Small Scale Processes in the South Atlantic Observed in Synergy of Atsr and Sar Data during the Tandem Mission

During the ERS1-2 Tandem Mission in 1995-6, the synthetic aperture radar (SAR) swath on one satellite overlapped the along-track scanning radiometer (ATSR) swath on the other with a 30 min interval, at latitudes greater than 50°. A number of matching pairs of SAR and partially cloud-free ATSR images were found in the ERS archive covering the South Patagonian Shelf, the Drake Passage and the Antarctic Peninsula. The SAR.PRI image data were reduced to 200m pixels by rms averaging, and the ATSR .GBT and .GSST 1km image products were warped onto the same 200m grid as the corresponding SAR scene. Following image enhancement, requiring a de-trending of the SAR image to remove the response of normalised radar cross section (NRCS) to the viewing geometry, visual comparison was made between the two types of data. While no strong mesoscale dynamical features were encountered, a number of small scale thermal signatures were detected, close to the coast or near the ice edge. A variety of signature types were found in the corresponding SAR scenes, which closely matched the location of the thermal signatures, including linear NRCS features, step changes of NRCS and changes in NRCS texture. In this remote region, for which there is little systematic oceanographic knowledge, the combination of the radar and thermal signatures facilitates the interpretation of the data, and demonstrates the usefulness of the synergetic approach for studying coastal ocean dynamics. Coupled with previous analyses of north-east Atlantic data, these matched image pairs point to the potential in future for oceanographic applications of synergetic analyses of combined simultaneous AATSR, ASAR (ScanSAR mode) and MERIS data from Envisat.