26 February 2004 Sea surface emissivity angular measurements: comparison with theoretical models
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Abstract
The current request of a minimum precision of ± 0.3 K in the sea surface temperature for climate studies and the use of high observation angles in the present space missions require a thorough analysis of sea surface emissivity (SSE) and its angular dependence. In this paper, we present SSE experimental values determined from thermal infrared radiometric measurements carried out from an oilrig under open Mediterranean conditions during the WInd and Salinity Experiment 2000 campaign (WISE 2000) founded by ESA. The methodology consists of quasi-simultaneous measurements of the radiance coming from the sea surface and the downwelling sky radiance, in addition to the corresponding sea temperature as reference. Radiometric data were taken by a CE 312 radiometer, with 4 channels placed in the 8-14 μm interval. Sea temperature was measured with high-precision thermal probes located on oceanographic buoys. SSE was obtained under several observation angles and surface wind speed conditions, allowing us to study both angular and sea surface roughness dependence. SSE decreases 2% - 3% for 55°. Finally, we compare our results with several theoretical models, showing the validity of the Masuda et al. (1988) model for observation angles up to 50°. For higher angles, the effect of possible double or multiple reflections on the sea surface produces discrepancies between measured and theoretical SSEs, such as Wu and Smith (1997) advised.
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Raquel R. Niclos, Enric Valor, Vicente Caselles, Cesar Coll, "Sea surface emissivity angular measurements: comparison with theoretical models", Proc. SPIE 5233, Remote Sensing of the Ocean and Sea Ice 2003, (26 February 2004); doi: 10.1117/12.512377; https://doi.org/10.1117/12.512377
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