Large-scale oceanic features detected by airborne SAR in the Mediterranean sea

Abstract

During the MAC-Europe Campaign in June/July, 1991, the NASA JPL synthetic aperture radar (SAR) carrying a polarimetric 3-frequency SAR operating at 440 MHz (P-Band), 1.25 GHz (L-Band) and 5.30 GHz (C-Band) flew several missions over the Gulf of Genoa and the Strait of Messina. On June 22, 1991, SAR images were taken over the Gulf of Genoa showing an anti-cyclonic eddy south of Genoa having a diameter of approx. 15 km. Model calculations carried out by V. Casulli, (University of Trento) and G. Mansella (ENEA, La Spezia) show that this eddy is generated by the modification of the steady cyclonic circulation caused by wind forcing and the interaction with the coastline and the bathymetry. This model result is also substantiated by AVHRR images. On June 28, 1991, SAR images were taken over the Strait of Messina showing a strong non-linear interval wave train south of the Strait of Messina. This wave train was imaged several times. By correlating successive SAR images the propagation speed of the internal waves is determined. During the passes over the Strait of Messina the JPL SAR was operated in an interferometric SAR-mode by using two antennas. Surface current velocities as well as correlation times are derived from these interferometric data (R. Carande, JPL). The airborne SAR images are compared with radar images acquired by the C-band SAR aboard the First European Remote Sensing Satellite ERS-1 over the Strait of Messina. Several of these ERS-1 SAR images display surface manifestations of internal waves. They are interpreted in terms of theoretical models on the generation of internal waves in the Strait. >