Create cnleaf_map.nc for 15pfts

[jgipsl]

Only one cnleaf_map.nc is availble at the shared repository in IGCM/SRF/NITROGEN/CN_LEAF. This map contains 13pts. We need it also with 15pfts so it could be used in standard set up such as in LMDZOR_v6.3. See also ticket #474

[aducharne]

Pour le moment, la config par défaut est avec 15 PFT mais STOMATE_READ_CN = n.

[nvuilsce]

The CN map we currently use is named cn_leaf_correct_veget_extend_qua_4D.nc
It has been generated from the file cn_leaf_correct_veget_extend_qua.nc which has been produced by the script genere_ratio_cn_modif_extend_qua.jnl. They are all 3 located under /ccc/work/cont003/drf/p529vui

The script genere_ratio_cn_modif_extend_qua.jnl adjusts the C/N ratio from a ORCHIDEE CNfree simulation in order to get the same GPP in CN fix mode than in CN free mode.
Indeed, one can not get the same behavior in both mode even using a similar CN ratio. GPP tends to be lower in CNfree mode because C allocation can been stopped due to unavaibility of N. This does not happen in CNfix mode.