Plot geo-map for MITgcm grid

Q&A
1

Hi, everyone

I try to plot the geographic map for the MITgcm model which has complex grid difficult to project on map.

More information could be found here:
https://medium.com/pangeo/petabytes-of-ocean-data-part-1-nasa-ecco-data-portal-81e3c5e077be

The model grid itself is a complex lat-lon-cap (LLC) curvilinear grid which is difficult to visualize in a regular map projections.

I just download the data and its’ structure seems:

image
image993×206 19 KB

You can see that the data have latitude and longitude as the 2D variables instead of 1D dimensions.

The data could be shown using JX projection:

gmt begin Aghulhas png
	gmt set MAP_ANNOT_OBLIQUE 0
	gmt grd2cpt myfile3.nc?Theta -Cjet -Z
	gmt grdimage myfile3.nc?Theta -I+a90  -R1000/2000/2500/3500 -JX15/13c -B100 
	gmt colorbar -DJRM+o1.c/0+mc -I0.3 -Bx2+lTheta -By+ldegree
gmt end show

Aghulhas
Aghulhas891×654 250 KB

So, is it possible to plot geo-map for this kind of data?
Dose anyone have suggestions for this question?

Thanks

Lei

2

I crop a small file (LLC4320). Anyone who interests this question could find the data here: https://www.jianguoyun.com/p/DYpRAn0Q2PCQBxijq9AEIAA

Please trying this code:

gmt begin Aghulhas2 png
	gmt set MAP_ANNOT_OBLIQUE 0
	gmt grd2cpt myfile_sa.nc?Theta -Cjet -Z
	gmt grdimage myfile_sa.nc?Theta -I+a90  -R2000/4500/5000/6500 -JX7/5c -B500 
	gmt colorbar -DJRM+o0.5c/0+mc  -Bx5+lTheta -By+ldegree
gmt end show
3

This is a recurrent question. My answer to it is: use the Julia package “RemoteS” that has a function to solve exactly these cases.

4

Thanks Joaquim.
I installed the Julia GMT and RemoteS. Good tools. I find you shared one good example:https://www.generic-mapping-tools.org/RemoteS.jl/dev/gallery/Aqua_sst/remotes_L2_SST/

It is similar to the LLC data structure. I will give a try based on this example.

Lei

5

GMTjl_tmp
GMTjl_tmp1795×1537 425 KB

G = grid_at_sensor("./myfile5.nc", "Theta",region=(10,40,-50,-10), inc=0.03);
imshow(G, proj=:guess, coast=true, dpi=200)

Really cool tools. Only two lines.

But I have another simple question: where or how dose Julia GMT save the figure?

Another suggestion:
The RemoteS seems only know the variable name as latitude or longitude, but does not check the long name or standard name. Just like the data I shared, the variable name: XC YC stands for latitude and longitude and they are presented in the long name or standard name. So it fails to use it directly.

6

Use figname=newname.png option

See the function online help. I must have accounted for those cases. Otherwise please open an issue.

Sorry for these short answers but I’m somewhere in an island with no computer with me.

7

Thanks.
I missed the online documents. It was already mentioned and fixed my question.
Now, it is very nice.

G = grid_at_sensor("./myfile4.nc", "Theta",region=(0,50,-50,-10),xarray="XC", yarray="YC", inc=0.03);