An exact criterion can be found for partitioning the fluid into regions with different dynamical
properties, from both the points of view of particle dispersion and tracer gradient evolution.
This criterion differs markedly, both in its magnitude and spatial scales, from the Okubo-
Weiss criterion which depends upon the differential geometry of the streamfunction field and
coincides with the eigenvalues of the velocity gradient tensor. The new criterion corresponds
to the eigenvalues of the acceleration gradient tensor, whose spatial distribution depends …