quadruple check if KiD's velocity field derivation does not require correction

[slayoo]

In kid_a_setup/src/test_cases_2d.f90:975 the stream function is defined as:

PHI(i,k)=PHI(i,k)_AMPL_rho(k)

what implies that the density is later being numerically differentiated to obtain momenta, while it should not be as the in the relationship betwen momenta and stream function the density is not under the derivative:

rho * u = d phi / dz