Calculating Lagrangian trajectories using time-dependent velocity fields

The authors report on the development of an efficient and accurate tool for computing Lagrangian trajectories using time-varying velocities. By linear ly interpolating the velocities both in space and time one can obtain analy tical expressions for the trajectory inside each model grid box. In combina tion with a numerical determination of the transit times through each grid box, these expressions allow for the implementation of expedient algorithms for offline analyses of large datasets resulting from general circulation models. The authors demonstrate the efficacy of this approach on a time-var ying two-dimensional model gyre.