Develop simple test case enabling east west AND south north cyclic boundaries

[clevy]

Context

In order to have an appropriate test case for the AGRIF_LIM3 development (2016 workplan AGRIF-2 Shared action), a few developments have been made in order to be able to set up a simple rectangular box on f-plane with flat bottom. Boundary conditions are cyclic east-west (exisiting with jperio=1 in &namcfg namelist) and north-south (developped with jperio=7).

Implementation

The test case has been developped for a new SASBIPER configuration where ocean is inactive (using SAS and surface ocean variables = 0.). Ice is initialised using a file (initice.nc) where all fields are constant except sea-ice thickness initialised with a gaussian bump constant in latitude.
Ice is only active through ice velocities initialised analytically in the namelist.
It will be used with and without AGRIF-LIM3 to test the AGRIF-LIM3 development.
This ticket only describes the changes in the code.
For now changes are implemented in the AGRIF-LIM3 development branch: ​http://forge.ipsl.jussieu.fr/nemo/svn/branches/2016/dev_v3_6_STABLE_r6506_AGRIF_LIM3

List of modified routines and namelists:

• OPA_SRC/DOM/domcfg.F90 :

add a new option jperio=7 for global lateral boudaries:

IF( jperio == 7 ) WRITE(numout,*) ' jperio= 7, cyclic east-west and north-south'

• OPA_SRC/DOM/domzgr.F90:

Add definition of mbathy for jperio=7

• OPA_SRC/LBC/lib_mpp.F90

Add the cyclic east-west and north-south boundaries option when MPP active (= with cpp key key_mpp_mpi). Important: as for east west cyclic, it ONLY works when using one process (mpirun -n 1 ./opa and nbondi=nbondj=2).
No implementation for key_bdy active either.

• OPA_SRC/LBC/mppini.F90

Add jperio=7 option

• SAS_SRC/sbcssm.F90

Beware it is in SAS_SRC and not in OPA_SRC/SBC!
Added logical variable l_sasread in &namsc_sas namelist (=.TRUE. by default in namelist_ref) to allow using SAS with or without reading a file to initialise ocean surface fields.
If l_sasread=.TRUE. The model reads in a file the fields defined in &namsbc_sas namelist
if l_sasread=.FALSE. fields are initialised in sbcssm.F90:

ELSE

sst_m(:,:) = 0.
sss_m(:,:) = 0.
ssu_m(:,:) = 0.
ssv_m(:,:) = 0.
ssh_m(:,:) = 0.

• SHARED/namelist_ref:

Add l_sasread=.TRUE. in &namsbc_sas namelist

A simple python script has been build to create the initial fields for sea-ice (attached to this ticket for now)

Done in development branch at revision 6861 : https://forge.ipsl.jussieu.fr/nemo/changeset/6861/branches/2016/dev_v3_6_STABLE_r6506_AGRIF_LIM3/NEMOGCM