start ChangeLog

Author: fvitt

doc/ChangeLog

@@ -1,5 +1,100 @@
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+Tag name: cam6_4_156
+Originator(s): fvitt, tilmes
+Date: 6 Mar 2026
+One-line Summary: Fix issue with prescribed volcanic aerosols
+Github PR URL: https://github.com/ESCOMP/CAM/pull/1495
+
+Purpose of changes (include the issue number and title text for each relevant GitHub issue):
+
+ Fix issue with 5th mode of the prescribed volcanic sulfate.
+ Issue #1494
+
+ Update IC file for B1850C_MTt4s compset.
+ Issue #1493
+
+Describe any changes made to build system: N/A
+
+Describe any changes made to the namelist: N/A
+
+List any changes to the defaults for the boundary datasets: N/A
+
+Describe any substantial timing or memory changes: N/A
+
+Code reviewed by: cacraigucar
+
+List all files eliminated: N/A
+
+List all files added and what they do: N/A
+
+List all existing files that have been modified, and describe the changes:
+
+M       bld/namelist_files/use_cases/1850_cam_mt.xml
+ - update prescribed ozone and strataero inputs
+ - set rad_climate to include VOLC_MMR5 (prescrided 5th mode of volcanic sulfate)
+   and use corrected physprop file for VOLC_MMR5
+
+M       bld/namelist_files/use_cases/1850_trop_strat_t4s_cam7.xml
+ - update IC file (to include O2)
+
+M       cime_config/testdefs/testmods_dirs/cam/outfrq9s_cam7_presc_volc/user_nl_cam
+ - set rad_climate to include VOLC_MMR5 (prescrided 5th mode of volcanic sulfate)
+ - use corrected physprop file for VOLC_MMR5
+
+M       src/chemistry/modal_aero/aero_model.F90
+ - output diameters of all 5 modes when history_cesm_forcing is TRUE
+
+M       src/chemistry/mozart/mo_chm_diags.F90
+ - output so4 of the 5th mode when history_cesm_forcing is TRUE
+
+M       src/physics/cam/aerosol_optics_cam.F90
+ - use correct radius (5th mode) for VOLC_MMR5
+ - call output_bin_diags for BAM aerosols (more diagnistcis)
+
+M       src/physics/cam/phys_prop.F90
+ - add volcanic_radius5 to the list of valid optics methods
+
+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:
+
+derecho/nvhpc/aux_cam:
+
+izumi/nag/aux_cam:
+
+izumi/gnu/aux_cam:
+
+CAM tag used for the baseline comparison tests if different than previous
+tag:
+
+Summarize any changes to answers, i.e.,
+- what code configurations:
+- what platforms/compilers:
+- nature of change (roundoff; larger than roundoff but same climate; new
+  climate):
+
+If bitwise differences were observed, how did you show they were no worse
+than roundoff?
+
+If this tag changes climate describe the run(s) done to evaluate the new
+climate in enough detail that it(they) could be reproduced, i.e.,
+- source tag (all code used must be in the repository):
+- platform/compilers:
+- configure commandline:
+- build-namelist command (or complete namelist):
+- MSS location of output:
+
+MSS location of control simulations used to validate new climate:
+
+URL for AMWG diagnostics output used to validate new climate:
+
+===============================================================
+===============================================================
+
 Tag name: cam6_4_155
 Originator(s): cacraig, jimmielin
 Date: Feb 24, 2026