# ACCESS-coupled N48 issue #1: change topography, bathymetry and land-mask **URL:** \ **Category:** Earth System\ **Created:** [21 March 2023 00:32 UTC](https://forum.access-hive.org.au/t/access-coupled-n48-issue-1-change-topography-bathymetry-and-land-mask/574 "2023-03-21T00:32:05Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Dietmar\_Dommenget](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/dietmar_dommenget/32/494_2.png) [@Dietmar\_Dommenget](https://forum.access-hive.org.au/u/Dietmar_Dommenget)\ **Post date:** [21 March 2023 00:32 UTC](https://forum.access-hive.org.au/t/access-coupled-n48-issue-1-change-topography-bathymetry-and-land-mask/574/1 "2023-03-21T00:32:05Z")
Dear ACCESS-NRI team, How can we change topography, bathymetry and land-mask in the ACCESS-coupled N48? As a starting point I would suggest we just change a dummy test: move Australia to another location in the Pacific. Please, tell us how is this down? best regards Dietmar @atteggiani @dkhutch ---
**Author:** ![atteggiani](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/atteggiani/32/212_2.png) [@atteggiani](https://forum.access-hive.org.au/u/atteggiani)\ **Post date:** [21 March 2023 00:48 UTC](https://forum.access-hive.org.au/t/access-coupled-n48-issue-1-change-topography-bathymetry-and-land-mask/574/2 "2023-03-21T00:48:13Z")
Hi @Dietmar_Dommenget, To create the land-mask files (for both ocean and atmosphere grid) from the bathymetry file, you will need to use a tool (`make_topog`) available inside the [ACCESS-OM2 repo](https://https://github.com/COSIMA/access-om2). I would suggest first step is to produce those files to run a Ocean-only (MOM standalone) or maybe Ocean-SeaIce (ACCESS-OM2) simulation with your changed continent displacement. Then, after that step is done, you can produce the atmosphere ancillary files (based on the land-mask file you created) and run a coupled simulation. I am going to do this exact step so I can learn more about the ocean input files and how the whole process works. I will start by running an ACCESS-OM2 (1° with 50 vertical levels) historical simulation using pre-made input files, and then repeat the same kind of simulation by creating my own (ocean) input files from scratch (starting with the creation of land-mask file from bathymetry). I will keep you updated on the entire workflow. Cheers Davide ---
**Author:** ![dkhutch](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/dkhutch/32/510_2.png) [@dkhutch](https://forum.access-hive.org.au/u/dkhutch)\ **Post date:** [21 March 2023 01:03 UTC](https://forum.access-hive.org.au/t/access-coupled-n48-issue-1-change-topography-bathymetry-and-land-mask/574/3 "2023-03-21T01:03:51Z")
Thanks Davide! Further to Davide’s comments. The ‘make\_topog’ tool is found within the MOM5.1 repository (part of the ACCESS OM2). You can see the tool here: > **[MOM5/src/tools/make\_topog at master · mom-ocean/MOM5](https://github.com/mom-ocean/MOM5/tree/master/src/tools/make_topog)** > > master/src/tools/make\_topog ‘make\_topog’ takes an input file of ocean bathymetry (0 is land, depth is positive downwards) and interpolates it onto the ocean grid (defined by ocean\_hgrid.nc) I have used this on Gadi to do novel topographies using the GFDL CM2.1 coupled model (using the same ocean model). I don’t know how to do the ancillary files for the atmosphere, or the land model boundary conditions, hence those are the parts I’m hoping to learn. @Dietmar_Dommenget ---
**Author:** ![Aidan](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/aidan/32/42_2.png) [@Aidan](https://forum.access-hive.org.au/u/Aidan)\ **Post date:** [21 March 2023 22:11 UTC](https://forum.access-hive.org.au/t/access-coupled-n48-issue-1-change-topography-bathymetry-and-land-mask/574/4 "2023-03-21T22:11:09Z")
Note that this is also being discussed in this topic. Not exactly the same problem, but there is significant overlap. > [@Bathymetry for ocean model at any resolution](https://forum.access-hive.org.au/t/bathymetry-for-ocean-model-at-any-resolution/462): > > I know that bathymetry has been a pain in the neck and that people have evolved artistic talent in modifying bathymetry and opening/closing channels etc. Can we collect here the accumulated knowledge so that, e.g., CliMA’s efforts (cc @glwagner) don’t need to reinvent the wheel? Is these papers documented anywhere? What we would like to be able to do is to take the ETOPO super-high resolution bathymetry and be able to coarsen it to the resolution we want to run (e.g., 2, 1, 1/2, 1/4, 1/10, 1/1…