News

The new version of the Mesoscale Eddy Trajectories Atlas META3.2exp NRT is available on AVISO+.

It is an experimental product and replaces the version 3.0exp NRT.

The differences between versions 3.0 and 3.2 are the following:

• Pre - processing step : the NRT Absolute Dynamic Topography maps are filtered with an order 1 (previously order 3) 2D Lanczos filter with a half-power cutoff wavelength of 700 km (previously 500 km). These changes provide a better representation of the major currents gradients and the 1rst order filtering works better for pixels close to the land.
• Detection sheme : the 55% threshold for the shape error test is increased to 70% to better take into account the eddy's deformation before and after interactions.
• Tracking scheme : the association of eddies in trajectories is made when the contours of the eddies overlap from one day to another. Previously, the association was made by searching within a restricted area the closest eddy. The overlap method ensures a geographic coherence and prevents associations of independant trajectories. Moreover, the number of consecutive virtual observations - virtual observations are added when an association is made not the day after, but several days after the initial detection - is increased from 3 to 4.
• Contour sampling : the contours coordinates are now stored on 20 points based on the Visvalingam algorithm to preserve the shape of the contour. Previously, contours coordinates where stored on 50 points uniformely spaced, resulting in larger files.
• Time format : now the time is stored in float, previously it was in integer.

Note that both the change for the time format and the change in the the contour sampling may impact your code.

Moreover, the cumulated changes imply that there is no continuity between the previous 3.0exp and the 3.2exp two versions.

All information in the product page.

ACCESS:

The new files will be available on FTP on the same folder as for version 3.0expNRT

Any questions/remarks can be addressed to aviso(at)altimetry.fr