THE SAR MEASUREMENT OF OCEAN WAVES:WAVE SESSION WHITEPAPER

摘要

Remote sensing techniques enable the measurement ofrnocean wave fields with both high resolution and largerncoverage. As the acquisition of active radar data isrnindependent of daylight and cloud conditions, theserndata are therefore believed to be most suited forrnoperational use at weather centers and governmentalrnagencies, as well as for many ongoing scientificrninvestigations. In the present overview paper therndetermination of sea state parameters from radarrnimages together with some results from the operationalrnuse at weather centers are given.rnSynthetic aperture radar (SAR) yields high resolutionrntwo dimensional images of the radar backscatterrnproperties of the sea surface and can thus be used tornmeasure wind fields and sea state from space.rnThe determination of ocean wave spectra from SARrnimage spectra is sensitive to various imaging effectsrndue to sea surface features, spatial variation of windrnspeed, rain, current and motion of the sea surface.rnThus, measuring ocean wave parameters is related tornmost of the other measurements of marine parametersrndescribed in this volume.rnIn this paper an overview of the SAR satelliternmissions is given, as well as a description of the basicrntechniques to measure ocean waves by SAR andrnvalidation against wave model results and other spacernborne and in situ measurements.rnThe full two dimensional SAR image spectrumrnprovides information on the directional ocean wavernspectrum. This can be used to determine expectationrnvalues of, e.g. , significant wave height, mean wavelength and direction in order to improve the wavernmodel prediction. In addition information can berngathered from the radar images directly such asrnindividual wave height, crest length and groupiness ofrnthe ocean waves. Thus, the distribution of maximumrnwave height can be investigated globally, or wavernrefraction and diffraction in coastal areas can bernstudied in detail.rnIn the following an overview of ocean wavernmeasurements from space are given, the papersrnpresented in the wave session are put into the generalrncontext and applications for weather prediction, shiprnrouting, oil and shipbuilding industry and shiprnclassifying societies are discussed.rnA general overview on theory and measurement ofrndirectional wave spectra, including a special chapter onrnremote sensing of directional ocean wave spectrarntogether with an extensive literature list is given in thernCOST Book (2004).