Atmospheric Chemistry and Physics
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2008
10.5194/acp-8-1937-2008
http://www.atmos-chem-phys.net/8/1937/2008/
http://www.atmos-chem-phys.net/8/1937/2008/acp-8-1937-2008.html
http://www.atmos-chem-phys.net/8/1937/2008/acp-8-1937-2008.pdf
1937
1948
2008-04-03
Comparison between early Odin-SMR, Aura MLS and CloudSat retrievals of cloud ice mass in the upper tropical troposphere
P. Eriksson
patrick.eriksson@chalmers.se
M. Ekström
B. Rydberg
D. L. Wu
R. T. Austin
D. P. Murtagh
Department of Radio and Space Science, Chalmers University of Technology, Gothenburg, Sweden
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA
Emerging microwave satellite techniques are expected to provide
improved global measurements of cloud ice mass. CloudSat, Aura MLS
and Odin-SMR fall into this category and early cloud ice retrievals
from these instruments are compared. The comparison follows the SMR
retrieval product and is made for partial ice water columns above
12 km. None of the retrievals shows a significant degree of false
cloud detections, the ratio between local mean values from the
instruments is fairly constant and a consistent view of the
geographical distribution of cloud ice is obtained. However,
important differences on the absolute levels exist, where the
overall mean is 9.6, 4.2 and 3.7 g m<sup>−2</sup> for CloudSat, SMR and MLS,
respectively. Assumptions about the particle size distribution (PSD)
are a consideration for all three instruments and constitute the
dominating retrieval uncertainty for CloudSat. The mean for
CloudSat when applying the same PSD as for MLS and SMR was estimated
to 6.3 g m<sup>−2</sup>. A second main consideration for MLS and SMR are the
effects caused by the poorer spatial resolution: a possible vertical
misplacement of retrieved values and an impact of cloud
inhomogeneities. The latter effect was found to be the dominating
retrieval uncertainty for SMR, giving a possible mean value range of
2.3–8.9 g m<sup>−2</sup>. The comparison indicates a common retrieval
accuracy in the order of 70%. Already this number should suffice
for improved validations of cloud ice parametrisation schemes in
atmospheric models, but a substantially better consistency between
the datasets should be attainable through an increased understanding
of main retrieval error sources.
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