Tracking dynamic mesoscale structures in the Algerian Basin during operation ELISA (1997-1998) by satellite thermal imagery (NOAA/AVHRR): Potential obstacles to automatic recognition

The amplitude of the variability associated with dynamic mesoscale phenomena is most often greater than that associated with seasonal variability. The role of these phenomena is of the utmost importance as they modify the general circulation of the water masses, and thus, potentially, the circulation in the coastal zone too. But in situ observations at mesoscale require fine spatiotemporal sampling, requiring much effort. Under these conditions, however, NOAA/AVHRR thermal satellite imagery is an extremely efficient tool, as it routinely provides information on a spatial domain over thousands of kilometres, and can generate high-resolution long-term time series. Providing somne precautions are taken, thermal signatures can be interpreted in terms of dynamical structures and associated currents. The use of this satellite imagery within the operation ELISA (1997-1998) provides an opportunity to review the potential limitations to an automatic recognition (detection and tracking) of such mesoscale structures