title: Stretching, alignment, and shear in slowly varying velocity fields.
abstract: We derive criteria that locate intense material stretching and shear in two-dimensional flows with slow time dependence. Our derivation makes use of the near integrability of the equation of variations along trajectories of the slowly varying flow. The criteria yield two diagnostic scalar fields for use in real-time Lagrangian predictions in geophysical flows.
authors.affiliation: Department of Mechanical Engineering, MIT, Cambridge, Massachusetts 02139, USA.
authors.forename: G
authors.initials: G
authors.lastname: Haller
authors.forename: R
authors.initials: R
authors.lastname: Iacono