[MITgcm-support] [EXTERNAL] Problems with the EXF package and binary input files

Thu Feb 9 13:01:28 EST 2023

just a wild guess, for using the regridded dataset, did you unset the following flag in EXF_OPTIONS.h during compilation:

C-  Use spatial interpolation to interpolate
C   forcing files from input grid to model grid.
#undef USE_EXF_INTERPOLATION

or alternatively, did you set following flag to 0 in data.exf during runtime

C   {inputField}_interpMethod :: interpolation method: =0 : no interpolation ;
C                             :: =1,11,21 : bilinear ; =2,12,22 : bicubic ;
C                             :: =1,2 for tracer ; =11,12 for U ; =21,22 for V.

D.

On Feb 9, 2023, at 8:30 AM, Dani Jones <dcjones.work at gmail.com> wrote:

Hi Oliver,

You've found the error! Well spotted. By changing `field_lat_inc = 0.25` to `field_lat_inc = 249*0.25` throughout, where Ny=249 is the number of latitude points in my ERA5 subset, I was able to get sensible-looking EXF diagnostics output.

I am still a bit surprised that using a regridded dataset didn't fix my issue, though. I was thinking that I could regrid the ERA5 data onto the model grid, comment out the interpolation-related grid parameters in `data.exf`, and use the default values. Oddly, this didn't work. I might do some more tests on this later, but for now I'm happy to have something that runs.

Thanks again!

Best wishes,
Dan(i)

On Thu, Feb 9, 2023 at 3:34 PM Oliver Jahn <jahn at mit.edu<mailto:jahn at mit.edu>> wrote:
Hi Dan,

I noticed one thing in your data.exf: there is only 1 value for vwind_lat_inc which is an array.  You have to provide vwind_nlat-1 values.  (This is needed for things like Gaussian grids but definitely could use more coverage in the docs!)

Oliver

On 2023-02-09 09:16, Dani Jones wrote:
> Hello MITgcm-support listers,
>
> I am having trouble with the EXF package while trying to force a
> regional model configuration using external fields derived from ERA5.
> The diagnostics output from EXF shows horizontal stripes or distorted
> results.
>
> To set up my configuration, I followed these steps:
>
>   * Downloaded a subset of ERA5 using the cdsapi package
>   * Regridded the data onto my model grid using the xESMF package
>   * Ran MITgcm for a few timesteps and checked the EXF diagnostics output
>
> I have conducted various checks and tried different approaches to
> resolve the issue, including:
>
>   * Examined the contents of the ERA5 data
>   * Examined the binary files for any problems
>   * Tried "on the fly" interpolation with EXF and repeatedly checked the
>     data.exf parameters
>   * Checked the precision and endian-ness throughout the entire process
>   * Created binary files using Matlab and Python
>   * Updated to the latest version of MITgcm and recompiled with the
>     -D_BYTESWAPIO flag
>   * Tried every permutation of the dimensions for the binary files
>
> Despite these efforts, the binary files appear to be fine, and it seems
> that MITgcm/EXF is not reading them as expected. For further information
> and details, I have documented this issue on GitHub with plots from the
> diagnostics package and links to relevant files:
>
> https://github.com/so-wise/so-wise-gyre/issues/34<https://urldefense.us/v3/__https://github.com/so-wise/so-wise-gyre/issues/34__;!!PvBDto6Hs4WbVuu7!cM_FgSyA7SS_rYeOdAm6pNa9WR4JGr_Kbv0SGzwI5YCzNrN0mLBfK4eskiRcUE0mNcSjKDrD3xk$>
> <https://github.com/so-wise/so-wise-gyre/issues/34<https://urldefense.us/v3/__https://github.com/so-wise/so-wise-gyre/issues/34__;!!PvBDto6Hs4WbVuu7!cM_FgSyA7SS_rYeOdAm6pNa9WR4JGr_Kbv0SGzwI5YCzNrN0mLBfK4eskiRcUE0mNcSjKDrD3xk$>>
>
> Thanks in advance for any assistance, guidance, or suggestions that you
> can provide.
>
> Best regards,
> Dan(i)
>
> --
> *Dr Dan(i) Jones* • Physical Oceanographer
> Polar Oceans Team <https://www.bas.ac.uk/team/science-teams/oceans/<https://urldefense.us/v3/__https://www.bas.ac.uk/team/science-teams/oceans/__;!!PvBDto6Hs4WbVuu7!cM_FgSyA7SS_rYeOdAm6pNa9WR4JGr_Kbv0SGzwI5YCzNrN0mLBfK4eskiRcUE0mNcSjp-0_INE$>>•
> BAS AI Lab <https://www.bas.ac.uk/project/ai<https://urldefense.us/v3/__https://www.bas.ac.uk/project/ai__;!!PvBDto6Hs4WbVuu7!cM_FgSyA7SS_rYeOdAm6pNa9WR4JGr_Kbv0SGzwI5YCzNrN0mLBfK4eskiRcUE0mNcSjjQBycJY$>> • British Antarctic Survey
> <https://www.bas.ac.uk/<https://urldefense.us/v3/__https://www.bas.ac.uk/__;!!PvBDto6Hs4WbVuu7!cM_FgSyA7SS_rYeOdAm6pNa9WR4JGr_Kbv0SGzwI5YCzNrN0mLBfK4eskiRcUE0mNcSjqsRZZC4$>>
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