61 extracting inferno hardwired flammability params

[Eleanor Burke (eleanorgb)]

PR Summary

issue: [https://github.com//issues/61]

[https://github.com/MetOffice/um/pull/131]

test branch: https://github.com/eleanorgb/jules/tree/test_61-extracting-inferno-hardwired-flammability-params

Sci/Tech Reviewer: chantelleburton
Code Reviewer: Pierre Siddall (@Pierre-siddall)

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 understanding and enhance the readability of the code
• My changes generate no new warnings
• If editing rose-meta/jules-shared then have you supplied a linked UM and LFRic Apps PR?

Testing

• I have tested this change locally, using the JULES 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.)

Test Suite Results - jules - inferno/run1

Suite Information

Item	Value
Suite Name	inferno/run1
Suite User	eleanor.burke
Workflow Start	2026-09-15T08:25:17
Groups Run	all

Dependency	Reference	Main Like
jules	eleanorgb/jules@test_61-extracting-inferno-hardwired-flammability-params	False
SimSys_Scripts	MetOffice/SimSys_Scripts@2026.07.1	True

Task Information

✅ succeeded tasks - 676

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

Approvals

Please request all relevant approvals. See the CodeOwners.txt file for section owners.

Technical

• JULES Code Owner
• OpenMP
• River Routing
• Rose Stem
• Rose Metadata
• Upgrade Macros

Scientific

• Surface
• Hydrology
• Vegetation
• Veg3 RED Demography
• Biogeochemistry
• Biogenic fluxes
• Fire
• Lakes
• Evaluation
• Imogen

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
• 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

[Copilot]

Pull request overview

This PR restructures JULES fire-related configuration by introducing a dedicated jules_inferno namelist (and module) for INFERNO/TRIFFID fire parameters, while also refactoring several standalone/ancillary routines into proper Fortran modules and tightening some CI/workflow configuration.

Changes:

• Added jules_inferno_mod and migrated INFERNO/TRIFFID fire switches and parameters (e.g., l_inferno, l_trif_fire, z_burn_max, combustion completeness bounds, and new flammability tunables) out of other modules/namelists.
• Added a new PFT parameter fireveg_c_to_atmos(_io) and updated TRIFFID to use it for fire carbon-to-atmosphere partitioning.

[Copilot]

Pull request overview

Copilot reviewed 81 out of 89 changed files in this pull request and generated 2 comments.

Suppressed comments (7)

src/control/shared/jules_inferno_mod.F90:118

• errorstatus is not initialised before being passed to ereport in most branches (it is only assigned when ignition_method is invalid). This can cause inconsistent or silent error handling depending on the compiler/runtime state.
  src/control/shared/jules_inferno_mod.F90:129
• flam_sm_func is used as a selector in calc_flam, but the namelist checker does not validate it. If a user sets an unexpected value, calc_flam can use an uninitialised f_sm_l.
  src/science/fire/inferno/inferno_mod.F90:252
• l_cf_old_inferno is hard-coded to .TRUE., which means the new jules_inferno namelist parameters (flam_*) are effectively ignored (relative humidity bounds and flam_rain_const are overridden). This defeats the purpose of extracting these parameters for tuning.
  src/science/fire/inferno/inferno_mod.F90:295
• The new rainfall scaling branch applies EXP(-flam_rain_const * rain_l), but check_jules_inferno requires flam_rain_const <= 0.0. With the leading minus this makes rainfall increase flammability and can overflow. The exponent should be consistent with the sign convention and should use a clearly defined rain unit.
  src/science/fire/inferno/inferno_io_mod.F90:320
• Fuel normalisation is still hard-coded to 0.02/0.2, so the extracted flam_fuel_low/flam_fuel_up tunables are not actually used.
  rose-meta/jules-standalone/versions.py:99
• The upgrade macro sets flam_rhum_low/flam_rhum_up to 0.1/0.9, but the model computes relative humidity in percent (0–100) and check_jules_inferno expects 0–100. This would drastically change behaviour for upgraded apps.

        self.add_setting(config, ["namelist:jules_inferno", "flam_rhum_low"], "0.1")
        self.add_setting(config, ["namelist:jules_inferno", "flam_rhum_up"], "0.9")

doc/source/namelists/fire.nml.rst:169

• The literal word "buggy" in the namelist documentation looks like a placeholder and will ship to users.

buggy

[Copilot]

Pull request overview

Copilot reviewed 32 out of 34 changed files in this pull request and generated 8 comments.

Suppressed comments (2)

src/control/shared/jules_inferno_mod.F90:479

• The standalone namelist-open failure message duplicates the same phrase twice, which makes the error noisy and harder to read.

IF ( ERROR /= 0 )                                                              &
  CALL log_fatal("init_inferno", "Error opening namelist file fire.nml " //    &
                 "Error opening namelist file fire.nml " //                    &
                 "(IOSTAT=" // TRIM(to_string(ERROR)) // " IOMSG=" //          &
                 TRIM(iomessage) // ")")

rose-meta/jules-shared/jules-inferno/HEAD/rose-meta.conf:63

• flam_sm_low is described as a fraction of saturation (0–1) in code/docs, but rose metadata allows up to 10.0 here. This inconsistency can lead to invalid configurations being accepted by rose but rejected at runtime.

url=https://metoffice.github.io/jules/latest/namelists/jules_inferno.nml.html#JULES_INFERNO::flam_rain_const

[Copilot]

🟡 Changes recommended

There are confirmed functional issues (inverted z_burn_max missing-value check, calc_flam not correctly applying the new rainfall scaling parameter, and rose-stem JSON pointing at a non-existent source path) that would break configurations/builds.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

Suppressed comments (5)

Previously missed (1) — in code that hasn't changed since the last review.

src/initialisation/standalone/init_inferno_mod.F90:39

• init_inferno_mod redefines ignition_method option constants locally even though they already exist in jules_inferno_mod. Duplicating these values risks drift if they ever change; import the parameters from jules_inferno_mod instead.

src/science/fire/inferno/inferno_mod.F90:239

• calc_flam still hardcodes the rainfall scaling via cr=-2.0*s_in_day, which makes the new flam_rain_const argument effectively unused and keeps the historical double conversion behaviour. Removing cr here avoids having an unused/duplicated constant and ensures rainfall scaling is controlled via the namelist parameter.
  doc/source/namelists/fire.nml.rst:201
• Typo in documentation: "completness" should be "completeness".

   Maximum DPM soil carbon pool combustion completness fraction.

doc/source/namelists/fire.nml.rst:208

• Typo in documentation: "completness" should be "completeness".

   Minimum RPM soil carbon pool combustion completness fraction.

src/science/fire/inferno/inferno_mod.F90:284

• flam_rain_const is passed into calc_flam but is not applied in the flammability rainfall term; instead a hardwired constant is used after converting rain to mm/day. This prevents tuning/removing the rainfall dependence via the new namelist and is inconsistent with the new interface.

• Files reviewed: 33/35 changed files
• Comments generated: 4
• Review effort level: Lite

[Copilot]

🟡 Changes recommended

There are confirmed functional issues (e.g., flam_rain_const not being applied in calc_flam, and Rose-stem JSON referencing a non-existent fire module path) that would prevent correct behavior and/or successful builds.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

Suppressed comments (5)

Previously missed (1) — in code that hasn't changed since the last review.

rose-meta/jules-shared/jules-inferno/HEAD/rose-meta.conf:44

• The Rose metadata range for flam_fuel_low has no upper bound, but check_jules_inferno enforces flam_fuel_up <= 1.0 and the code treats fuel as a 0–1 normalised quantity. The metadata range should match the implemented constraints to prevent users configuring values that will always error at runtime.

This issue also appears on line 49 of the same file.

src/science/fire/inferno/inferno_mod.F90:284

• flam_rain_const is passed into calc_flam but never used; rainfall scaling still uses the hard-coded cr and a converted rain_rate. This means the new jules_inferno namelist cannot tune the rainfall–flammability relationship as intended (and the legacy/double-conversion behavior described in the docs cannot be reproduced via flam_rain_const).
  src/science/fire/inferno/inferno_mod.F90:277
• If flam_sm_func is ever set to an unexpected value, f_sm_l is left uninitialised before being used in the flam_l calculation. Even though check_jules_inferno validates values when l_inferno=T, guarding here avoids undefined behavior if this routine is called before checks or from another code path.
  src/control/shared/jules_inferno_mod.F90:184
• flam_fuel_up is allowed to equal flam_fuel_low here, but inferno_io_mod divides by (flam_fuel_up - flam_fuel_low) when normalising fuel, which would be a divide-by-zero. Make the check strict (<=) to prevent invalid configurations.

  IF ( ABS(flam_fuel_up - rmdi) < EPSILON(rmdi) ) THEN
    CALL ereport( TRIM(RoutineName), errorstatus,                              &
                "flam_fuel_up needs to be specified.")
  ELSE IF ( flam_fuel_up < flam_fuel_low ) THEN
    CALL ereport( TRIM(RoutineName), errorstatus,                              &
                "flam_fuel_up must be > flam_fuel_low")

rose-meta/jules-shared/jules-inferno/HEAD/rose-meta.conf:55

• The Rose metadata range for flam_fuel_up has no upper bound, but check_jules_inferno enforces flam_fuel_up <= 1.0 and the code treats fuel as a 0–1 normalised quantity. The metadata range should match the implemented constraints to prevent users configuring values that will always error at runtime.

[namelist:jules_inferno=flam_fuel_up]
compulsory=true
description=Upper fuel load threshold for flammability
range=0.0:
sort-key=Panel-J13
type=real
url=https://metoffice.github.io/jules/latest/namelists/jules_inferno.nml.html#JULES_INFERNO::flam_fuel_up

• Files reviewed: 33/35 changed files
• Comments generated: 2
• Review effort level: Lite

[Copilot]

🟡 Changes recommended

INFERNO flammability rainfall scaling is still hard-coded (ignoring the new namelist parameter) and there are a few validation/doc inconsistencies that can lead to incorrect behaviour or confusion.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

Suppressed comments (8)

Previously missed (4) — in code that hasn't changed since the last review.

src/science/fire/inferno/inferno_mod.F90:276

• f_sm_l is not assigned if flam_sm_func is not 1 or 2, but it is still used in the flammability calculation; this can lead to undefined results if the routine is ever called with an unexpected value.
  src/control/shared/jules_inferno_mod.F90:148
• The error message for flam_rhum_up says it must be ">= flam_rhum_low", but the code rejects equality (<=) and equality would also cause a divide-by-zero in calc_flam. The message should match the actual constraint (strictly greater).
  doc/source/namelists/fire.nml.rst:70
• The JULES_INFERNO section is missing a .. nml:namelist:: JULES_INFERNO directive, and it references l_trif_fire/l_inferno as members of JULES_INFERNO, but those switches are in the JULES_VEGETATION namelist.
  src/control/shared/jules_inferno_mod.F90:201
• The ccdpm_max bounds check allows a value of exactly 1.0 (> 1.0 is rejected), but the error message says "must be < 1.0". This is misleading for users.

This issue also appears on line 217 of the same file.

src/science/fire/inferno/inferno_mod.F90:284

• flam_rain_const is passed into calc_flam but not used; the rainfall term still uses the hard-coded constant cr, so changing the namelist parameter has no effect (and the upgrade macro/doc value will be ignored).
  src/control/shared/jules_inferno_mod.F90:167
• The flam_fuel_up validation allows flam_fuel_up == flam_fuel_low, but inferno_io_mod divides by (flam_fuel_up - flam_fuel_low); equality will cause a divide-by-zero.

  ELSE IF ( flam_fuel_up < flam_fuel_low ) THEN
    CALL ereport( TRIM(RoutineName), errorstatus,                              &
                "flam_fuel_up must be > flam_fuel_low")

src/control/shared/jules_inferno_mod.F90:220

• The ccrpm_max bounds check allows a value of exactly 1.0 (> 1.0 is rejected), but the error message says "must be < 1.0". This is misleading for users.

  ELSE IF ( ccrpm_max > 1.0 ) THEN
    CALL ereport( TRIM(RoutineName), errorstatus,                              &
                "ccrpm_max must be < 1.0.")
  END IF

src/control/shared/jules_inferno_mod.F90:55

• Typo in the ccrpm_min comment: "urn fraction" should be "burn fraction".

  ccrpm_min = rmdi,                                                            &
    ! Minimum resistant plant material urn fraction (0 <= fraction <= 1)
  ccrpm_max = rmdi,                                                            &

• Files reviewed: 25/27 changed files
• Comments generated: 2
• Review effort level: Lite