drifter_in_file solution method types

Question

In the user manual I see 8 options for the solution_method drifter option, but I don't see an explanation of differences between the options. I'm specifically curious about the difference between the Lagrangian particles and the 3D Lagrangian particles.

solution method type of drifter

1 = Drifter with constant elevation

2 = Drifter with constant depth

3 = Drifter with constant density

4 = Lagrangian Particle with constant elevation

5 = Lagrangian Particle with constant depth

6 = Lagrangian Particle with constant density

7 = 3D Lagrangian Particle

8 = 3D Lagrangian Particle with an additional vertical migration component

Answer 1

1) The drifter remains at a constant height relative to your bathymetry datum

2) The drifter remains at a constant depth below the modelled free surface

3) The density adjust its depth to remain at a constant density

4,5,6 are similar 1,2,3 but the drifter moves at the interpolated velocity.  1,2,3 the drag and body shape along with the interpolated velocity are used to calculate the drifter velocity

7) The drifter is fully lagrangian (modelled w velocity is also used)