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Properties of semitransparent upper-level clouds deduced from multispectral imagery data

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dc.contributor.advisor Coakley, James A. Jr
dc.creator Lin, Xijian
dc.date.accessioned 2012-04-11T15:33:12Z
dc.date.available 2012-04-11T15:33:12Z
dc.date.copyright 1996-04-23
dc.date.issued 1996-04-23
dc.identifier.uri http://hdl.handle.net/1957/28696
dc.description Graduation date: 1996 en_US
dc.description.abstract A multispectral retrieval method is developed on the 100 km regional scale to extract the temperature, particle size, fractional cover and 11-μm emissivity of clouds which may be semitransparent in the infrared based on emitted radiances. The scheme utilizes the nonlinear relationship between emitted radiances when clouds are semitransparent and form a single-layered system. The retrieval method has the limitation that the particle size must be sufficiently small that the extinction and absorption cross sections at the different wavelengths are significantly different. For combinations of emission at 11 and 12 μm, the droplets must have radii less than 20 μm for both ice and water; for 3.7 and 12 μm the droplets must have radii less than 60 μm for ice and less than 100 μm for water; for 3.7 and 8 μm the droplets must have radii less than l50 μm for both ice and water. The retrieval scheme together with the spatial coherence method is applied to the analysis of NOAA-11 4-km Advanced Very High Resolution Radiometer 3.7, 11 and 12-μm observations obtained during the First ISCCP Regional Experiment Intensive Field Observations, Kansas, 1991. The results indicate that clear skies, single-layered and multi-layered cloud systems constitute equal proportions of 100-km scale regions. For the upper-level, single-layered clouds, 100-km scale emissivity and fractional cloud cover are correlated and the average effective radius of ice particles in semitransparent clouds is about 10 μm. Numerical simulations are performed to determine the sensitivity of the retrieved results to errors in observations and model assumptions and to compare the results of the current algorithm to those obtained with a threshold algorithm like that used by ISCCP. For effective radii less than 15 μm, errors in the retrieved effective radius are less than 1.5 μm and errors in cloud temperature are less than 5 K. The fractional cloud cover may be underestimated by 0.15. The 11-μm emissivity may be overestimated by 0.30. For upper-level, semitransparent/broken clouds, the current algorithm is superior to the threshold algorithm in the determination of cloud temperature and effective radius. en_US
dc.language.iso en_US en_US
dc.subject.lcsh Clouds -- Remote sensing en_US
dc.subject.lcsh Atmospheric radiation en_US
dc.title Properties of semitransparent upper-level clouds deduced from multispectral imagery data en_US
dc.type Thesis/Dissertation en_US
dc.degree.name Doctor of Philosophy (Ph. D.) in Atmospheric Sciences en_US
dc.degree.level Doctoral en_US
dc.degree.discipline Oceanic and Atmospheric Sciences en_US
dc.degree.grantor Oregon State University en_US
dc.contributor.committeemember Abbott, Mark
dc.contributor.committeemember Strub, Ted
dc.contributor.committeemember Unsworth, Michael H.
dc.contributor.committeemember Vong, Richard J.
dc.description.digitization File scanned at 300 ppi (Monochrome, 8-bit Grayscale) using ScandAll PRO 1.8.1 on a Fi-6670 in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR. en_US
dc.description.peerreview no en_us


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