Add logical to allow for the fixing the duplicate heterogeneous chemistry reactions in UKCA StratTrop and CRI-Strat2 schemes

CONTRIBUTORS.md

@@ -34,4 +34,5 @@
 | thomasmelvin        | Thomas Melvin      | Met Office                       | 2026-01-15 |
 | tinyendian          | Wolfgang Hayek     | Earth Sciences New Zealand       | 2026-02-02 |
 | DanStoneMO          | Daniel Stone       | Met Office                       | 2026-02-26 |
-| ericaneininger      | Erica Neininger    | Met Office                       | 2026-03-02 |
+| ericaneininger      | Erica Neininger    | Met Office                       | 2026-03-02 |
+| theabro             | Nathan Luke Abraham | NCAS & University of Cambridge  | 2026-04-15 |

dependencies.yaml

@@ -50,5 +50,5 @@ socrates-spectral:
     ref: 2026.03.2
 
 ukca:
-    source: git@github.com:MetOffice/ukca.git
-    ref: 2026.03.2
+    source: git@github.com:theabro/ukca.git
+    ref: um14.1_hetchem_fixes

interfaces/physics_schemes_interface/source/legacy/misc/science_fixes_mod.F90

@@ -92,6 +92,8 @@ module science_fixes_mod
 logical :: l_fix_neg_pvol_wat = .false.    ! Review in Jan 2020
 ! ticket #3245
 logical :: l_fix_ukca_h2so4_ystore = .false. ! Review Oct 2020
+! issue #432, ukca#30
+logical :: l_fix_ukca_n2o5_h2o = .false. ! Review June 2028
 ! ticket #4501
 logical :: l_fix_pc2_cnv_mix_phase = .false. ! Review Dec 2021
 ! ticket #5031
@@ -149,7 +151,7 @@ module science_fixes_mod
         l_fix_improve_drydep, l_fix_drydep_so2_water,                          &
         l_fix_ukca_h2dd_x, l_fix_neg_pvol_wat,                                 &
         l_fix_pc2_cnv_mix_phase,                                               &
-        l_fix_ukca_h2so4_ystore, l_fix_tidy_rainfracs,                         &
+        l_fix_ukca_h2so4_ystore, l_fix_ukca_n2o5_h2o, l_fix_tidy_rainfracs,    &
         l_fix_incloud_qcf, l_fix_mcr_frac_ice,                                 &
         l_fix_ukca_offox_h2o_fac, l_fix_ukca_cloud_frac, l_fix_gr_autoc,       &
         l_fix_ukca_activate_vert_rep, l_fix_ukca_activate_pdf,                 &
@@ -475,6 +477,15 @@ subroutine warn_temp_fixes()
   call ereport(RoutineName, ErrorStatus, CMessage)
 end if
 
+if (.not. l_fix_ukca_n2o5_h2o) then
+  ErrorStatus = -100
+  cmessage    =                                                       newline//&
+  'model run excludes a change from issue #432, ukca#30 as'//         newline//&
+  ' l_fix_ukca_n2o5_h2o=.false. .'//                                  newline//&
+  ' this will disable stratflag n2o5+h2o filtering for b85 and h04 reactions.'
+  call ereport(RoutineName, ErrorStatus, CMessage)
+end if
+
 if (.not. l_fix_pc2_cnv_mix_phase ) then
   ErrorStatus = -100
   cmessage    =                                                       newline//&
@@ -756,6 +767,9 @@ subroutine print_nlist_temp_fixes()
 write(lineBuffer,'(A,L1)') 'l_fix_ukca_h2so4_ystore',                          &
                             l_fix_ukca_h2so4_ystore
 call umPrint(lineBuffer,src=ModuleName)
+write(lineBuffer,'(A,L1)') 'l_fix_ukca_n2o5_h2o',                              &
+                            l_fix_ukca_n2o5_h2o
+call umPrint(lineBuffer,src=ModuleName)
 write(lineBuffer,'(A,L1)') ' l_fix_pc2_cnv_mix_phase = ',                      &
                              l_fix_pc2_cnv_mix_phase
 call umPrint(lineBuffer,src=ModuleName)

interfaces/physics_schemes_interface/source/support/um_ukca_init_mod.f90

@@ -1057,6 +1057,7 @@ subroutine ukca_init( row_length, rows, model_levels, bl_levels,             &
            proc_bl_tracer_mix = bl_tracer_mix,                                 &
            ! UKCA temporary logicals
            l_fix_ukca_hygroscopicities=.false.,                                &
+           l_fix_ukca_n2o5_h2o=.false.,                                        &
            l_fix_ukca_water_content=.true.,                                    &
            ! Return status information
            error_message=ukca_errmsg,                                          &