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| Titel |
Assesment of Independent Macrophysical Cloud Properties in the Oxygen A-Band |
| VerfasserIn |
O. Schuessler, D. Loyola, A. Doicu, R. Spurr |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250067093
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| Zusammenfassung |
| Precise information about clouds is of high importance for the retrieval of atmospheric trace
gases, especially in the troposphere. In this work, we investigate the number of
independent macrophysical cloud properties that can be retrieved from the O2 A-band, in
the context of trace gas retrievals. The cloud parameter retrieval assumes a single
homogeneous cloud layer characterized by fractional cloud cover, cloud-top height,
cloud geometrical thickness and cloud optical thickness. Additional information
required for cloud-property retrieval, includes the surface properties, the viewing
geometry and the pressure and temperature distribution. To assess the retrieval
feasibility, we use a set of simulated spectra in the wavelength range of 758-770 nm, for
different combinations of cloud, surface and geometry parameters. The inversion is
performed by using Tikhonov regularization with an a priori parameter choice method.
Values of the condition number, defined as the ratio between the largest and the
smallest values of the Jacobian matrix, are analyzed and the degree of ill-posedness is
evaluated for retrievals involving multiple (four, three and two parameters) and a single
cloud parameter. For four and three parameters, the high degree of ill-posedness and
the multiple minima of the cost function yield unreliable results. It is shown that
information contained in the O2 A-band spectra is enough to retrieve only two
independent cloud parameters. Best results are obtained for the joint retrieval of (a)
cloud-top height and cloud fraction, or (b) cloud top height and cloud optical thickness. |
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