The visible light reflected from a wind-roughened sea surface contains information about the sea state in the form of its polarisation status. Each sea state is characterised by a specific wave-slope distribution depending upon the nature of surface winds. This in turn, imparts unique polarisation characteristics to the light reflected from a wind-roughened sea surface in accordance with Fresnel's reflection laws as established by earlier studies. In this paper, we discuss the significance of surface reflected light in the context of using it for remote sensing of sea state. We propose the design for an instrument that will view the wind-roughened sea surface over a period of time and compute the fraction of plane polarised light received by it. The results then can be related to the sea state and the wind speed prevailing over the sea. The instrument can be made to view the sea surface at any look angle though the angles in the range of 30-40 and 65-70 degrees are found to be preferable for better resolution of sea states. The proposed instrument can be mounted on an observation tower, aircraft or a satellite. The range of wind speeds that can be sensed by the proposed instrument is 0-60 knots.
Accurate retrieval of air-sea exchange parameters from satellite is highly desirable
as it contributes immensely to the understanding of climate change. Due to the inherent
difficulties in the direct flux measurement, indirect approaches to flux estimation have
been widely adopted in spite of the large uncertainties associated with them. More
recently Fairall et al (2003) have reported the final version of the bulk flux algorithm that
emerged out of a carefully planned Coupled Ocean-Atmosphere Response Experiment
(COARE) where more than 7216 hours of direct flux measurements were used to validate
the bulk algorithm. They have succeeded in narrowing down the uncertainty from the
then existing 20-30% level to 5% for wind speeds of 0-10 m/s and to 10% for 10-20 m/s
wind speed.
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