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Ticket Resolution Summary Owner Reporter
#110 fixed 1km simulation failing to converge lois gdevine
Description

Hi,

I have just run a 1km resolution simulation for a region of Africa. Unfortunately the model produces 'junk'

output from the very first timestep and in the .leave file shows this….

Atm_Step: Timestep 1 ============================================== initial Absolute Norm : 3.63954480017502346 GCR( 2 ) failed to converge in 200 iterations. Final Absolute Norm : 0.687325985659843416E-02 ==============================================

I have had similar problems before at 12km but was able to get around it by (1) halving the timestep and (2) upping the number of iterations in the GCR. I have tried this with the 1km but it doesn't appear to help (timestep currently at 2.5 minutes). Do you have any suggestions as to what may be wrong here? The LBCs from the 4km run, ancillary files, and the generated start dump (.astart) all look okay. Is it possible that some of my ancillary files are not compatible with each other. Currently most of the ancillaries are provided by the start dump, except for orography/ozone/land-sea mask. The run ID is xcrfg.

Any help much appreciated. Gerry

#3027 answered 2015 onwards ancillaries and BICGSTAB error um_support Leighton_Regayre
Description

Hello,

I'm having trouble locating the source of some BICGSTAB errors I believe are associated with ancillary files. The errors are of the form: NaNs? in error term in BiCGstab after 1 iterations

My suite u-bm992 has been adapted from a working suite (itself adapted from the UKESM1 release) to run from 20150101 (on ARCHER), so that I can make an ensemble for a specific year. Wind fields are nudged in the suite and it uses the Gregorian calendar.

The suite uses files in this folder for SST and seaice: /work/n02/n02/ukca/ancil/n96e/reynolds/n96e_gregorian_1981_2019/

Because it is nudged, it also uses wind fields from: /work/n02/n02/ukca/analyses/era-in/ However, this is unchanged since the folder contains wind fields through to 2019 and has a file for 20150101.

I've also altered the restart filename: /work/y07/y07/umshared/ukesm/restarts/bd256a.da20150101_00 and updated the model basis time to match: 20150101T0000Z

All other ancillaries are climatologies so shouldn't be causing NaN errors.

Any advice on how to track down the source of this error would be very welcome. I've run the suite with the highest level of diagnostic output.

Thanks,

Leighton.

#473 fixed 3 ecmwf startdumps required willie anmcr
Description

Hi,

I need 3 ECMWF ERA40 startdumps. The dates are

1) 19830214 00Z 2) 19840823 00Z 3) 19850915 00Z

Thanks,

Andrew

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