Implicitness parameter for vertical scalar advection and diffusion. Note that this value of thetaS does not necessarily share the same stability properties as the free-surface solver since stability for scalar transport is governed by the horizontal Courant number even when .

- : Fully explicit
- : Crank-Nicolson (Ensures no vertical Courant limitation for advection or diffusion)
- : Fully implicit (same as above but first-order accurate)
- : To guarantee consistency with continuity

2014-08-06