Inquiry About Nesting My 0.08 Degree Model with GLBb0.08 expt_53.X Data

[hao ming]

Dear Alan,

I hope this message finds you well.

I am currently working on nesting my 0.08-degree model within the GLBb0.08 expt_53.X dataset. Since my model also uses a 0.08-degree grid, I wanted to ask if it is necessary to merge the topography as well.

If I do not merge the topography, what impact could this have on my results? Would it potentially lead to errors in the model's performance?

I appreciate your guidance on this matter.

Best regards,
Minglei Zhong

[Alan Wallcraft]

If you are using a subset of the GLBb0.08 domain and the same identical bathymetry over that subset as expt_53.X, then the only thing you need to do is:

a) Produce the "s" bathymetry which is a subset of GLBb0.08

b) Landmask the edges to produce the bathymetry used by the model

In this case the "best possible" and nested bathmetery are the same, so there is no need to merge topographies.

If your bathymetry is different to GLBb0.08, then you need to merge, so the the bathymetry in the relaxation zone is consistent with the outer model (GLBb0.08).  Otherwise, the relaxation might cause problems.

See https://github.com/HYCOM/HYCOM-examples/wiki/GOMb0.08#1-creation-of-the-grid-and-topography-files

Alan.

[hao ming]

Hi Alan,

Thank you for your previous clarification about using a subset of GLBb0.08 bathymetry. I have a follow-up question about the grid files. If I've successfully extracted a subregion bathymetry file (for example, depth_GOMb0.08_09m11.[ab]) from GLBb0.08 and I want to use  depth_GOMb0.08_09m11.[ab]   as my bathymetry, which grid files should I use for my subregion model?

Should I use:

1. My own regional.grid.[ab] files that I created for my specific subregion domain, or
2. The regional.gmapi_GLBb0.08.[ab] files?

I want to make sure the grid and bathymetry files are properly matched for my nested simulation.

Thank you for your guidance.

[Alan Wallcraft]

The regional.grid file describes your domain

COAPS 51> cat regional.grid.b
  263    'idm   ' = longitudinal array size
  193    'jdm   ' = latitudinal  array size
    0    'mapflg' = map flag (-1=unknown,0=mercator,2=uniform,4=f-plane)
plon:  min,max =       -98.00000      -77.04000
plat:  min,max =        18.09165       31.96065
qlon:  min,max =       -98.04000      -77.08000
qlat:  min,max =        18.05362       31.92670
ulon:  min,max =       -98.04000      -77.08000
ulat:  min,max =        18.09165       31.96065
vlon:  min,max =       -98.00000      -77.04000
vlat:  min,max =        18.05362       31.92670
pang:  min,max =         0.00000        0.00000
pscx:  min,max =      7547.12842     8455.80566
pscy:  min,max =      7547.12842     8455.80566
qscx:  min,max =      7549.91650     8457.63770
qscy:  min,max =      7549.91650     8457.63672
uscx:  min,max =      7547.12842     8455.80566
uscy:  min,max =      7547.12842     8455.80566
vscx:  min,max =      7549.91650     8457.63770
vscy:  min,max =      7549.91650     8457.63672
cori:  min,max =    0.0000451976   0.0000771265
pasp:  min,max =         1.00000        1.00000

The regional.gmapi_GLBb0.08 file describes how to interpolate from GLBb0.08 to your domain.  Since this is an exact subset, it should only have integer values:

COAPS 50> cat regional.gmapi_GLBb0.08.b
GLBb0.08 (4500x3298) to GOMb0.08 (maxinc=3)
xmap:  min,max =   2349.0000   2611.0000
ymap:  min,max =   1735.0000   1927.0000

Follow the wiki instructions for how to create nest files.

Alan