Data from: Cyclone-anticyclone asymmetry of eddy detection on gridded altimetry product in the Mediterranean Sea

We perform an Observing System Simulation Experiment that simulates the
satellite sampling and the mapping procedure on the sea surface of the
high-resolution model CROCO-MED60v40, to investigate the reliability and
the accuracy of the eddy detection. The main result of this study is a
strong cyclone-anticyclone asymmetry of the eddy detection on the
altimetry products AVISO/CMEMS in the Mediterranean Sea. Large-scale
cyclones having a characteristic radius larger than the local deformation
radius are much less reliable than large-scale anticyclones. We estimate
that less than 60% of these cyclones detected on gridded altimetry product
are reliable, while more than 85% of mesoscale anticyclones are reliable.
Besides, both the barycenter and the size of these mesoscale anticyclones
are relatively accurate. This asymmetry comes from the difference of
stability between cyclonic and anticyclonic eddies. Large mesoscale
cyclones often split into smaller sub-mesoscale structures having a rapid
dynamical evolution. The numerical model CROCO-MED60v40 shows that this
complex dynamic is too fast and too small to be accurately captured by the
gridded altimetry products. The spatio-temporal interpolation smoothes out
this sub-mesoscale dynamics and tends to generate an excessive number of
unrealistic mesoscale cyclones in comparison with the reference field. On
the other hand, large mesoscale anticyclones, which are more robust and
which evolve more slowly, can be accurately tracked by standard altimetry
products. We also confirm that the AVISO/CMEMS products induce a bias on
the eddy intensity. The azimuthal geostrophic velocities are always
underestimated for large mesoscale anticyclones.