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Infrared (IR) remote sensing from satellites is a well-proven technique for measuring sea surface temperature (SST) and for detecting and monitoring oceanographic features which have strong thermal contrast. Unfortunately, cloud cover often limits the continuity of the datasets and therefore their usefulness. There is some evidence that radar backscatter can be modified by sea surface temperature structure which raises the possibility that sensors such as synthetic aperture radar, scatterometers and altimeters could provide an all-weather complement to those operating in the IR. As a background, the results of a project which used coincident airborne radar and IR measurements of an eddy system in the Tyrrhenian Sea during October 1989 are briefly described. During a 5-day period, variations in radar backscatter of several dB occurred in a region where SST varied by 2 - 3 degree(s)C. The correlation between normalized radar cross section, sigma naught ((sigma) 0 or sigma-0) and SST appeared to depend on the ambient wind. Unfortunately, no satellite radar data were available during the experiment, since Geosat had just failed and ERS-1 was not due for launch until 1991. Building on this work, a study has commenced in which preliminary analyses of ERS-1 altimeter data, from tracks which repeat every 3 days, have been conducted for a section of the Gulf Stream after it has separated from the US coast. The along track variation of sigma naught has been compared with contemporaneous NOAA AVHRR-2 imagery and the relationship between SST structure and sigma naught for individual passes is discussed in terms of environmental parameters such as the local wind field and ocean currents. The possibility of the interaction of environmental parameters such as waves and currents are explored and some evidence for both wave enhancement and attenuation at the north wall of the Gulf Stream is illustrated. Tentative explanations for relationships observed by the various analysis techniques are advanced and further planned work discussed.
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