The new versions of the Mesoscale Eddy Trajectories Atlas, META3.1exp DT allsat and twosat, provide new parameters for eddy detection and an improved tracking scheme.

The META3.1exp DT allsat (DOI : 10.24400/527896/a01-2021.001>) and twosat (DOI : 10.24400/527896/a01-2021.002) versions differ from the historical META2.0 product by 4 evolutions: 

- The eddy detection is made on Absolute Dynamic Topography maps instead of Sea Level Anomaly maps, for a better representation of mesoscale structure over Mean Dynamic Topography specific patterns 

- The filter applied on the input maps is an 2D Lanczos filter with a 700 km half-power cutoff wavelength, to better take into account the spatial scales of the Mean Dynamic Topography. The filter used in META2.0 had a 1000 km half-power cutoff wavelength. 

- The detection algorithm of META3.1exp is the Py-Eddy-Tracker, freely available on a GNU license at https://github.com/AntSimi/py-eddy-tracker, written in the Python language and associated with a large documentation (https://py-eddy-tracker.readthedocs.io/en/v3.3.1/). The main changes are the amplitude threshold (0.4 cm), the unique extremum within an eddy, and the availability of the eddy’s contours. 

- The tracking scheme is now based on the contour’s overlap, with a maximum of 4 consecutive virtual eddies. 

Each change was evaluated with a similarity coefficient, comparing individual eddies in intermediate datasets, to ensure a continuity between META2.0 and META3.1exp.