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