Radaer api ukca side - part one run time by alanjhewitt · Pull Request #41 · MetOffice/ukca

Alan J Hewitt (alanjhewitt) · 2026-07-16T16:48:53Z

PR Summary

Sci/Tech Reviewer: Mohit Dalvi (@mcdalvi)
Code Reviewer: Yaswant Pradhan (@yaswant)

I developed the original lfric to radaer functionality in 2020. Like a lot of developments back then, it was needed in a hurry and so I developed a fudged solution with technical debt.

We will need user flexibility soon to be able to run radaer with different user settings, hence this part one of two development.

In part one, I have introduced the user flexibility that is required for run time. Its already a very large change, and this is a natural break point for splitting a big PR.

Some hard-coded settings remain in the development (on the ukca side, this is values like i_cpnt_index), which will be removed in the part two ticket to develop the initialisation stage functionality.

linked Radaer api la side - part one run time lfric_apps#636

Code Quality Checklist

(Some checks are automatically carried out via the CI pipeline)

I have performed a self-review of my own code
My code follows the project's style guidelines
Comments have been included that aid undertanding and enhance the
readability of the code
My changes generate no new warnings

Testing

I have tested this change locally, using the UKCA rose-stem suite
If shared files have been modified, I have run the UM and LFRic Apps rose
stem suites
If any tests fail (rose-stem or CI) the reason is understood and
acceptable (eg. kgo changes)
I have added tests to cover new functionality as appropriate (eg. system
tests, unit tests, etc.)

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

Sci/Tech Review

[X ] 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 (Also tested in UKCA Box model with not impact)

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
CLA compliance has been confirmed
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

Mohit Dalvi (mcdalvi) · 2026-07-22T11:57:37Z

+! Subroutine Interface:
+!
+! Code Owner: Please refer to the UM file CodeOwners.txt
+! This file belongs in section: TOP_LEVEL


For files in the UKCA repo, the owning Section is just 'UKCA'

Mohit Dalvi (mcdalvi) · 2026-07-22T11:58:58Z

+    l_exclude_lw,                                                              &
+    l_exclude_sw,                                                              &
+    ! Modal diameters from UKCA module (input)
+    ukca_dry_diam_um,                                                          &


Given that this is a LFRic-specific routine the '_um' suffix can be dropped.

Mohit Dalvi (mcdalvi) · 2026-07-22T12:02:37Z

+    aod_ukca_all_modes_um,                                                     &
+    aaod_ukca_all_modes_um )
+
+USE socrates_init_mod,                 ONLY: n_sw_band,                        &


This will introduce a SOCRATES dependency while building UKCA and interfere with stand-alone applications like the Box model. Is there an alternative way of passing these values?

Mohit Dalvi (mcdalvi) · 2026-07-22T12:06:01Z

+
+USE ukca_radaer_prepare_mod,           ONLY: ukca_radaer_prepare
+
+USE um_physics_init_mod,               ONLY: n_radaer_mode


um_physics_init_mod will introduce a LFRic dependency in the build. The value could be passed in as a ''configuration'' variable (glomap_config%)

Mohit Dalvi (mcdalvi) · 2026-07-22T12:07:17Z

+CHARACTER(LEN=*), PARAMETER, PRIVATE :: ModuleName = 'UKCA_RADAER_LFRIC_API_MOD'
+
+CONTAINS
+


A placeholder to remind that the routine needs to be exported to LFRic via ukca_api_mod

We spoke offline. Its not needed for part one, but I think this is needed for part two. Thanks for the spot though, as i would probably have missed this.

Mohit Dalvi (mcdalvi) · 2026-07-22T12:08:22Z

+                       l_aod_ukca_cor_ins, l_aaod_ukca_cor_ins
+
+! Mass thickness of layers
+REAL, INTENT(IN) :: d_mass_theta_levels_um( npd_profile, npd_layer )


As above the _um suffix should be dropped.

I got a build error after removing all examples of _um . There three pairs of variables with otherwise the same name with r_def and r_um equivalents ( scattering, asymmetry, absorption ). I gave the r_um version a suffix _radaer .

Mohit Dalvi (mcdalvi) · 2026-07-22T12:09:46Z

+IF (lhook) CALL dr_hook(ModuleName//':'//RoutineName, zhook_in, zhook_handle)
+
+  !-----------------------------------------------------------------------
+


A explainer on the order of the items (modes?) will help to identify which are valid or invalid for a particular component/species.

We spoke offline. I did not develop the unusual data layout of radaer_band_average and I agree that it is confusing. I put a comment in the code to give an idea of what is going on.

These hard coded values were moved from the LFRic RADAER kernel in this joint change.

In part two, I will remove these hard coded values and instead will calculate them during the initialisation step in the same way that is done in UM module ukca_radaer_init-ukca.F90

Mohit Dalvi (mcdalvi) · 2026-07-22T12:11:46Z

+
+  DO k = 1, npd_ukca_aod_wavel
+    DO i = 1, npd_profile
+      aod_ukca_all_modes_um(i,k,mode_ait_sol-1) = aod_ukca_this_mode_um(i,k)


An explanation on why the '-1' for the 3rd index is needed will help understanding. Will future additions to modes or change in order mean re-writing the indices?

Mohit Dalvi (mcdalvi) · 2026-07-22T12:12:43Z

+
+  DO k = 1, npd_ukca_aod_wavel
+    DO i = 1, npd_profile
+      aod_ukca_all_modes_um(i,k,mode_acc_sol-1) = aod_ukca_this_mode_um(i,k)


See above, using '-1' for indexing

Mohit Dalvi (mcdalvi) · 2026-07-29T11:23:09Z

Thanks Alan, Sci-tech Review passed
Tagging Yaswant Pradhan (@yaswant) for Code Review.

UKCA side changes

6e0dc98

Alan J Hewitt (alanjhewitt) requested a review from Mohit Dalvi (mcdalvi) July 16, 2026 16:48

Alan J Hewitt (alanjhewitt) added Linked Apps This PR is linked to a MetOffice/lfric_apps PR cla-signed The CLA has been signed as part of this PR - added by GA labels Jul 16, 2026

github-actions Bot assigned Alan J Hewitt (alanjhewitt) Jul 16, 2026

Alan J Hewitt (alanjhewitt) changed the title ~~UKCA side changes~~ Radaer api ukca side - part one run time Jul 16, 2026

Alan J Hewitt (alanjhewitt) mentioned this pull request Jul 16, 2026

Radaer api la side - part one run time MetOffice/lfric_apps#636

Open

28 tasks

Alan J Hewitt (alanjhewitt) requested a review from Yaswant Pradhan (yaswant) July 16, 2026 19:09

Alan J Hewitt (alanjhewitt) added this to the Autumn 2026 milestone Jul 16, 2026

Mohit Dalvi (mcdalvi) reviewed Jul 22, 2026

View reviewed changes

Alan J Hewitt (alanjhewitt) added 3 commits July 27, 2026 11:50

Mohit and Ian suggested change

858eb60

move to argument list to remove issues with box model build

410b150

For Mohit - Inline comments

8055d33

This was referenced Jul 29, 2026

Segmetation in calls from lfric_apps to radaer #21

Closed

Radaer seg - Currently parked to work on radaer api MetOffice/lfric_apps#191

Open


		USE ukca_radaer_prepare_mod, ONLY: ukca_radaer_prepare

		USE um_physics_init_mod, ONLY: n_radaer_mode

		CHARACTER(LEN=*), PARAMETER, PRIVATE :: ModuleName = 'UKCA_RADAER_LFRIC_API_MOD'

		CONTAINS

		IF (lhook) CALL dr_hook(ModuleName//':'//RoutineName, zhook_in, zhook_handle)

		!-----------------------------------------------------------------------

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Alan J Hewitt (alanjhewitt) commented Jul 16, 2026 • edited by mcdalvi Loading Uh oh! There was an error while loading. Please reload this page.

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PR Summary

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Mohit Dalvi (mcdalvi) commented Jul 29, 2026

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Alan J Hewitt (alanjhewitt) commented Jul 16, 2026 •

edited by mcdalvi

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