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| Titel |
Retrieval of macrophysical cloud parameters from MIPAS: algorithm description |
| VerfasserIn |
J. Hurley, A. Dudhia, R. G. Grainger |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 4, no. 4 ; Nr. 4, no. 4 (2011-04-07), S.683-704 |
| Datensatznummer |
250001928
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| Publikation (Nr.) |
 copernicus.org/amt-4-683-2011.pdf |
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| Zusammenfassung |
The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard
ENVISAT has the potential to be particularly useful for studying high, thin
clouds, which have been difficult to observe in the past. This paper details
the development, implementation and testing of an optimal-estimation-type
retrieval for three macrophysical cloud parameters (cloud top height, cloud
top temperature and cloud extinction coefficient) from infrared spectra
measured by MIPAS. A preliminary estimation of a parameterisation of the
optical and geometrical filling of the measurement field-of-view by cloud is
employed as the first step of the retrieval process to improve the choice of
a priori for the macrophysical parameters themselves.
Preliminary application to single-scattering simulations indicates that the
retrieval error stemming from uncertainties introduced by noise and by a
priori variances in the retrieval process itself is small – although it
should be noted that these retrieval errors do not include the significant
errors stemming from the assumption of homogeneity and the non-scattering
nature of the forward model. Such errors are preliminarily and qualitatively
assessed here, and are likely to be the dominant error sources. The retrieval
converges for 99% of input cases, although sometimes fails to converge for
vetically-thin (<1 km) clouds. The retrieval algorithm is applied to MIPAS
data; the results of which are qualitatively compared with CALIPSO cloud top
heights and PARASOL cloud opacities. From comparison with CALIPSO cloud
products, it must be noted that the cloud detection method used in this
algorithm appears to potentially misdetect stratospheric aerosol layers as
cloud.
This algorithm has been adopted by the European Space Agency's "MIPclouds" project. |
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