Opened 2 years ago

Closed 2 years ago

#2723 closed help (fixed)

Creating ozone ancillary using xancil

Reported by: charlie Owned by: jeff
Component: UM Tools Keywords:
Cc: Platform: NEXCS
UM Version:



Sorry, but I have another issue with xancil. I am trying to create an ozone ancillary file (from one I have modified), using the ozone option, but it giving me an error saying the standard_name does not have the right attributes. I don't understand this, because the meta data of my modified file should be absolutely identical to the original. I managed to get round the problem by using the generalised ancillary option and, although it works, produces the file on pseudo-levels (going from 1-85) rather than the hybrid_ht levels of the original. I don't know if this will matter when it comes to running the model, but I suspect yes.

Please would you advise on what is going wrong?

My files are on Nexcs at /home/d05/cwilliams/gc31/ancils/ozone/ukesm1_4xco2 where:

  • ukca_oxid_O3_u-aw447_clim_2318-2347_orig.anc = the original
  • = my modified version in netcdf
  • ukca_oxid_O3_u-aw447_clim_2318-2347.anc = the new version but containing the pseudo-levels



Change History (8)

comment:1 Changed 2 years ago by jeff

  • Owner changed from um_support to jeff
  • Status changed from new to accepted

Hi Charlie

Having the exact error message or a .job file, so I can reproduce the error, would make it easier to diagnose the problem.

I suspect you are having problems creating the vertical level values. Xancil has three ways to create these, two of which depend on the input netCDF file having the correct CF metadata. Your netCDF file doesn't have this metadata (which is what I suspect the error message was saying), so you need to use the third method.

In the Grid configuration panel click on "Specify atmosphere vertical levels" and enter the data needed to create vertical level values. The vertical level namelist file is the one your UM run uses, look in app/um/rose-app.conf for the vert_lev variable or search rose edit for this variable.

This web page has further information on this,, although it is a bit out of date referencing the umui instead of rose.


comment:2 Changed 2 years ago by charlie

Sorry Jeff, I have just rerun the job (and saved the job as ozone.job1 in the same directory) to reproduce the exact error. It is:

 Writing Ozone ancillary file ozone
 ERROR: variable hybrid_ht from NetCDF file 
 /home/d05/cwilliams/gc31/ancils/ozone/ukesm1_4xco2/ukca_oxid_O3_u-aw447_clim_23 doesn't contain the standard_name attribute needed to
  calculate vertical level values.

I am just about to search for the vertical levels as you suggested, but in the meantime I have been reading the documentation and noticed something about the version. The documentation says "For version numbers less than 5.0 the vertical coordinate type is hybrid sigma pressure, otherwise the vertical coordinate type is hybrid height". In my original file it is definitely using hybrid_ht, however when I open this original file using xconv it says it is version 0.9, so this is what I have been putting into xancil. Might this be the problem?


comment:3 Changed 2 years ago by charlie

I suppose a more pertinent question would be: when creating new ancillaries, should the version number in the general configuration box of xancil be the same as the original ancillary (in this case 0.9), or should it match the UM version I am using this ancillary with (in this case 10.7)?

comment:4 Changed 2 years ago by jeff

Hi Charlie

Your original ancillary file was created using the new Met Office ANTS code, I suspect, this will put the ANTS version number in the UM header instead of the UM version number. Xancil uses this version number to decide whether it creates pre UM5.0 ancillaries or not, so using the ANTS version number will give you the wrong ancillary file type.

Your latest message arrived as I was typing this, yes use 10.7 as the version number.

You will still need to use the "Specify atmosphere vertical levels" method as you file doesn't have the correct metadata.


comment:5 Changed 2 years ago by charlie

Excellent, understood, and understood about the version number to use.

I have now sorted the problem, I think, using the vertical level namelist file (which I found) that you suggested. I set both model levels and ozone levels to 85, and "is level data stored upwards" to yes, is this correct? Either way, it has worked and looks right.


comment:6 Changed 2 years ago by jeff

Yes it should be correct. If the number of ozone levels was different it would be in the same rose edit panel as vert_level or search for variables model_levels and ozone_levels.


comment:7 Changed 2 years ago by charlie

Great, I have just checked and they are indeed the same.

I will close the ticket, many thanks.

comment:8 Changed 2 years ago by charlie

  • Resolution set to fixed
  • Status changed from accepted to closed
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