Minutes of the code management group meeting 2026-05-14

Code management group minutes

Teleconference Details

Thursday 14th May 2026, 10.00am - 11.30am GMT

Meeting via Teams - see link in calendar invitation

Met Office: MS, MD, AJH, PMJ, JCK,

Cambridge: LA, RW

Leeds: DG

Canterbury: CH

CSIRO:

Apologies:

NEXT MEETING WILL BE THURSDAY 9TH JULY 2026, 10.00-11.30 GMT

Actions from this meeting

(ongoing) GM/DG to update table on UKCA wiki documenting GLOMAP versions. DG/GM to consider the code and lodging process for GLOMAP developments and consider a suitable rose-stem test supported by NLA. GM Will work with DG to get a subset to commit. AJH to review. Graham has found code needed for meteoric smoke. Coding needed to get changes in. Have a way forward.
(ongoing) AJH on update API document to UM13.6 release. NLA to provide feedback before it is be circulated. There is a comprehensive overhaul for 13.7. AJH to make document available for wider information/comment - see here. AJH won't do anything with API until GitHub release is out, and then will add some things to it. AJH working on the RADAER API. Have made notes in a different document, and then will merge into single document. Expected around September.
(ongoing) ALL look at um:#6203 showing other unprotected rose-stem options and think about any code/settings they are interested in. May be able to use GitHub actions.
(ongoing) ALL to consider ordering of the Progress with Priorities table and highlight things that should be higher priority, and any other tasks that need to be included.
(ongoing) NLA / MD to put a link to Monsoon3 guide to GitHub in the minutes
(ongoing) MD is developing workaround for Bug in Lfric copy of ukca_volcanic_so2. However, this will not add functionality in lfric. A developer for this needs to be identified. Lodged in LFRic, confirmed with May Chim and is happy to do for UM, but may have issues with testing
(ongoing) AJH to tidy up the priority table. Some items are now complete and should be marked as such.
(ongoing) AJH, MD, and PMJ to discuss method for checking diagnostic KGOs with NetCDF files.

Actions from the Last Meeting

(ongoing) GM/DG to update table on UKCA wiki documenting GLOMAP versions. DG/GM to consider the code and lodging process for GLOMAP developments and consider a suitable rose-stem test supported by NLA. GM Will work with DG to get a subset to commit. AJH to review. Graham has found code needed for meteoric smoke.
- Coding needed to get changes in. Have a way forward.
(ongoing) AJH on update API document to UM13.6 release. NLA to provide feedback before it is be circulated. There is a comprehensive overhaul for 13.7. AJH to make document available for wider information/comment - see here. AJH won't do anything with API until GitHub release is out, and then will add some things to it.
- AJH working on the RADAER API. Have made notes in a different document, and then will merge into single document. Expected around September
(ongoing) ALL look at um:#6203 showing other unprotected rose-stem options and think about any code/settings they are interested in. May be able to use GitHub actions.
- Ongoing
(ongoing) ALL to consider ordering of the Progress with Priorities table and highlight things that should be higher priority, and any other tasks that need to be included.
- Ongoing
(this happened - not sure if follow up is required) NLA to mention MASS issues at the next MMG
- Waiting for new MASS
(new) NLA / MD to put a link to Monsoon3 guide to GitHub in the minutes
- Ongoing
(new) AJH to request UKCA tags for lfric_apps and UM , so that we are able to keep track of all UKCA GitHub pull requests and issues at the next CMG meeting.
- Closed - done
(new) MD is developing workaround for Bug in Lfric copy of ukca_volcanic_so2. However, this will not add functionality in lfric. A developer for this needs to be identified.
- Lodged in LFRic, confirmed with May Chim and is happy to do for UM, but may have issues with testing
(new) AJH has contacted the LFRic core team to inform them of the obsolete instructions for building lfric core with FCM.
- There may be an automated system for making instructions.
- Closed
(new) AJH to tidy up the priority table. Some items are now complete and should be marked as such.
- Ongoing
(new) AJH and Pedro to discuss method for checking diagnostic KGOs with NetCDF files.
- AJH, MD, PMJ to catch-up offline
- ongoing

Issues/PRs

REMEMBER TO LINK UKCA IN YOUR UM AND LFRIC_APPS (& OTHER REPO) ISSUES/PRs

Generally, people have found GitHub OK to work with, but found trac easier to navigate.

Need to be on reviewers list to be able to make edits to other PRs and also add links. AJH to contact SSD team. May be due to UKCA being BSD-3 and open source. Could perhaps make a change to the CONTRIBUTORS.md and then add people to be able to edit once that has been done.

Issues

Pull Requests

Progress with Priorities (NLA)

ACTION REQUEST FROM UKCA SCIENCE & MANAGEMENT BOARD: CMG to provide list of priorities & their status, with particular thought to UKESM2 changes that will be required.

Progress with Priorities table

Bugs/Bugfixes (NLA)

Open Bugs

#	Description	Ticket	Owner	Comments	Comments from this meeting
124	H2 and N2 cannot be set for RCP and WMOA1 scenario routines	UM:#5620 vn13.8.1_ukca_rcp_read_h2_n2	Mohit	Values are hard-wired in the code and cannot be changed without a branch. N2 values seem to be read from namelist (for UM, and RCP scenarios). Branch adds possibility to read H2 from either RCP or namelist. Will probably require updating all UKCA-chem apps to maintain KGO. More testing required MD has done a little bit of work. N2 is read from namelist, but can now read from RCP file for H2
128	Bug in UKCA stratospheric chemistry diagnostics	UM:#5839	Luke Abraham	The indexing/values of diagnostics m01s50i101-i104 are incorrect. Fixes provided for vn11.1 and vn11.7. May affect CMIP6 diagnostics Does this need fixing for CMIP7? Need to discuss with CDDS/diagnostics team as might break existing workflow.
143	Error in print statements from UKCA_TRACERS_COPY_FROM_UM	Not yet	???	The final species listed in the diagnostic print statement seems to have very large concentrations (O(1E+08)) compared to others in the ppm-ppt range. Does not seem to affect model output. Reported by James Weber.
144	interchangeable use of specific humidity and water vapour mixing ratio	#6813	John Hemmings and ???	UKCA includes calculations of relative humidity, clear-sky relative humidity and saturation vapour pressure. Relative humidity calculations should be based on water vapour mass mixing ratio but are in part based on specific humidity. Also, the calculation of saturation vapour pressure is derived from saturation mixing ratio but uses a formula for deriving SVP from saturation specific humidity. This interchangeable use of specific humidity (ratio for moist air) and mixing ratio (ratio for dry air) in existing configurations introduces small numerical errors in UM and LFRic model runs. These bugs were identified at UM version vn12.2 and have been highlighted by comments in code lodged with UM ticket #6660 (in ukca_main1-ukca_main1.F90 and atmos_ukca_humidity_mod.F90). All UKCA configurations are affected. Alan - This should be fixed by Met Office. I will speak with Anthony and Alistair about resourcing to fix this. It requires good understanding of humidity to work through this problem, otherwise I would have done this myself. When we pass stuff through the argument list, the name changes which makes things complicated. Should we pass a structure with all the humidity fields in? There is a UKCA bespoke version of humidity calculations for non-UM applications. Internal Met Office problem - will need to find someone to fix it. AJH to talk with AJ and Alistair Sellar. GM can cross-check. Ticket has 2 parts. JH suggests doing it in 2 tickets, 1 technical, 1 bug fix. JH could do technical part (either as callback routines or separate fields). Then would need UM & LFRic tickets for the bug fix, as calculations could be done in the parent or as callback routine. Some work has been done - technical change has been done in ukca:#245. Went in at UM13.9. This option is now used by the UM and LFRic. Buggy calculations are now outside of UKCA - will require UM and LFRic changes to fix those. Might not be a large amount of work, but problem needs to be well understood. Also consider what field is being passed in the tracer list - currently q but should be mixing ratio. Some has been fixed - bug has been shifted outside of UKCA. Don't know of anyone working on it currently. Someone will need to go through and check we are passing the correct one - need someone on aerosol side and on chemistry side Also has problems with GLOMAP-clim
153	bug in 2D photolysis			While working on developments for the new photolysis API, we’ve noticed a likely error in the current implementation of the 2D photolysis. The 2D photolysis files are tabulated by day of year at 5-day resolution, amongst other variables. The interpolation to the actual day of year is currently done in the read subroutine (read2d_opt or read2d_orig). However, this subroutine is only called once on the first timestep. For multi-day runs, the photolysis rates will not be updated as the day of year increases. Since nobody is using the 2D photolysis at the moment this is likely of low to no impact. Might be used by NUAQ BD or VB will know more - PMJ will ask
154	bug in tropospheric heterogeneous chemistry			Within GLOMAP the `wetdp` variable is defined as the wet diameter in m. However, in `ukca_trop_hetchem` this is used as a radius in cm. This results in a factor of 50x error. Steve Turnock might be using this. NLA to contact ST and YG about this.
155	OMP dynamic scheduling race condition	ukca:#321		When using OpenMP with dynamic, as opposed to the standard static, scheduling, checksums were failing with lfric_apps. This indicates a race condition likely within the ASAD chemical package and so would affect the UM as well as LFRic. Further testing is needed. AJH will make some time to run it with the thread santizer	RW to double-check notes - bug we introduced. Can be closed. Need LFRic tests with dynamic scheduling.
156	Bug in Lfric copy of ukca_volcanic_so2, `true_latitude, true_longitude` used without allocating. Fails on ARCHER2 with CCE compiler	lfric_apps:PR133	Mohit Dalvi	Since lfric_apps-vn2.2 Temporarily allocate true-latitude, true_longitude, weight_volc_vertdist lfric_apps:#965 removed UM dependencies i.e. trignometric_mod without providing alternative source for the arrays	Fixed in LFRic, CLOSE - UM below.
157	Bug in calculation of aerosol AOD from LFRic	FCM lfric_apps:#1089 GitHub lfric_apps:#41	Alan J Hewitt	Since lfric vn2.2 FCM git_migration_AOD_bug Github AOD_bug aerosol AOD was developed in lfric_apps:#440 and it looked fine at low resolution. Running at high resolution identified an addressing error. Fix has been developed and will be in review for Jan 2026 deadline.	Closed
158	While analysing #156, it was noticed that in the UM version of `ukca_volcanic_SO2` the array weight_volc_vertdist is being populated without being allocated.		May Chim?	Since UM vn13.9 Needs to be allocated as weight_volc_vertdist(l2-l1+1) and deallocated in each iteration over nreupt
159	Logical l_ukca_prescribech4 should not be active in Strat schemes			In ukca_add_emiss the logical enables overwriting of CH4 surface values with prescribed concentrations. However, later on in the routine this action is repeated in a section specific to 'Strat' schemes, where use of prescribed vs emitted CH4 is governed by l_ukca_emisdrvn_ch4, thus over-ridding the first logical. Since UM vn11.x Should be turned Off in rose metadata for Strat schemes
160	Mismatch in tracer names indexing across UKCA API.			Could be related to #143. Printing from UKCA_TRACER_COPY_TO/FROM_UM, and comparing all_tracers_names vs tr_names shows misalignment in names of species. Note: this may be just limited to the population of tr_names array as any actual misalignment would have been noticed for radiative feedback as well as tracers/ diagnostics in output Since UM vn10.6?

DG - small bug in STASH diagnostics at chem version 132

Redundant Code (NLA)

Code for deletion

PLEASE REMEMBER TO EDIT THE ORIGINAL REDUNDANT CODE TABLE AND NOT THIS PAGE

PMJ - looking to send full domain and use ASAD/NR for RAQ, but taking time. Want to be able to use parallelisations there.

Desirable Science not tested

PLEASE REMEMBER TO EDIT THE ORIGINAL SCIENCE NOT TESTED TABLE AND NOT THIS PAGE

See also the complete list of unprotected rose-stem options

#	Description	Remarks	Owner
1	Use of tropospheric (2D) look-up table photolysis	Still useful to compare against FastJX. May be used for a "fast" configuration. Will be doen as part of photolysis refactoring
2	TropIsop chemistry configuration	May be useful in a "fast" configuration & to drive GLOMAP-mode. Useful for low-top configurations.
3	Strat chemistry configuration	Useful for stratospheric studies, particularly with a high model top.	Luke Abraham

AJH hasn't got microplastics rose-stem test working yet, will make time later. Is not sure what is going on. CH can provide input on that.

Round (virtual) Table of current activities, plans

Person	Activity
NLA	NLA & RW are submitting to SSI RSMF for the Box Model
AJH	LFRic PS49 milestone including aerosols (GLOMAP), deadline is Summer 2027. Lots of different groups now interested. Might be aiming to turn off the UM at the start of 2028.

A.O.B. & D.N.M. (NLA)

DG - UKCA meeting in July.