I think there are a couple of things that form the process.
One is doing just what you've done, which is raising it here on meta.
The other, is posting well-written questions on the topics of Earth, Ocean & Atmospheric Modelling, and seeing if the community accepts them, or votes to close them as off-topic. Off-topic is a fairly arbitrary line that gets drawn, to keep the scope well-defined and manageable. It doesn't mean that the whole topic area is out of bounds: just that a particular type of question on a particular topic isn't a good fit on this particular site. So, for example, list questions and recommendation questions do get closed as off-topic, whatever the subject is that they're actually asking about. (they might also be closed as "too broad", or "unclear what is being asked")
Personally, I'd be interested to see these modelling questions, so I support their inclusion within the scope of Earth Science.
My own relationship with the modelling is only as a user of climate impact assessment models, so I couldn't contribute much, but I'll be an interested reader.
It's worth noting, I think, that coding questions can continue to be asked on Stack Overflow, and that there are existing Stack sites for Software Recommendations and for Computational Science. The latter currently has 148 CFD questions, of which 38 are unanswered, so it's not great over there for CFD questions, but not too awful either.