Create subdirectory Ocean_skin in libf. For now, Ocean_skin is under
control of git, not subversion.
Add variable eps_w to common YOMCST.
For now, continue to read ocean skin parameters from a namelist in
config_ocean_skin.
The parameterisation is called from procedure surf_ocean.
Add two prognostic variables for the parameterisation: dt_ns and
ds_ns. Add eight diagnostic variables: t_int, s_int, dter, dser, tkt,
tks, rf, taur. The ten variables are only defined on ocean surface,
elsewhere they are set to nf90_fill_real. In pbl_surface, we can
initialize the eight diagnostic variables to nf90_fill_real before the
loop on sub-surfaces, but we need to keep the old values of dt_ns and
ds_ns as input of the parameterisation so we set dt_ns and ds_ns to
nf90_fill_real after the call to surf_ocean. Define ten corresponding
compressed variables in pbl_surface. Define ten corresponding NetCDF
output variables in phys_output_ctrlout_mod.
In procedure pbl_surface_newfrac, for an appearing ocean sub-surface,
dt_ns and ds_ns are set to 0. In phyetat0, also set initial dt_ns and
ds_ns to 0 if they are not in start file.
In procedure surf_ocean, for now, we use a constant specific latent
heat of vaporization, as elsewhere in LMDZ, and a constant bulk
salinity.
