cam6_4_195: Aerosol surface area densities refactor

bld/build-namelist

@@ -3898,6 +3898,34 @@ if ($chem =~ /_mam(\d)/) {
     }
 }
 
+# SAD process participation spec_types
+if ($chem =~ /_mam/) {
+    add_default($nl, 'sad_chem_spec_types',
+       'val'=>"'sulfate','s-organic','p-organic','black-c','ammonium'");
+    # sad_seasalt_spec_types is MAM-only: CARMA does not compute separate
+    # sea-salt SAD (its aero_model_surfarea sets sad_ssa to a sentinel value).
+    add_default($nl, 'sad_seasalt_spec_types',
+       'val'=>"'seasalt'");
+    # b4b default matches sad_chem_spec_types; mo_sad.F90 currently assumes
+    # all strat SAD is sulfate aerosol (see sad_strat_calc/sulfate_sad_calc).
+    add_default($nl, 'sad_strat_spec_types',
+       'val'=>"'sulfate','s-organic','p-organic','black-c','ammonium'");
+}
+if ($carma ne 'none' and $chem !~ /_mam/) {
+    add_default($nl, 'sad_chem_spec_types',
+       'val'=>"'sulfate','s-organic','p-organic','black-c','ammonium'");
+    # b4b default matches sad_chem_spec_types; mo_sad.F90 currently assumes
+    # all strat SAD is sulfate aerosol (see sad_strat_calc/sulfate_sad_calc).
+    add_default($nl, 'sad_strat_spec_types',
+       'val'=>"'sulfate','s-organic','p-organic','black-c','ammonium'");
+}
+if ($aer_model eq 'bam' and $prescribed_aero_model eq 'none') {
+    add_default($nl, 'sad_chem_spec_types',
+       'val'=>"'sulfate','black-c','p-organic','s-organic','nitrate'");
+}
+# ...for prescribed BAM with chemistry (WACCM-4) sad_chem_spec_types should
+# be empty as sulfate is from supplemental SAD from sulf_file, not here.
+
 # Gravity wave drag settings
 
 # By default, orographic waves are always on

bld/namelist_files/namelist_definition.xml

@@ -6784,6 +6784,43 @@ Tuning for seasalt_emis
 Default: set by build-namelist.
 </entry>
 
+<entry id="sad_chem_spec_types" type="char*32(16)" category="cam_chem"
+       group="aerosol_nl" valid_values="" >
+Species types contributing to chemistry-relevant surface area density (SAD)
+for heterogeneous reaction rates. The SAD determines how much aerosol surface
+is available for gas-phase chemical reactions (computed in aero_model, used
+by mo_usrrxt).
+
+In bulk (BAM) configurations, types not in rad_climate are provided by
+a supplemental path in aero_model_surfarea.
+
+Default: 'sulfate','s-organic','p-organic','black-c','ammonium' (MAM, CARMA);
+'sulfate','black-c','p-organic','s-organic','nitrate' (prognostic bulk);
+UNSET (prescribed bulk)
+</entry>
+
+<entry id="sad_seasalt_spec_types" type="char*32(16)" category="cam_chem"
+       group="aerosol_nl" valid_values="" >
+Species types contributing to sea-salt surface area density (SAD).
+Computed separately from chemistry SAD and used for sea-salt-specific
+heterogeneous reactions.
+Default: 'seasalt'
+</entry>
+
+<entry id="sad_strat_spec_types" type="char*32(16)" category="cam_chem"
+       group="aerosol_nl" valid_values="" >
+Species types contributing to stratospheric surface area density (SAD).
+Used by aero_model_strat_surfarea to compute strato_sad, which is passed
+to sad_strat_calc (mo_sad.F90) for STS/NAT/ICE thermodynamic partitioning.
+Note: sad_strat_calc currently assumes all incoming SAD is sulfate aerosol
+(via sulfate_sad_calc and calc_radius_lbs). Supporting non-sulfate species
+in the stratospheric SAD pathway requires refactoring mo_sad.F90 to handle
+multiple aerosol types independently. The physically correct default would
+be 'sulfate' only, but the current default matches sad_chem_spec_types for
+bit-for-bit consistency with prior hardcoded behavior.
+Default: 'sulfate','s-organic','p-organic','black-c','ammonium'
+</entry>
+
 <entry id="aer_sol_facti" type="real(1000)" category="cam_chem"
        group="aerosol_nl" valid_values="" >
 In-cloud solubility factor used in BULK aerosol wet removal

doc/ChangeLog

@@ -1,5 +1,193 @@
 ===============================================================
 
+Tag name: cam6_4_195
+Originator(s): fvitt, jimmielin
+Date: 8 Aug 2026
+One-line Summary: Refactor aerosol surface area densities
+Github PR URL: https://github.com/ESCOMP/CAM/pull/1628
+
+Purpose of changes (include the issue number and title text for each relevant GitHub issue):
+
+ Aerosol surface area densities abstraction
+ #1625
+
+Describe any changes made to build system: N/A
+
+Describe any changes made to the namelist:
+
+ New namelist parameters:
+
+ sad_chem_spec_types
+  Species types contributing to chemistry-relevant surface area density (SAD)
+  for heterogeneous reaction rates. The SAD determines how much aerosol surface
+  is available for gas-phase chemical reactions (computed in aero_model, used
+  by mo_usrrxt).
+
+  In bulk (BAM) configurations, types not in rad_climate are provided by
+  a supplemental path in aero_model_surfarea.
+
+ sad_seasalt_spec_types
+  Species types contributing to sea-salt surface area density (SAD).
+  Computed separately from chemistry SAD and used for sea-salt-specific
+  heterogeneous reactions.
+
+ sad_strat_spec_types
+  Species types contributing to stratospheric surface area density (SAD).
+  Used by aero_model_strat_surfarea to compute strato_sad, which is passed
+  to sad_strat_calc (mo_sad.F90) for STS/NAT/ICE thermodynamic partitioning.
+  Note: sad_strat_calc currently assumes all incoming SAD is sulfate aerosol
+  (via sulfate_sad_calc and calc_radius_lbs). Supporting non-sulfate species
+  in the stratospheric SAD pathway requires refactoring mo_sad.F90 to handle
+  multiple aerosol types independently. The physically correct default would
+  be 'sulfate' only, but the current default matches sad_chem_spec_types for
+  bit-for-bit consistency with prior hardcoded behavior.
+
+List any changes to the defaults for the boundary datasets: N/A
+
+Describe any substantial timing or memory changes: N/A
+
+Code reviewed by: jimmielin
+
+List all files eliminated: N/A
+
+List all files added and what they do:
+A       src/chemistry/aerosol/aerosol_spec_utils.F90
+ - utility module for aerosol types in SAD calculations
+
+List all existing files that have been modified, and describe the changes:
+M       bld/build-namelist
+ - set defaults SAD types lists
+
+M       bld/namelist_files/namelist_definition.xml
+ -  SAD types lists
+
+M       src/chemistry/aerosol/aerosol_state_mod.F90
+M       src/chemistry/aerosol/bulk_aerosol_state_mod.F90
+M       src/chemistry/aerosol/carma_aerosol_state_mod.F90
+M       src/chemistry/aerosol/modal_aerosol_state_mod.F90
+ - new aero_surf_area routine
+
+M       src/chemistry/bulk_aero/aero_model.F90
+ - read SAD types list in namelist
+ - invoke aero_state%surf_area
+ - include supplemental SAD calcs for aerosols not included in rad_climate
+
+M       src/chemistry/carma_aero/aero_model.F90
+M       src/chemistry/modal_aero/aero_model.F90
+ - read SAD types list in namelist
+ - invoke aero_state%surf_area
+
+M       src/chemistry/mozart/mo_gas_phase_chemdr.F90
+M       src/chemistry/mozart/mo_usrrxt.F90
+ - clean up args for surf area routine
+
+M       src/chemistry/mozart/mo_sulf.F90
+ - move SULFATE hist outfld call to gas_phyase_chemdr
+
+If there were any failures reported from running test_driver.sh on any test
+platform, and checkin with these failures has been OK'd by the gatekeeper,
+then copy the lines from the td.*.status files for the failed tests to the
+appropriate machine below.  All failed tests must be justified.
+
+derecho/intel/aux_cam:
+  NLFAIL ERC_D_Ln9.f09_f09_mt232.FHIST_BDRD.derecho_intel.cam-outfrq9s
+  NLFAIL ERC_D_Ln9.f19_f19_mt232.QPC6.derecho_intel.cam-outfrq3s_cosp
+  NLFAIL ERC_D_Ln9.mpasa120_mpasa120.F2000climo.derecho_intel.cam-outfrq9s_mpasa120
+  NLFAIL ERC_D_Ln9.mpasa120_mpasa120.FHISTC_LTso.derecho_intel.cam-outfrq9s_mpasa120
+  NLFAIL ERC_D_Ln9.ne30pg3_ne30pg3_mt232.F1850C_LTso.derecho_intel.cam-outfrq9s
+  NLFAIL ERC_Ln9.C96_C96_mt232.F2000climo.derecho_intel.cam-outfrq9s
+  NLFAIL ERI_D_Ln18.f09_f09_mt232.FHIST.derecho_intel.cam-outfrq3s_eri
+  NLFAIL ERI_D_Ln18.f19_f19_mt232.FHIST_C5.derecho_intel.cam-outfrq3s_eri
+  NLFAIL ERI_D_Ln18.ne30pg3_ne30pg3_mt232.FHISTC_LTso.derecho_intel.cam-outfrq3s_eri
+  NLFAIL ERP_D_Ln9.ne30pg3_ne30pg3_mt232.F1850C_MTso.derecho_intel.cam-outfrq9s
+  NLFAIL ERP_D_Ln9_P64x2.f09_f09_mg17.QSC6.derecho_intel.cam-outfrq9s
+  NLFAIL ERP_Ld3.ne16pg3_ne16pg3_mg17.FHISTC_WAt1ma.derecho_intel.cam-reduced_hist1d
+  NLFAIL ERP_Ld3.ne30pg3_ne30pg3_mt232.FHISTC_MTt4s.derecho_intel.cam-outfrq1d_aoa
+  NLFAIL ERP_Ln9.f09_f09_mg17.FCSD_HCO.derecho_intel.cam-outfrq9s
+  NLFAIL ERP_Ln9.f19_f19_mg17.FWsc1850.derecho_intel.cam-outfrq9s
+  NLFAIL ERP_Ln9.ne30pg3_ne30pg3_mg17.FCnudged.derecho_intel.cam-outfrq9s
+  NLFAIL ERP_Ln9.ne30pg3_ne30pg3_mg17.FHISTC_WAma.derecho_intel.cam-outfrq9s
+  NLFAIL ERR_Ln9.ne16pg3_ne16pg3_mt232.FHISTC_LTso.derecho_intel.cam-outfrq9s_bwic
+  NLFAIL ERS_Ln9.f09_f09_mg17.FX2000.derecho_intel.cam-outfrq9s
+  NLFAIL ERS_Ln9.f19_f19_mg17.FXSD.derecho_intel.cam-outfrq9s
+  NLFAIL ERS_Ln9.ne30pg3_ne30pg3_mg17.FHISTC_WXma.derecho_intel.cam-outfrq9s_ctem
+  NLFAIL SCT_D_Ln7.ne3_ne3_mg37.QPC5.derecho_intel.cam-scm_prep
+  NLFAIL SMS_C2_D_Ln9.ne16pg3_ne16pg3_mg17.FHISTC_WXma.derecho_intel.cam-outfrq9s
+  NLFAIL SMS_D_Ld5.f09_f09_mt232.PC6.derecho_intel.cam-cam6_port_f09
+  NLFAIL SMS_D_Ln9.f09_f09_mg17.FCts2nudged.derecho_intel.cam-outfrq9s_leapday
+  NLFAIL SMS_D_Ln9.f09_f09_mg17.FCvbsxHIST.derecho_intel.cam-outfrq9s
+  NLFAIL SMS_D_Ln9.f09_f09_mg17.FSD.derecho_intel.cam-outfrq9s
+  NLFAIL SMS_D_Ln9.f19_f19_mg17.FCARMA2000climo.derecho_intel.cam-outfrq9s_carma_rad_diag
+  NLFAIL SMS_D_Ln9.f19_f19_mg17.FCHIST_SLH.derecho_intel.cam-outfrq9s
+  NLFAIL SMS_D_Ln9.f19_f19_mg17.FWma2000climo.derecho_intel.cam-outfrq9s
+  NLFAIL SMS_D_Ln9.f19_f19_mg17.FWma2000climo.derecho_intel.cam-outfrq9s_waccm_ma_mam4
+  NLFAIL SMS_D_Ln9.f19_f19_mg17.QPC2000climo.derecho_intel.cam-outfrq3s_usecase
+  NLFAIL SMS_D_Ln9.f19_f19_mt232.FHIST_C5.derecho_intel.cam-mam7
+  NLFAIL SMS_D_Ln9.ne0ARCTICne30x4_ne0ARCTICne30x4_mt12.FHIST.derecho_intel.cam-outfrq9s
+  NLFAIL SMS_D_Ln9.ne30pg3_ne30pg3_mt232.1850_CAM70%MT%CT4S2_CLM60%SP_CICE%PRES_DOCN%DOM_MOSART_SGLC_SWAV_SESP.derecho_intel.cam-outfrq9s
+  NLFAIL SMS_D_Ln9.ne30pg3_ne30pg3_mt232.FHISTC_MTso.derecho_intel.cam-outfrq9s
+  NLFAIL SMS_D_Ln9_P1280x1.ne30pg3_ne30pg3_mt232.FHISTC_MTt1s.derecho_intel.cam-outfrq9s_Leung_dust
+  NLFAIL SMS_D_Ln9_P1536x1.ne0CONUSne30x8_ne0CONUSne30x8_mt12.FCHIST.derecho_intel.cam-outfrq9s
+  NLFAIL SMS_Ld1.f09_f09_mg17.FCHIST_GC.derecho_intel.cam-outfrq1d
+  NLFAIL SMS_Ld1.f09_f09_mg17.FW2000climo.derecho_intel.cam-outfrq1d
+  NLFAIL SMS_Ld1.ne30pg3_ne30pg3_mg17.FC2010climo.derecho_intel.cam-outfrq1d
+  NLFAIL SMS_Lh12.f09_f09_mg17.FCSD_HCO.derecho_intel.cam-outfrq3h
+  NLFAIL SMS_Ln9.f09_f09_mg17.F2010climo.derecho_intel.cam-nudging
+  NLFAIL SMS_Ln9.f09_f09_mg17.FW1850.derecho_intel.cam-reduced_hist3s
+  NLFAIL SMS_Ln9.f19_f19_mt232.F2000climo.derecho_intel.cam-silhs
+  NLFAIL SMS_Ln9.ne30pg3_ne30pg3_mg17.FW2000climo.derecho_intel.cam-outfrq9s_rrtmgp
+   - new SAD species types lists
+
+  DIFF ERC_D_Ln9.f19_f19_mg17.QPMOZ.derecho_intel.cam-outfrq3s
+   - expected baseline failure due to BAM SAD refactor
+
+derecho/nvhpc/aux_cam:
+  FAIL ERS_Ln9.ne30pg3_ne30pg3_mt232.FHISTC_LTso.derecho_nvhpc.cam-outfrq9s_gpu_default MODEL_BUILD time=0
+   - pre-existing failure as of cam6_4_193
+
+izumi/nag/aux_cam:
+  FAIL ERC_D_Ln9.f10_f10_mt232.FHIST_C5.izumi_nag.cam-outfrq3s_subcol COMPARE_base_rest
+   - pre-existing failure -- see https://github.com/ESCOMP/CAM/issues/1514
+
+  NLFAIL ERC_D_Ln27.ne3pg3_ne3pg3_mt232.FKESSLER.izumi_nag.cam-outfrq9s
+  NLFAIL ERC_D_Ln9.f10_f10_mg37.QPWmaC6.izumi_nag.cam-outfrq9s_tuvx_waccm_ma_mam5
+  NLFAIL ERC_D_Ln9.f10_f10_mt232.FHIST.izumi_nag.cam-outfrq3s_cospsathist
+  NLFAIL ERC_D_Ln9.mpasa480_mpasa480_mt232.FHS94.izumi_nag.cam-outfrq9s
+  NLFAIL ERC_D_Ln9.ne3pg3_ne3pg3_mt232.FHISTC_LTso.izumi_nag.cam-cosp_rad_diags
+  NLFAIL SMS_D_Ld2.f45_f45_mg37.PC5.izumi_nag.cam-outfrq24h_port
+  NLFAIL SMS_D_Ln9.f10_f10_mt232.F1850.izumi_nag.cam-outfrq9s
+  NLFAIL SMS_D_Ln9.ne3pg3_ne3pg3_mt232.QPC7.izumi_nag.cam-carma_test_tracers
+  NLFAIL TMC_D_Ln9.f10_f10_mt232.FHIST_C5.izumi_nag.cam-mc_ttrac
+   - new SAD species types lists
+
+izumi/gnu/aux_cam:
+  DIFF SMS_D_Ln3.f10_f10_mg37.QPMOZ.izumi_gnu.cam-outfrq3s_chemproc
+   - expected baseline failure due to BAM SAD refactor
+
+  NLFAIL ERC_D_Ln9.C48_C48_mg17.QPC6.izumi_gnu.cam-outfrq9s
+  NLFAIL ERC_D_Ln9.f19_f19_mt232.FHIST.izumi_gnu.cam-lonlat_fv_diags
+  NLFAIL ERC_D_Ln9.mpasa480_mpasa480_mt232.FHISTC_LTso.izumi_gnu.cam-outfrq9s_mpasa480
+  NLFAIL ERC_D_Ln9.ne3pg3_ne3pg3_mt232.FGRAYRAD.izumi_gnu.cam-outfrq9s
+  NLFAIL ERC_D_Ln9.ne3pg3_ne3pg3_mt232.FHIST_C5.izumi_gnu.cam-carma_cosp_rad_diag_mam
+  NLFAIL ERC_D_Ln9.ne3pg3_ne3pg3_mt232.FHISTC_LTso.izumi_gnu.cam-sat_lcltod
+  NLFAIL ERC_D_Ln9.ne3pg3_ne3pg3_mt232.FTJ16.izumi_gnu.cam-outfrq9s
+  NLFAIL ERC_D_Ln9.ne3pg3_ne3pg3_mt232.QPC5.izumi_gnu.cam-outfrq9s
+  NLFAIL ERS_Ln9_P24x1.mpasa480_mpasa480.F2000climo.izumi_gnu.cam-outfrq9s_mpasa480
+  NLFAIL PLB_D_Ln9.f10_f10_mt232.FHIST_C5.izumi_gnu.cam-ttrac_loadbal0
+  NLFAIL PLB_D_Ln9.f10_f10_mt232.FHIST_C5.izumi_gnu.cam-ttrac_loadbal1
+  NLFAIL PLB_D_Ln9.f10_f10_mt232.FHIST_C5.izumi_gnu.cam-ttrac_loadbal3
+  NLFAIL SCT_D_Ln7.ne3_ne3_mg37.QPC6.izumi_gnu.cam-scm_prep_c6
+  NLFAIL SMS_D_Ln3.ne3pg3_ne3pg3_mt232.PC7.izumi_gnu.cam-pc7_ne3pg3
+  NLFAIL SMS_D_Ln9.f10_f10_mg37.FWmaHIST.izumi_gnu.cam-outfrq9s_mee_fluxes
+  NLFAIL SUB_D_Ln9.ne3pg3_ne3pg3_mt232.FHIST.izumi_gnu.cam-outfrq9s
+   - new SAD species types lists
+
+Summarize any changes to answers:
+  larger than roundoff for prognostic BAM, otherwise bit-for-bit
+
+===============================================================
+===============================================================
+
 Tag name: cam6_4_194
 Originator(s): jimmielin
 Date: Aug 7, 2026

src/chemistry/aerosol/aerosol_spec_utils.F90

@@ -0,0 +1,25 @@
+! Utility module for aerosol species types
+module aerosol_spec_utils
+
+  implicit none
+  private
+  public :: spec_type_in_list
+
+contains
+
+  ! returns TRUE if species type is found in type_list
+  logical function spec_type_in_list(spec_type, type_list)
+    character(len=*), intent(in) :: spec_type
+    character(len=*), intent(in) :: type_list(:)
+    integer :: i
+    spec_type_in_list = .false.
+    do i = 1, size(type_list)
+       if (len_trim(type_list(i)) == 0) cycle
+       if (trim(spec_type) == trim(type_list(i))) then
+          spec_type_in_list = .true.
+          return
+       end if
+    end do
+  end function spec_type_in_list
+
+end module aerosol_spec_utils

src/chemistry/aerosol/aerosol_state_mod.F90

@@ -65,6 +65,7 @@ module aerosol_state_mod
      procedure :: convcld_actfrac
      procedure :: sol_factb_interstitial
      procedure(aero_aqu_gain_binfraction), deferred :: aqu_gain_binfraction
+     procedure(aero_surf_area_dens), deferred :: surf_area_dens
 
   end type aerosol_state
 
@@ -299,6 +300,32 @@ subroutine aero_aqu_gain_binfraction(self, aero_props, type, qcw, delso4_o3rxn,
 
      end subroutine aero_aqu_gain_binfraction
 
+     !------------------------------------------------------------------------
+     ! aerosol surface area density
+     !------------------------------------------------------------------------
+     subroutine aero_surf_area_dens(self, aero_props, types_list, ncol, nlev, beglev, endlev, &
+                                    relhum, pmid, temp, pi, sad, reff, sfc, dm_aer)
+       import :: aerosol_state, aerosol_properties, r8
+
+       class(aerosol_state), intent(in) :: self
+       class(aerosol_properties), intent(in) :: aero_props ! aerosol properties object
+       character(len=*), intent(in) :: types_list(:) ! list of aerosol types to include
+       integer,  intent(in)  :: ncol        ! number of columns
+       integer,  intent(in)  :: nlev        ! number of levels
+       integer,  intent(in)  :: beglev(:)   ! beginning model level index
+       integer,  intent(in)  :: endlev(:)   ! ending model level index
+       real(r8), intent(in)  :: relhum(:,:) ! relative humidity
+       real(r8), intent(in)  :: pmid(:,:)   ! mid-level pressure (Pa)
+       real(r8), intent(in)  :: temp(:,:)   ! temperature (K)
+       real(r8), intent(in)  :: pi          ! pi mathematical constant
+
+       real(r8), intent(out) :: sad(:,:)    ! surface area density (cm2/cm3)
+       real(r8), intent(out) :: reff(:,:)   ! effective radius (units cm)
+       real(r8), optional, intent(out) :: sfc(:,:,:) ! surface area density per bin (cm2/cm3)
+       real(r8), optional, intent(out) :: dm_aer(:,:,:) ! diameter per bin (cm)
+
+     end subroutine aero_surf_area_dens
+
   end interface
 
 contains
@@ -967,5 +994,4 @@ function sol_factb_interstitial(self, bin_ndx, ncol, nlev, aero_props) result(so
 
   end function sol_factb_interstitial
 
-
 end module aerosol_state_mod