Confusing coupling order - oasis send

[jcastill]

Context

In the file sbccp.F90, each field that can be exchanged via coupling has its own index. The order in which the fields are received via coupling is the same as fields index, but this is not true for the sent fields, as the order is hard coded in the routine sbc_cpl_snd. This can cause some confusion for users, which can easily create a deadlock condition, in particular in cases where several models are coupled to NEMO.

Analysis

The index order of the oasis sent fields should be the same as the order in which the fields are coupled to increase clarity.

Recommendation

The index order and the coupling order should be rearranged so that fields being sent to the same model component are grouped together to avoid potential deadlocks and to increase clarity and usability. The proposed order is: atmosphere, atmosphere ice, waves, wave ice. The addition of new coupling fields should take this order into account.