Nan Error When Prescribing Land Use

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Hi,

I keep getting the EG_BICGSTAB (NaNs in error term in BiCGstab after 1 iterations) or the North/South halos too small for advection error when attempting to prescribe PFT fraction (stash 216) in a Archer2 run (u-cp508). I have run with Diagnostic Print Status but can’t see any obvious solution. The suite runs for ~10 mins before crashing.

u-cp508 is coupled and I am overwriting the land use generated by Triffid to investigate a particular LU scenario. I know this general approach works as I have had coupled Archer2 suites (with Triffid on) (e.g. u-cp448) succeed when prescribing LULC derived from UKESM CMIP6 model output (e.g. u-be690_m01s00i216_2015-2100_monthly_timeseries_land_cover_frac.anc.nc).

However, in this case I am trying to prescribe LULC from a scenario I have developed from an external source (CESM). I did the necessary PFT conversions, created a netCDF file and used xancil to make the ancil file (/work/n02/n02/jweber/Ancils_CESM_Land/Timeseries/maxforest_216_timeseries_OUT.anc). I followed Jeff’s advice in Using xancil and xconv to create timeslice ancillary files for this. The maxforest_216_timeseries_OUT.anc fails on Archer2 but succeeds when run in coupled suites on Monsoon (e.g. u-cn793). I have looked at the ancil in xconv and it looks reasonable.

To test my processing code, I extracted the raw data from the UKESM model derived stash (u-be690_m01s00i216_2015-2100_monthly_timeseries_land_cover_frac.anc.nc) and ran this through my processing script - u-cp508 ran fine with the resulting ancil. I’ve also done further tests where I duplicated the UKESM data and replaced one PFT field with the field corresponding field from my new data - this also caused the model to crash.

This is quite confusing as the new ancil file runs on Monsoon and makes me think I may need to adjust my Archer2 suite.

Would you have any suggestions?

Many thanks for your help,

James

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Just an update on this, it is only a problem when i_co2_opt = 3 / l_co2_interactive = True and I think it is being caused by a sudden large change in the PFT land cover (stash 216). From adding various print statements to my branch (dev/jamesweber/vn12.1_base) I think the error is occurring in the UM code somewhere after atmosphere/convection/tracer_total_var.F90 and before atmosphere/dynamics_diagnostics/sl_tracer_norm.F90. Is there any documentation about the order in which modules are called in the UM?

On a separate issue, I’ve trying to setup pptransfer to Jasmin but one links on the CMS webpage discussing this doesn’t seem to be working. The main page is
UKESM1.1-coupled Release Notes and the link is https://cms.ncas.ac.uk/_archer2/pptransfer. Could you point me to the update version of this page?

Many thanks,

James

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Hi James,

In answer to your pptransfer question there’s an extraneous _ in the link: https://cms.ncas.ac.uk/archer2/pptransfer.

I’ll fix the UKESM page shortly.

Cheers,
Ros.

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Great, thanks Ros, I’ll give that a go.

James