finding neighboring grid

[yfang]

Hi, I'm trying to find out the neighbors of a structured grid in the land component. Where can I start in the code? Thanks!

 

[erik]

This is actually a big ask, since we've intentionally made the grid cell neighbors irrelevant. That way it doesn't matter what order you process the grid cells in, and doesn't require communicating halo information between neighboring grid cells. So it makes CTSM "embarrassingly parallel" and very fast. But, it also means that neighbor grid cells are scattered around and getting information on the neighboring gridcells is problematic.

What is the science question that you need to know the neighboring grid cells?

We did have some discussion of this issue in FATES on github in the context of seed dispersal here:

Seed dispersal in FATES · Issue #471 · NGEET/fates

Is it possible to add seed dispersal in FATES? At the CTSM 2019 tutorial, @rosiealice @jkshuman @rgknox @ekluzek, me and others started discussing options for integrating dispersal mechanisms in FA...

github.com

 

[yfang]

@erik Thanks for pointing me to the discussion. I'm interested in flux exchange between grid cells. I noticed you touched on it in the discussion.

 

[erik]

So exchange of soil moisture and heat between grid cells? Unfortunately CTSM would be horrible for that, you'd likely be better off looking at a different model. Something like exchange of seeds on a yearly basis would be inefficient, but if it's done seldom enough it would be OK. But, if you are exchanging fluxes on each time-step that would make it perform really horribly. I suppose if you have a small grid and aren't too concerned with performance you could get something to work, but it won't be optimal. So as long as you know that from the start.