Microwave radiometric observation of sea surface from aircraft. Comparison of observed and the oretically predicted brigthness temperatures.:Comparison of observed and the oretically predicted brigthness temperatures
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This paper introduces the process of theoretical prediction of brightness temperature and the analysis of the brightness temperature observed from aircraft, taking into account aircraft attitude and radiometric corrections. Microwave radiometric observations were made from aircraft at the two heights of 300 and 2000m above the sea level in Kii Strait in November 10-12, 1987. Microwave frequencies used are 6.7 and 18.6 GHz. The beamwidths of the two radiometers employed are about 9 degrees.<BR>Observed brightness terperature was, at first, compared with the theoretically predicted one which is an averaged brightness temperature over the boresight beamwidth of 30 degrees and is only due to sea surface emission (free from surface reflection and sky radiation). The former was larger than the latter over entire angular range of incidence in both polarizations at both frequencies. Next, the observed brightness temperature was compared with the theoretically predicted one, considering radiations coming from all directions, i.e. the sea surface and the sky. The sea surface reflection of the downwelling sky radiation was also considered. This correction leads to good agreement between observation and theoretical prediction, and the surface reflection is of significant effect to the observed brightness temperature. Finally, main-lobe-averaged brightness temperature only due to the inherent sea surface emission was also retrieved from the observed one, incorporating the surface reflection and side lobe effect corrections. The retrieved results agreed with the theoretical predictions. The retrieved results agreed with the theoretical predictions within 3K over entire incidence angle in both polarizations at both frequencies.
- 社団法人 日本リモートセンシング学会の論文