qprecond: 0,1, or 2

Type of preconditioner to use for the nonhydrostatic pressure solver. For a typical environmental flow with an aspect ratio of $\mathcal{O}\left(10^2\right)$:

0

No preconditioner - 1000s of iterations to converge

1

Diagonal preconditioner - 100s of iterations to converge

2

Block-diagonal preconditioner - 10s of iterations to converge.

There is no significant difference among the preconditioners when the aspect ratio is roughly 1.