Turn off vertical tracer flux?

[nwoods]

I'm trying to model a quasi-passive tracer that is constrained to sit at a fixed depth, but is advected by the horizontal flow (analogous to an isobaric float). Has anyone tried to do something like this before? I suppose it is possible to eliminate vertical advection somehow, (perhaps commenting out the vertical advection and diffusion in "step3d_t"?), but am not sure. Any advice would be greatly appreciated!

[kate]

If you simply turn off the vertical advection term, the tracer will ride along constant-s contours, not constant-z contours. To do what you want, you would need to add a 'behavior' of seeking a fixed depth.

[arango]

Also notice that in ROMS it is possible to set horizontal and vertical diffusivity coefficients to zero. The vertical fluxes of tracers (surface and bottom) can be also set to zero. However, you will have vertical fluxes of tracer in the interior for upwelling and downwelling situations. There is not a specific switch to turn the vertical advection of tracer.

The Lagrangian drifters have an option for isobaric floats.