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: iboutle
Code Reviewer: Alistair Pirrie (@mo-alistairp)

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trac.log

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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?

iboutle

Hi Byron,

Sorry, quite a few comments to address - let me know if anything need clarification or you need any help on anything.

Cheers

Ian

iboutle · 2026-05-27T15:05:28Z

+    real(kind=r_def) :: pressure
+
+
+    g_over_rd = gravity / rd


I would suggest enabling and using this from nterfaces/physics_schemes_interface/source/constants/planet_constants_mod.F90 instead of calculating it every time

iboutle · 2026-05-27T15:21:42Z

+    pressure = min(isa_press_bot, pressure)
+
+    ! Missing or invalid data?
+    if (pressure == rmdi .or. pressure <= 0.0_r_def) then


This line differs from the UM code, and pressure=0 has already been excluded as an option by L106. I think the purpose of this line is to catch points where there is no convective cloud, but I don't think that will be happening, because of how the cloud base/top pressure is set in conv_gr and conv_comorph kernel. I think the .or. statement should be removed, and conv_gr/conv_comorph kernels should be modified to set pres_cv_base and pres_cv_top to rmdi instead of 0 when there is no convective cloud.

iboutle · 2026-05-27T15:24:56Z

@@ -0,0 +1,143 @@
+!-------------------------------------------------------------------------------


This kernel has no doxygen comments - please see an example of another kernel for where/how to add brief, details and @param descriptions.

The kernel also has no unit test, and probably should have

iboutle · 2026-05-27T15:25:27Z

+module aviation_icao_heights_kernel_mod
+
+  use argument_mod,         only: arg_type,            &
+                                  gh_field, gh_scalar, gh_logical, &


Suggested change

gh_field, gh_scalar, gh_logical, &

gh_field, &

iboutle · 2026-05-27T15:25:39Z

+
+  use argument_mod,         only: arg_type,            &
+                                  gh_field, gh_scalar, gh_logical, &
+                                  gh_read, gh_write, gh_integer, &


Suggested change

gh_read, gh_write, gh_integer, &

gh_read, gh_write, &

iboutle · 2026-05-27T15:53:46Z

+    if (nplev <= 0) then
+      message = 'Section 20: No pressure levels'
+      call log_event( message, log_level_error )
+      return


log_level_error should terminate the model, so the returns are redundant

iboutle · 2026-05-28T12:59:14Z

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


I think you're right, this loop isn't needed and can be removed

iboutle · 2026-05-28T12:59:55Z

+
+      gph_1000 = plev_geopot(source_map(df) + i1000-1)
+
+      if (thickness_850_flag .and. i850 /= -1) then


i850 /= -1 should already be guaranteed by the algorithm checks, so this could be removed

iboutle · 2026-05-28T13:02:13Z

+    if ( snow_probability_flag ) then
+      message = 'Section 20: snow probability requested'
+      call log_event( message, log_level_debug )
+      call invoke( setval_c(snow_probability, 0.0_r_def))


I don't think these pre-initialisations to 0 or 1 are needed, because the field is entirely written to inside the kernel, so can be removed

iboutle · 2026-05-28T13:21:50Z

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


Please can you remove this, and add the diagnostics in their correct place in the list above. That place is:

snow probability in the instant group of standard level fields - Hourly

the rest in the instant group of standard level fields - 3 Hourly

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

View reviewed changes

finishing touches

12b13dd

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

View reviewed changes

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

View reviewed changes

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

View reviewed changes

iboutle requested changes May 28, 2026

View reviewed changes


		call conv_cloud_base_icao_height%write_field()

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

		@@ -0,0 +1,143 @@
		!-------------------------------------------------------------------------------


		gph_1000 = plev_geopot(source_map(df) + i1000-1)

		if (thickness_850_flag .and. i850 /= -1) then

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

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