Add snow_flux diagnostics at mon/daily/6hr/3hr/subhr frequencies (iss…

[Zubair Maalick (zmaalick)]

…ue #681)

Implements the snow_flux diagnostic (UM STASH m01s05i215, lbproc=128) across five output frequencies using the existing processed__total_snow registry field (= microphysics__ls_snow + convection__conv_snow, Group A XML expression):

• Daily mean over land: new Group A field processed__snow_flux_land (= processed__total_snow * surface__land_fraction) added to the daily averaged group in file_def_diags_gal_clim.xml.
• Monthly mean: processed__total_snow added to a new monthly output file (lfric_diagnostics_monthly, output_freq=1mo) in file_def_diags_gal_clim.xml.
• 6-hourly mean: processed__total_snow added to a new lfric_gl_std_levs_diags_6hr file block in file_def_diags_oper_nwp_gl.xml.
• 3-hourly mean: processed__total_snow (as total_snow_average) added to the existing lfric_gl_std_levs_diags_3hr average group in file_def_diags_oper_nwp_gl.xml.
• Sub-hourly: processed__total_snow added to a new lfric_gl_std_levs_diags_subhr file block (output_freq=1ts) in file_def_diags_oper_nwp_gl.xml.

Registry-only change; no Fortran/kernel/algorithm edits.

PR Summary

Sci/Tech Reviewer:
Code Reviewer: Andrew Coughtrie (@andrewcoughtrie)

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[github-actions]

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[iboutle]

As with #680, please revert changes to the rose-stem directory pending discussion with Jon about what we actually want to test here.

The addition of the land only diagnostics to field_def_diags could probably be a single PR to save reviewer time and effort.

[iboutle]

As with #680, please revert changes to the rose-stem directory pending discussion with Jon about what we actually want to test here.

The addition of the land only diagnostics to field_def_diags could probably be a single PR to save reviewer time and effort.

Same comment applies here as #680 whether we really want to be scaling the snow flux by the land fraction