Escape probability and mean residence time in random flows with unsteady drift

We investigate fluid transport in random velocity fields with unsteady drif t. First, we propose to quantify fluid transport between Bow regimes of dif ferent characteristic motion, by escape probability and mean residence time . We then develop numerical algorithms to solve for escape probability and mean residence time, which are described by backward Fokker-Planck type par tial differential equations. A few computational issues are also discussed. Finally, we apply these ideas and numerical algorithms to a tidal Bow mode l.