== Catering for MEDUSA coupling via OASIS3-MCT ==


'''Background'''

We need to cater for MEDUSA coupling at NEMO vn3.6 via the existing NEMO OASIS3-MCT interface and the Met Office UM code. 

This work is initially primarily for the purposes of the UKESM project, however ultimately it is considered that the MEDUSA coupling interface would become a generally available option to any configuration which chooses to employ it. 


'''Developmemt'''

The MEDUSA code itself is held in a development branch, created and maintained at NOC named, at time of writing, [log:branches/NERC/dev_r5518_NOC_MEDUSA_Stable dev_r5518_NOC_MEDUSA_Stable]
 
This code potentially provides output fields to a coupler and receives input fields from a coupler to allow it to couple with an atmosphere model featuring dust and vegetation schemes. 

Currently the specific coupling fields are expected to be:

* Output:
   * CO2 Flux (MEDUSA field f_co2flux2d)
   * DMS  (MEDUSA field dms_surf2d)

* Input:
   * CO2 partial pressure (MEDUSA field f_pco2a. This is expected to come from the atmosphere and in the case of the UM specifically from the "TRIFFID" scheme)
   * Dust (MEDUSA field dust.  This is expected to come from the atmosphere and in the case of the UM specifically from some special code which is as yet undeveloped!)