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Validation of cloud property retrievals with simulated satellite radiances: a case study for SEVIRI

Bugliaro, Luca and Zinner, T. and Keil, C. and Mayer, B. and Hollmann, R. and Reuter, M. and Thomas, W. (2011) Validation of cloud property retrievals with simulated satellite radiances: a case study for SEVIRI. Atmospheric Chemistry and Physics, 11, pp. 5603-5624. DOI: 10.5194/acp-11-5603-2011.

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Official URL: http://www.atmos-chem-phys.net/11/5603/2011/

Abstract

Validation of cloud properties retrieved from passive spaceborne imagers is essential for cloud and climate applications but complicated due to the large differences in scale and observation geometry between the satellite footprint and the independent ground based or airborne observations. Here we illustrate and demonstrate an alternative approach: starting from the output of the COSMOEU weather model of the German Weather Service realistic three-dimensional cloud structures at a spatial scale of 2.33 km are produced by statistical downscaling and microphysical properties are associated to them. The resulting data sets are used as input to the one-dimensional radiative transfer model libRadtran to simulate radiance observations for all eleven low resolution channels of MET-8/SEVIRI. At this point, both cloud properties and satellite radiances are known such that cloud property retrieval results can be tested and tuned against the objective input �truth�. As an example, we validate a cloud property retrieval of the Institute of Atmospheric Physics of DLR and that of EUMETSAT�s Climate Monitoring Science Application Facility CMSAF. Cloud detection and cloud phase assignment perform well. By both retrievals 88% of the pixels are correctly classified as clear or cloudy. The DLR algorithm assigns the correct thermodynamic phase to 95% of the cloudy pixels and the CMSAF retrieval to 84%. Cloud top temperature is slightly overestimated by the DLR code (+3.1K mean difference with a standard deviation of 10.6 K) and to a very low extent by the CMSAF code (�0.12K with a standard deviation of 7.6 K).Both retrievals account reasonably well for the distribution of optical thickness for both water and ice clouds, with a tendency to underestimation. Cloud effective radii are most difficult to evaluate but the APICS algorithm shows that realistic histograms of occurrences can be derived (CMSAF was not evaluated in this context). Cloud water path, which is a combination of the last two quantities, is slightly underestimated by APICS, while CMSAF shows a larger scattering.

Document Type:Article
Title:Validation of cloud property retrievals with simulated satellite radiances: a case study for SEVIRI
Authors:
AuthorsInstitution or Email of Authors
Bugliaro, LucaDLR
Zinner, T.LMU, München
Keil, C.LMU, München
Mayer, B.DLR/LMU, München
Hollmann, R.DWD, Offenbach am Main
Reuter, M.Univ of Bremen, Bremen
Thomas, W.Univ of Bremen, Bremen
Date:2011
Journal or Publication Title:Atmospheric Chemistry and Physics
Refereed publication:Yes
In Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:11
DOI:10.5194/acp-11-5603-2011
Page Range:pp. 5603-5624
Status:Published
Keywords:COSMOEU
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Erdbeobachtung
DLR - Research theme (Project):R - Vorhaben Atmosphären- und Klimaforschung
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Remote Sensing
Deposited By: Jana Freund
Deposited On:07 Dec 2011 16:42
Last Modified:12 Dec 2013 21:28

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