subroutine sigma_coordinates(first)

Here, the sigma coordinates layer distribution in T-, U- and V-points is calculated.
The layer interfaces for each
layer index have a fixed relative position in the water column,
which may be even equidistant or non-equidistant, see equations
(14) and (16).
The surface and bottom zooming factors
and are read in via the `domain` namelist in `getm.inp`
as `ddu` and `ddl`.
In the first call to the `sigma_coordinates`, the relative interface positions
`dga` are calculated as a one-dimensional vector (in case of
non-equidistant coordinates), and those are then multiplied with
the water depths in all T-, U- and V-points to get the layer thicknesses.
**USES:**

use domain, only: imin,imax,jmin,jmax,kmax,H,HU,HV use domain, only: ga,ddu,ddl use variables_3d, only: kmin,kumin,kvmin,ho,hn,huo,hun,hvo,hvn use variables_3d, only: sseo,ssen,ssuo,ssun,ssvo,ssvn IMPLICIT NONE

logical, intent(in) :: first

Original author(s): Hans Burchard & Karsten Bolding

integer :: i,j,k,rc REALTYPE :: kmaxm1 logical, save :: equiv_sigma=.false. REALTYPE, save, dimension(:), allocatable :: dga

kklingbe 2017-10-02