# Postproc\_atmos failure: IndexError

**URL:** <https://cms-helpdesk.ncas.ac.uk/t/postproc-atmos-failure-indexerror/1855>\
**Category:** Unified Model\
**Tags:** ARCHER2\
**Created:** [30 October 2025 13:38 UTC](https://cms-helpdesk.ncas.ac.uk/t/postproc-atmos-failure-indexerror/1855 "2025-10-30T13:38:52Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![earbsn](https://avatars.discourse-cdn.com/v4/letter/e/aeb1de/32.png) [@earbsn](https://cms-helpdesk.ncas.ac.uk/u/earbsn)\
**Post date:** [30 October 2025 13:38 UTC](https://cms-helpdesk.ncas.ac.uk/t/postproc-atmos-failure-indexerror/1855/1 "2025-10-30T13:38:52Z")

</div>

Hi, I am running the suite called ‘fixed’ (a copy of u-dc838). It has ran the first 5 years but has failed on the atmosphere post-processing step of the 1st year with an IndexError as part of create\_um\_mean function in atmos\_transform.py.

```auto
Traceback (most recent call last):
  File "/work/n02/n02/earbsn/cylc-run/fixed/share/fcm_make_pp/build/bin/main_pp.py", line 119, in <module>
    main()
  File "/work/n02/n02/earbsn/cylc-run/fixed/share/fcm_make_pp/build/bin/main_pp.py", line 112, in main
    run_postproc()
  File "/work/n02/n02/earbsn/cylc-run/fixed/share/fcm_make_pp/build/bin/main_pp.py", line 83, in run_postproc
    getattr(model, meth)()
  File "/mnt/lustre/a2fs-work2/work/n02/n02/earbsn/cylc-run/fixed/share/fcm_make_pp/build/bin/timer.py", line 115, in wrapper
    out = function(*args, **kw)
  File "/mnt/lustre/a2fs-work2/work/n02/n02/earbsn/cylc-run/fixed/share/fcm_make_pp/build/bin/atmos.py", line 491, in do_meaning
    icode = self.update_meanfile(meanfile, setend)
  File "/mnt/lustre/a2fs-work2/work/n02/n02/earbsn/cylc-run/fixed/share/fcm_make_pp/build/bin/timer.py", line 115, in wrapper
    out = function(*args, **kw)
  File "/mnt/lustre/a2fs-work2/work/n02/n02/earbsn/cylc-run/fixed/share/fcm_make_pp/build/bin/atmos.py", line 445, in update_meanfile
    rcode = climatemean.create_mean(meanfile,
  File "/mnt/lustre/a2fs-work2/work/n02/n02/earbsn/cylc-run/fixed/share/fcm_make_pp/build/bin/timer.py", line 115, in wrapper
    out = function(*args, **kw)
  File "/mnt/lustre/a2fs-work2/work/n02/n02/earbsn/cylc-run/fixed/share/fcm_make_pp/build/bin/climatemean.py", line 256, in create_mean
    icode, output = target_app(meanfile, **kwargs)
  File "/mnt/lustre/a2fs-work2/work/n02/n02/earbsn/cylc-run/fixed/share/fcm_make_pp/build/bin/timer.py", line 115, in wrapper
    out = function(*args, **kw)
  File "/mnt/lustre/a2fs-work2/work/n02/n02/earbsn/cylc-run/fixed/share/fcm_make_pp/build/bin/atmos_transform.py", line 323, in create_um_mean
    ','.join([str(i) for i in ff_out.fields[0].raw[1:7]]),
IndexError: list index out of range
[FAIL] main_pp.py atmos <<' __STDIN__'

```

I then put some print statements in create\_um\_mean to look at ff\_out.fields, where the IndexError is coming from and looked at job.out and it returned this:

```auto
[INFO] ATMOS SHARE directory: /work/n02/n02/earbsn/cylc-run/fixed/share/data/History_Data
[INFO] ATMOS WORK directory: /work/n02/n02/earbsn/cylc-run/fixed/work/22770101T0000Z/coupled
[INFO] Running do_meaning for atmos...
[INFO] Creating meanfile fixeda.ps2277jja with components:
	/work/n02/n02/earbsn/cylc-run/fixed/share/data/History_Data/fixeda.pm2277aug
	/work/n02/n02/earbsn/cylc-run/fixed/share/data/History_Data/fixeda.pm2277jul
	/work/n02/n02/earbsn/cylc-run/fixed/share/data/History_Data/fixeda.pm2277jun
[INFO] Meanfile validity date: 2277,9,1,0 day number 241
<FieldsFile: integer_constants=(46,), real_constants=(38,), level_dependent_constants=(86, 8)>
[]

```

so this list is empty, but I’m not sure why that would be the case. I’m not sure how to move forward from here, so any help is appreciated. Thank you!

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<div class="post-metadata">

**Author:** ![RosalynHatcher](https://dub1.discourse-cdn.com/flex013/user_avatar/cms-helpdesk.ncas.ac.uk/rosalynhatcher/32/11_2.png) [@RosalynHatcher](https://cms-helpdesk.ncas.ac.uk/u/RosalynHatcher)\
**Post date:** [3 November 2025 15:56 UTC](https://cms-helpdesk.ncas.ac.uk/t/postproc-atmos-failure-indexerror/1855/3 "2025-11-03T15:56:03Z")

</div>

Hi Brooke,

What are the differences between your suite “fixed” and the original u-dc838? I am a bit confused by what “fixed” actually is. It appears to be a branch of Helen’s suite u-ds156 but it’s description says a copy of u-dc838?? The postproc\_atmos task runs fine in the suite u-dc838. So it’s definitely something to do with changes that have been made subsequently.

Cheers,  
Ros

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<div class="post-metadata">

**Author:** ![earbsn](https://avatars.discourse-cdn.com/v4/letter/e/aeb1de/32.png) [@earbsn](https://cms-helpdesk.ncas.ac.uk/u/earbsn)\
**Post date:** [4 November 2025 11:17 UTC](https://cms-helpdesk.ncas.ac.uk/t/postproc-atmos-failure-indexerror/1855/4 "2025-11-04T11:17:37Z")

</div>

Hi Ros, thanks for your help. One of the differences was calculating seasonal means, which is the part it was getting stuck on, so I just changed that to false.

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<div class="post-metadata">

**Author:** ![system](https://europe1.discourse-cdn.com/flex013/uploads/cms_support/original/1X/1fd2411499ffcbc299fe756cd5cdf26e44956558.png) [@system](https://cms-helpdesk.ncas.ac.uk/u/system)\
**Post date:** [4 December 2025 11:17 UTC](https://cms-helpdesk.ncas.ac.uk/t/postproc-atmos-failure-indexerror/1855/5 "2025-12-04T11:17:42Z")

</div>

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