Reconfiguration fails with 2022 analysis files (UM vn12.0 nested suite)

Dear CMS Helpdesk

I’m running a UM vn12.0 nesting suite on Monsoon (u-cl358), although at the moment I’m just running the global model, without any nested regions. My starting point was suite u-by395, as recommended in the Nesting Suites guide.

The suite runs without problems when using operational analysis files from 2020 (either using archived analysis files or analyses on disk), but when I switch to a 2022 start date I get the following error during the reconfiguration step:

? Error code: 6174
? Error from routine: RCF_CALC_TILES
? Error message: Try two-step recon: Change in grid for n-to-1 not currently supported for STASHcode 231

Looking at the log files, I can see that STASHcode 231 refers to SNOW GRAIN SIZE ON TILES MICRONS. However, this field is present in both 2020 and 2022 analysis files, so I’m not sure what the problem is. Do you have any idea on how to solve this issue?

Many thanks for the support and best wishes
Ambrogio

Hi @grenville, is this the right place for this query? If not, where should I post it?

Many thanks!
Ambrogio

Hi Ambrogio

This is the right place - we’ve not answered yet because we don’t know the answer – this is completely new to us.

Grenville

Hi Grenville,
Thanks a lot for getting back to me so quickly. Are there any more details that I could give you to help finding out what the problem is. Do you know of any possible temporary workarounds? (probably not, given that it’s the first time you see this error?)

Thanks!
Ambrogio

Hi Ambrogio

I’ve had a quick look at this and the problem is caused because your model run wants the SNOW GRAIN SIZE field on a single tile but your input dump has it on 9 tiles (in the 2020 dumps it was on 1 tile which is why they worked ok) and the reconfiguration doesn’t know how to handle this.

I’m not sure what configuration changes you would need to make to use 9 tiles in your run or if you would even want to do this.

I’m also not sure how you would use the reconfiguration in two-step mode, but I could look into this further.

Do you have any Met Office contacts who might know anything about this?

Jeff.

Looking at the code you only get the above error if you are going from multiple tiles to one tile and you are doing horizontal interpolation, so I guess two-step mode means running the reconfiguration once to do the horizontal interpolation then running it again to do the tile changes. I would need to look into this further if you wanted to go down this route.

Jeff.

Hi Jeff,

Thank you very much for your replies. I am not really interested in the SNOW GRAIN SIZE field, so I don’t really mind if my runs end up using 1 tile instead of 9. Yes, it would be great if you could look into the two-step mode of running the reconfiguration, but if you prefer looking into different solutions that’s also fine. The suite I’m using is based on the regional nesting suite (u-by395), so I guess that Claudio Sanchez could be a suitable contact at the Met Office.

Please let me know if there is anything I could do to help, and many thanks for your support.

Best wishes
Ambrogio

Dear Jeff,

Is there anything I can do now, or should I just wait for you to provide instructions on how to run the reconfiguration in two-step mode? (I tried having a look myself, but I have really no idea on what to do)
If so, could you give me a tentative timeframe for receiving those instructions?

Many thanks again for the support and best wishes
Ambrogio

Hi Ambrogio

I’ve tried a couple of things to see if I could get this to work in two-step mode but without success, I’m not really sure what to try next. The only thing I can suggest is to contact someone in the Met. Office to see if they can help, maybe you could try the contact you mentioned?

Jeff.

Hi Jeff,

Many thanks for trying this. I have just contacted Claudio Sanchez at the Met Office. When we (hopefully) find a solution, I would post it here for future reference (I assume at some point someone else will want to use the regional nesting suite with 2022 initial data)

Best wishes
Ambrogio

Hi Jeff, Grenville,

Coming back to this ticket as there is now a solution. For start data from May 2022 onwards the solution is to switch to the newest version of the regional nested suite, using GA8 and GL9. More info here: #324 (RNS: Add the Global GA8GL9 configuration) – Regional Model Evaluation and Development (metoffice.gov.uk).

The suite that needs to be copied is u-by395/add_ga8gl9_config@241565 (previous revisions fail due to ancillaries not being consistent with updated model settings).

I hope this can be useful to other users.

Thanks for the support and best wishes
Ambrogio