Performance of gridded and along-track altimetry products in eddy manifestation in the Western Mediterranean

In the present work, we assess the performance of different sea level anomaly (SLA) products in manifesting mesoscale eddies of the Western Mediterranean. As ‘ground truth’ in this study we use eddy manifestations found in sea surface temperature (SST) fields of the region of interest. Co-location of eddies found in thermal imagery with closed contours of the fields of SLA showed that only anticyclonic eddies exceeding approx. 70 km in diameter can be more or less sustainably manifested in the fields of SLA and its derivatives. Detection of cyclonic eddies, presumably due to their small spatial and temporal scales and non-geostrophic nature, is problematic. A preliminary analysis of the along-track SLA data seemed to support the conclusions made for the gridded SLA products. Application of a vector geometry approach to eddy detection, in its turn, seems to lead to an excess of large cyclonic eddies and thus biasing resulting mesoscale eddy statistics.