Regional configs to read input data using new XIOS API for time varying fields #615

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1. Ricky Olivier (ricky-lv426)

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   enhancementNew feature or requestNew feature or request

   on Jul 13, 2026
2. Ricky Olivier (ricky-lv426)

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   issue type on Jul 13, 2026
3. Ricky Olivier (ricky-lv426)

   changed the title [-]Regional modelling configs to read input data at user defined timestamps or time windows[/-] [+]Regional configs to read input data at user defined timestamps or time windows[/+] on Jul 13, 2026
4. Iva Kavcic (TeranIvy)

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   Ed Hone (EdHone)

   on Jul 13, 2026
5. Ricky Olivier (ricky-lv426)

   changed the title [-]Regional configs to read input data at user defined timestamps or time windows[/-] [+]Regional configs to read input data using new XIOS API for time varying fields[/+] on Aug 26, 2026
6. ricky-lv426 commented on Aug 26, 2026

   

   Ricky Olivier (ricky-lv426)

   on Aug 26, 2026

   Last edited by ricky-lv426

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   Implementation plan (tentative)

   Technical details

   Inspection of lfric_core clarified a few things.

   • lfric_xios_file_type owns an embedded temporal_type
   • fields_in_file attaches every field in the supplied collection to that file
   • freq is a file operation cadence in timesteps, not a time-slice count
   • the temporal cache window is internal to temporal_type
   • update_freq controls model-field refresh cadence and whether interpolation is enabled

   This means a migrated ancillary file must be given a dedicated field collection containing only the fields present in that file.

   Also the following is noted:

   The new path does not currently expose a public window caching setting.

   Inside lfric_core/components/lfric-xios/source/lfric_xios_temporal_mod.x90, the cache window is derived automatically:

   • start from window_size = 1
   • add one slice if the context start is not exactly on a file timestamp
   • add one slice if interpolation is required

   So the effective cache is currently 1, 2, or 3 slices depending on alignment and interpolation.

   This is different from the legacy time_axis_type path, where window_size could be passed explicitly and defaults to 3.

   Also the update_freq is an integer time enum passed into lfric_xios_file_type and converted inside duration_from_enum(...):

   • update_freq=0 disables interpolation and updates the model field only at file time points
   • update_freq/=0 enables interpolation and updates the model field on the requested cadence

   Some keyword meanings:

   Term	Path	Meaning
   pop_freq	legacy time_axis_type	how often cached ancillary data is pushed into the live model field
   interp_flag	legacy time_axis_type	whether to interpolate between neighbouring time entries
   freq	file-owned lfric_xios_file_type	how often the file gets a read/write opportunity in model timesteps
   update_freq	file-owned lfric_xios_file_type	how often the live model field is refreshed from the temporal cache
   internal window_size	file-owned temporal_type	how many time slices are cached in memory

   Way forward

   The tentative plan for each migrated ancillary file is to:

   • register the file with operation=OPERATION_TIMESERIES
   • pass a field collection containing only the fields in that file
   • let the file-owned temporal_type manage the cache and model-field updates
   • stop attaching those fields to legacy time_axis_type objects
   • remove any driver logic that still depends on that time axis for the migrated file

   The main setup point for this would be science/gungho/source/driver/gungho_setup_io_mod.F90.

   Issues/details to clarify

   • How to map old user tunable functionality where the window_size could be passed explicitly, to in hidden window cache size setting of the new api.