RADAR AND INFRARED MEASUREMENTS OF A COLD EDDY IN THE TYRRHENIAN SEA

Simultaneous airborne measurements of sea surface temperature (SST) by an infrared (IR) radiometer and radar backscatter from a scatteromete r operating at the same C band as on ERS-1, were made over the Tyrrhen ian Sea. The aircraft SST field showed part of the cold and warm eddy system characteristic of the region and compared well with ship-based measurements. The radar backscatter data were examined to investigate whether any dependence on SST could be discerned. It was found that th e radar backscatter data gave a more intermittent view of the eddy and that view appeared to change from day to day. A change in the radar v iew of the eddy could occur due to changing wind fields or atmospheric stability patterns over the thermal front and this hypothesis was dis cussed with regard to two periods with different atmospheric condition s. For two days of very light winds and calm sea conditions the radar signature followed the main thermal gradient features and a positive, significant correlation was obtained between the SST and radar spatial patterns. For a further three days with moderate winds from the north to east quarter, a negative and generally weakening correlation was o btained with SST, with the radar view not identifying the major therma l gradients associated with the eddy.