Stable diags #11, #21, #24 by bblay-mo · Pull Request #483 · MetOffice/lfric_apps

Byron Blay (bblay-mo) · 2026-05-06T11:28:24Z

PR Summary

Three Section 20 aviation diagnostics created from plev_geopot.

Output from suite u-dy804:

geopotential thickness

snow probability

(That ticket contains a incorrect link to the um code, which should be pws_snow_prob_diag.F90.)

icao cloud heights

Note: we have not found a UM Section 20 example of these two fields for comparison.

Sci/Tech Reviewer:
Code Reviewer: Alistair Pirrie (@mo-alistairp)

Code Quality Checklist

I have performed a self-review of my own code
My code follows the project's style guidelines
Comments have been included that aid understanding and enhance the readability of the code
My changes generate no new warnings
All automated checks in the CI pipeline have completed successfully

Testing

I have tested this change locally, using the LFRic Apps rose-stem suite
If any tests fail (rose-stem or CI) the reason is understood and acceptable (e.g. kgo changes)
I have added tests to cover new functionality as appropriate (e.g. system tests, unit tests, etc.)
Any new tests have been assigned an appropriate amount of compute resource and have been allocated to an appropriate testing group (i.e. the developer tests are for jobs which use a small amount of compute resource and complete in a matter of minutes)

trac.log

Security Considerations

I have reviewed my changes for potential security issues
Sensitive data is properly handled (if applicable)
Authentication and authorisation are properly implemented (if applicable)

Performance Impact

Performance of the code has been considered and, if applicable, suitable performance measurements have been conducted

AI Assistance and Attribution

Some of the content of this change has been produced with the assistance of Generative AI tool name (e.g., Met Office Github Copilot Enterprise, Github Copilot Personal, ChatGPT GPT-4, etc) and I have followed the Simulation Systems AI policy (including attribution labels)

Documentation

Where appropriate I have updated documentation related to this change and confirmed that it builds correctly

PSyclone Approval

If you have edited any PSyclone-related code (e.g. PSyKAl-lite, Kernel interface, optimisation scripts, LFRic data structure code) then please contact the TCD Team

Sci/Tech Review

I understand this area of code and the changes being added
The proposed changes correspond to the pull request description
Documentation is sufficient (do documentation papers need updating)
Sufficient testing has been completed

(Please alert the code reviewer via a tag when you have approved the SR)

Code Review

All dependencies have been resolved
Related Issues have been properly linked and addressed
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Code quality standards have been met
Tests are adequate and have passed
Documentation is complete and accurate
Security considerations have been addressed
Performance impact is acceptable

Byron Blay (bblay-mo) · 2026-05-14T14:35:52Z

+  real(r_def), parameter :: isa_press_bot = 101325.0_r_def
+
+  ! Pressure (Pa) at 11,000 gpm.
+  real(r_def), parameter :: isa_press_mid = 22632.0_r_def


Claude says isa_press_mid should be 22632.1 and isa_press_top should be 5474.89. Should we do anything?

Byron Blay (bblay-mo) · 2026-05-14T14:37:12Z

+    ! Subtract geopotential heights at 850 and 500 hPa from that at 1000 hPa.
+    !
+    ! Snow probability:
+    ! Implement Boyden (1964), using 850 and 1000 hPa.


Claude doesn't ... "think" the code further down matches the Boyden equation.

Byron Blay (bblay-mo) · 2026-05-14T14:38:31Z

+
+      call conv_cloud_base_icao_height%write_field()
+
+      ! Is it necessary/safe to remove this field now?


Need steering on this question please.

Byron Blay (bblay-mo) · 2026-05-14T14:45:33Z

+
+
+    ! Process every DOF in this cell.
+    do df = 1, result_ndf


Might be worth having a chat/steer about if/when we can skip this loop, as does the other kernel in this PR.

Byron Blay (bblay-mo) · 2026-05-14T14:47:03Z

+  ! Lapse rate (degreeC/km) for levels below 11,000 gpm.
+  real(r_def), parameter :: isa_lapse_ratel = 6.5e-03_r_def
+
+  ! Lapse rate (degreeC/km) for levels above 20,000 gpm.


This comment, as copied from the UM, said 11,000. Claude spotted the error. Worth mentioning just in case.

Byron Blay (bblay-mo) · 2026-05-15T08:30:15Z

+      if(snow_probability_flag .and. i850 /= -1) then
+        gph_850 = plev_geopot(source_map(df) + i850-1)
+        snow_probability(result_map(df)) = &
+          5220.0_r_def + 3.86666_r_def*gph_1000 - 4.0_r_def*gph_850


The earliest I've been able to track these magic numbers so far is here.

Byron Blay (bblay-mo) · 2026-05-15T14:39:18Z

 	<field field_ref="forcing__dt_force" />
      </file>

+	<file id="lfric_aviation" name="lfric_aviation" output_freq="6h" convention="UGRID" enabled=".TRUE.">


Couldn't find documentation for the <file> and <field_group> tags.

Byron Blay (bblay-mo) · 2026-05-15T14:41:57Z

+    </field_group>
+
+    <!-- Section 20 Aviation diagnostics -->
+    <field_group operation="instant" freq_op="6h">


KGO? I got the impression there isn't any yet?

Byron Blay (bblay-mo) · 2026-05-20T09:35:39Z

    plev_geopot_clim_flag = diag_samp('plev__geopot_clim')
-    plev_geopot_flag = init_diag(plev_geopot, 'plev__geopot', activate=plev_geopot_clim_flag)
-    if ((plev_geopot_flag .or. plev_geopot_clim_flag) .and. use_xios_io) then
+    plev_geopot_flag = init_diag(plev_geopot, 'plev__geopot', &


Just an observation: From a software engineering perspective, this module (and others) should probably not know anything about the aviation module. I think it's a pattern which can lead to a rat's nest of dependencies. One solution might be to express field dependencies in a centralised place, which init_diag could check for itself, without needing the activate arg. Is that worth raising in a ticket somewhere?

Byron Blay (bblay-mo) added 6 commits April 30, 2026 09:00

s20 diag thickness

f0a35d6

tidy

6c2c3b7

lower case

e3cdd7d

S20 icao heights

4744307

running to completion locally

dbb50d1

S20 snow prob

f753421

github-actions Bot added the cla-signed The CLA has been signed as part of this PR - added by GA label May 6, 2026

github-actions Bot assigned Byron Blay (bblay-mo) May 6, 2026

Byron Blay (bblay-mo) added 3 commits May 11, 2026 16:57

running locally

436d987

turn things off until it runs

a2e5556

put stuff back on

8f31833

This was referenced May 13, 2026

S20 Diags: snow prob #120

Closed

S20 Diags: icao heights #169

Closed

S20 Diags: geopot thickness #454

Closed

Byron Blay (bblay-mo) added 3 commits May 14, 2026 09:51

icao heights gpm to kft

efb9da4

name fix

68d0af0

finishing touches

6c0d132

Byron Blay (bblay-mo) commented May 14, 2026

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finishing touches

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Byron Blay (bblay-mo) commented May 14, 2026

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Byron Blay (bblay-mo) commented May 15, 2026

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snow prob clamp

8372788

Byron Blay (bblay-mo) force-pushed the stable_diags_11_21_24 branch from 79ea31a to 8372788 Compare May 19, 2026 08:41

Byron Blay (bblay-mo) marked this pull request as ready for review May 20, 2026 09:22

Byron Blay (bblay-mo) requested a review from iboutle as a code owner May 20, 2026 09:22

Byron Blay (bblay-mo) requested a review from a team as a code owner May 20, 2026 09:22

Byron Blay (bblay-mo) requested review from Ricky Wong (mo-rickywong) and removed request for a team May 20, 2026 09:22

Byron Blay (bblay-mo) commented May 20, 2026

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Stable diags #11, #21, #24#483

Stable diags #11, #21, #24#483
Byron Blay (bblay-mo) wants to merge 14 commits into
MetOffice:mainfrom
bblay-mo:stable_diags_11_21_24

Byron Blay (bblay-mo) commented May 6, 2026 •

edited by james-bruten-mo

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		call conv_cloud_base_icao_height%write_field()

		! Is it necessary/safe to remove this field now?

Conversation

Byron Blay (bblay-mo) commented May 6, 2026 • edited by james-bruten-mo Loading Uh oh! There was an error while loading. Please reload this page.

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PR Summary

geopotential thickness

snow probability

icao cloud heights

Code Quality Checklist

Testing

trac.log

Security Considerations

Performance Impact

AI Assistance and Attribution

Documentation

PSyclone Approval

Sci/Tech Review

Code Review

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