[MITgcm-support] 2D model - Varying cell width (delY)

[Pascal Bourgault]

Hi!

I am currently working on a 2D model (X and Z) of an estuary with the 
MITgcm. My goal was to simplified the problem by ignoring lateral 
advection, horizontal eddies and lateral variation of the bathymetry, 
while keeping the vertical shear- and bathymetry-induced mixing. So I 
have a 1 m Δz and a telescopic Δx, going from 65 m to 20 m in the center 
and back to ~ 120 m at the mouth of the estuary, where I use OBCS to 
prescribe T, S and U.

One problem we are currently having is that Δy is constant. There is a 
single y row of 50 m (a number chosen so that the Δx/Δy ratio stays 
reasonable throughout the regions of interest). That means that only the 
bathymetry makes the cross-section area vary along the estuary. In order 
to get something a bit more realistic, I was wondering if there was a 
way to have a varying Δy in the model? AFAIU, that means having dyF a 
function of x (and not only of y). As long as I stay with 1 row of 
cells, it would be geometrically sane, but is it doable in the MItgcm?

I am ready to get my hands dirty and to dig a bit in the code, but I 
would like to have the opinion of experts. Where should I modify the 
source? I see that "/model/src/ini_cartesian_grid.F" is a good start, 
but I expect it to be a bit more difficult than that?

I am currently trying the solution of having a few rows in y and putting 
walls to simulate the narrowing of the channel. However, that adds a lot 
of computation and creates "singularities" since the variation of Δy 
isn't smooth at all.


Thanks!

--
Pascal Bourgault