CESM2 piControl: changed PE layout after ~12 years — does it affect ENSO statistics？

[CCl]

Hi everyone,
I’m running CESM2 B1850cmip6 piControl. I ran ~12 model years with one PE layout, then continued from the same restart but changed the PE layout (9 nodes → 18 nodes; total cores ~574, different decomposition).
As a quick test, starting from the same restart I ran ~3 months with both layouts and the patterns diverge noticeably.
Is this expected (round-off + chaos)? More importantly, is it scientifically acceptable to change PE layout mid-run for a long piControl, or could it bias long-term statistics such as ENSO (Niño3.4 variance/spectrum) beyond losing bit-for-bit reproducibility?

 

[islas]

Changing the PE layout mid-run shouldn't result in changes in the climate, so it shouldn't bias the long-term statistics of ENSO variance beyond the loss of bit-of-bit reproducibility..

 

[CCl]

Thanks a lot for the clarification, islas. That’s very helpful — I’ll proceed with the mid-run PE layout change and focus on long-term statistics rather than bit-for-bit reproducibility.

Changing the PE layout mid-run shouldn't result in changes in the climate, so it shouldn't bias the long-term statistics of ENSO variance beyond the loss of bit-of-bit reproducibility..