xancil settings causing nested forecast to fail

[shakka]

Hi Jeff (assuming you are the right person to talk to about this!)

I have been having some issues with my nested model runs failing on the first timestep, having 'ingested NaNs? or infinities' (i.e. one of the catch-all BICGSTAB errors). I have narrowed the error down and discovered that the model is unhappy with my custom-made land-sea mask.

I created the LSM and orography files together with xancil v 0.57. The UM accepts the orography ancil fine, but when I use the new LSM rather than the UM defaults, it causes this crash.

Are you able to advise me regarding the necessary settings to produce a functional LSM file that the model will accept? I have tried no end of combinations but haven't settled on one that works.

My xancil job can be found at /projects/polar/elgil/ancils/hindcast_ancils/make_hindcast_ancils.job

This is quite urgent as I need to get several runs done soon using this domain.

Thanks very much in advance,
Ella

[jeff]

Hi Ella

Does your new LSM match your other ancillary files? If an ancillary file has missing data for land or sea points and your new LSM has changed any points from land to sea or sea to land, then the model will be reading missing data values as real data values.

Jeff.

[shakka]

Hi Jeff,

The orography and LSM match - are you suggesting that I would need to run in 'make ancils only' mode to get the UM to produce other ancils consistent with this LSM? Do you think that would work?

Best,
Ella

[shakka]

Hi Jeff,

I tried this, and it has successfully run a complete forecast.

Just to write what I did down for posterity:

• ran the suite in 'make ancils only' mode
• Paused the suite during the ANCIL_CAP stage after the ANCIL_TOP step but before any other ancils were actually created
• Reset the status of orography and LSM to 'succeeded' to prevent the UM making new LSM/orography
• Unpaused the suite and allowed it to continue making ancils
• created symbolic links to my custom ancils in the ~/cylc-run/<suite-id>/share/data/ancils/<domain>/<res> directory using the names the UM expects (qrparm.mask and qrparm.orog) - I also had to create a symlink to qrparm.orog.mn —> qrparm.orog
• Changed the suite to run using 'ancils made during a previous run of this suite'

Cheers,
Ella

[jeff]

Glad you got this working, and thanks for the explanation of how to do it.