# Looking for the exact ORCA025.L75 static/grid files consistent with ORAS5

**URL:** <https://nemo-ocean.discourse.group/t/looking-for-the-exact-orca025-l75-static-grid-files-consistent-with-oras5/1002>\
**Category:** Global\
**Tags:** orca\
**Created:** [13 March 2026 20:23 UTC](https://nemo-ocean.discourse.group/t/looking-for-the-exact-orca025-l75-static-grid-files-consistent-with-oras5/1002 "2026-03-13T20:23:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![toto](https://avatars.discourse-cdn.com/v4/letter/t/9f8e36/32.png) [@toto](https://nemo-ocean.discourse.group/u/toto)\
**Post date:** [13 March 2026 20:23 UTC](https://nemo-ocean.discourse.group/t/looking-for-the-exact-orca025-l75-static-grid-files-consistent-with-oras5/1002/1 "2026-03-13T20:23:55Z")

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Hi everyone! I am trying to compute AMOC-related diagnostics from ORAS5 on the native 0.25° grid, and I am currently stuck on identifying the correct static/grid files that should be used together with it.

From the ECMWF documentation and the ORAP5/ORAS5 papers, my understanding is that ORAS5 uses NEMO v3.4.1 and the same spatial configuration as ORAP5, namely ORCA025.L75, often referred to as the DRAKKAR reference configuration. However after spending quite a bit of time going through the documentation, papers, repositories, and related resources, I still have not managed to determine the exact provenance of the static files that are actually consistent with ORAS5.

What I am trying to locate are the corresponding domain or mesh files, such as the equivalents of `domain_cfg.nc`, `mesh_mask.nc`, bathymetry, basin masks, and the grid metrics needed for transport calculations like `e1v`, `e3v`, `bottom_level`, and related fields.

I also found the ICDC ORAS5 pages, which seem very relevant, but at the moment the THREDDS/OpenDAP links are repeatedly returning 504 timeout errors on my side, so I have not been able to verify the files directly.

Any precise pointer or practical advice from people who have already computed transports, MOC, or AMOC from ORAS5 would be extremely helpful.

Thank you!!!

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**Author:** ![cpelletier](https://avatars.discourse-cdn.com/v4/letter/c/46a35a/32.png) [@cpelletier](https://nemo-ocean.discourse.group/u/cpelletier)\
**Post date:** [16 March 2026 10:21 UTC](https://nemo-ocean.discourse.group/t/looking-for-the-exact-orca025-l75-static-grid-files-consistent-with-oras5/1002/2 "2026-03-16T10:21:24Z")

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Hi, your understanding is correct!

The mesh\_mask file used for ORAS5 is available [here](https://icdc.cen.uni-hamburg.de/thredds/catalog/ftpthredds/EASYInit/oras5/ORCA025/mesh/catalog.html).

ORAS5 uses partial cells at the bottom, meaning the thicknesses of the lowest wet cell depend on location/bathymetry. The fields `e3t_ps` and `e3w_ps` give you the thicknesses of the lowest wet cells for grid type T and W. Not sure how to consistently derive the lowest `e3u`/`e3v` values from that, though… the minimum (or maybe the average?) of the two adjacent T cells should be good enough.

Hope this helps