[Mitgcm-support] Re: question on modifying code

[mitgcm-support at dev.mitgcm.org]

Theo,

Adding a barotropic body force is fairly straight forward and should
be done in external_forcing_u() and external_forcing_v() which are in
external_forcing.F. 

Adding a new component to vertical velocity is a little more involved.
I didn't realize Samar Khatiwala had done that. If he did, you should
ask him directly (he's at LDEO now) and whether he has the modifications.
There's no template/example in the code of how to do this. The simplest
way to do it is modify the actual W rather than add new terms  (w+W)Tz.
W is set in routine integrate_for_w() which is where you should add
a new component. There will be a lot of issues regards conservation
and interaction with free-surface using this approach so be warned.

In a month or so we will have some confidence in a coordinate change
that is better suited to incorporating barotopic tides. Email us again
later to see if we've finished it then.

Hope this answers your questions,

Alistair.