dimensional
nature of cloud geometry and radiative transfer, is tested in realistic cloud observing situations.
In a fully simulated environment realistic cloud resolving modelling provides complex 3D structures of
ice, water, and mixed phase clouds, from the early stage of convective development to mature deep convection.
A three-dimensional Monte Carlo radiative transfer is used to realistically simulate the aspired observations.
A large number of cloud data sets and related simulated
observations provide the database for an experimental Bayesian retrieval. An independent simulation of an
additional cloud field serves as a synthetic test bed for the demonstration of the capabilities of the
developed retrieval techniques. For this test case only a minimal overall bias in the
order of 1% as well as pixel-based uncertainties in the order of 1 micron for droplets and 8 micron for
ice particles were found for measurements at a high spatial resolution of 250 m.
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