Basin- to mesoscale surface circulation of the Western Mediterranean manifested by satellite-derived data products

Abstract

In this article, there is an overview of the potential of different (mostly altimetry-derived) products for manifesting features of basin- and mesoscale circulation of the Western Mediterranean Basin. In terms of detection of mesoscale eddies and larger gyres, the comparison was performed between eddy statistics extracted directly from fields of sea surface temperature (SST), on the one hand, and reconstructed from different scalar and vector altimetry-derived fields, on the other hand. Among the products being analysed, there are fields of (i) sea level anomaly (SLA), (ii) geostrophic currents, and (iii) finite size Lyapunov exponents (FSLE). Comparison of the eddy statistics provided by such different data sources revealed that altimetry-based techniques tended to overestimate the number of big cyclones and thus failed to reproduce cyclonic/anticyclonic eddy asymmetry which was shown by fields of SST. Defining the spatial scale of eddies via altimetry-based techniques seemed particularly problematic. FSLE product analysed in the study showed significant disagreements with vortical structures observed in fields of SST both in terms of the spatial scale and the sign of rotation. In order to scrutinize basin-scale features of surface circulation in the region of interest, fields of (i) geostrophic currents, (ii) total currents reconstructed by the GlobCurrent project, and (iii) surface currents provided by the reanalysis technique were analysed. As a result of the comparison performed, a conclusion was made on the complementarity of the datasets analysed.