cam6_4_167: 1850 MTt4s namelist defaults

bld/namelist_files/namelist_defaults_cam.xml

@@ -714,7 +714,8 @@
 <!-- Time-variant chemistry surface values -->
 <bndtvghg>atm/cam/ggas/ghg_hist_1765-2005_c091218.nc</bndtvghg>
 <flbc_file>atm/waccm/lb/LBC_1765-2100_1.9x2.5_CCMI_RCP60_za_RNOCStrend_c141002.nc</flbc_file>
-<flbc_file chem="ghg_mam4">atm/waccm/lb/LBC_17500116-20150116_CMIP6_0p5degLat_c180905.nc</flbc_file>
+<flbc_file chem="ghg_mam4" phys="cam6">atm/waccm/lb/LBC_17500116-20150116_CMIP6_0p5degLat_c180905.nc</flbc_file>
+<flbc_file                 phys="cam7">atm/waccm/lb/CMIP7/LBC_17500116-20221216_CMIP7_0p5degLat_OCSupdate_c250523.nc</flbc_file>
 
 <!-- Time-variant CO2 fossil fuel emissions -->
 <co2flux_fuel_file hgrid="0.9x1.25" sim_year="1850-2015">atm/cam/ggas/emissions-cmip6_CO2_anthro_surface_175001-201512_fv_0.9x1.25_c20181011.nc</co2flux_fuel_file>
@@ -866,6 +867,7 @@
 <gw_prndl     chem="trop_strat_mam4_slh">0.5d0  </gw_prndl>
 <gw_prndl     chem="trop_strat_mam5_slh">0.5d0  </gw_prndl>
 <gw_oro_south_fac                       >1.d0   </gw_oro_south_fac>
+<gw_oro_south_fac         model_top="mt">1.d0   </gw_oro_south_fac>
 <gw_oro_south_fac         waccm_phys="1">2.d0   </gw_oro_south_fac>
 <gw_oro_south_fac         model_top="ht">2.d0   </gw_oro_south_fac>
 <gw_oro_south_fac chem="geoschem_mam4">2.d0   </gw_oro_south_fac>
@@ -878,6 +880,7 @@
 <gw_oro_south_fac carma="trop_strat_soa1">2.D0</gw_oro_south_fac>
 <gw_oro_south_fac carma="trop_strat_soa5">2.D0</gw_oro_south_fac>
 <gw_lndscl_sgh                          >.true. </gw_lndscl_sgh>
+<gw_lndscl_sgh            model_top="mt">.true. </gw_lndscl_sgh>
 <gw_lndscl_sgh            waccm_phys="1">.false.</gw_lndscl_sgh>
 <gw_lndscl_sgh            model_top="ht">.false.</gw_lndscl_sgh>
 <gw_lndscl_sgh chem="geoschem_mam4">.false.</gw_lndscl_sgh>
@@ -2608,7 +2611,7 @@
 <seasalt_emis_scale ver="mam7"                                           >1.62D0</seasalt_emis_scale>
 <seasalt_emis_scale ver="strat"                                          >0.90D0</seasalt_emis_scale>
 <seasalt_emis_scale ver="strat" clubb_sgs="1"                            >1.00D0</seasalt_emis_scale>
-<seasalt_emis_scale ver="strat" clubb_sgs="1" phys="cam7"                >1.50D0</seasalt_emis_scale>
+<seasalt_emis_scale ver="strat" clubb_sgs="1" phys="cam7"                >1.55D0</seasalt_emis_scale>
 <seasalt_emis_scale ver="strat" clubb_sgs="1" hgrid="1.9x2.5" phys="cam6">1.10D0</seasalt_emis_scale>
 <seasalt_emis_scale ver="strat" clubb_sgs="1" silhs="1"                  >0.60D0</seasalt_emis_scale>
 

bld/namelist_files/use_cases/1850_cam_lt.xml

@@ -7,7 +7,6 @@
 <solar_data_type>    FIXED            </solar_data_type>
 
 <!-- LBC Files : -->
-<flbc_file>atm/waccm/lb/CMIP7/LBC_17500116-20221216_CMIP7_0p5degLat_c250326.nc</flbc_file>
 <flbc_cycle_yr>1850</flbc_cycle_yr>
 <flbc_type>'CYCLICAL'</flbc_type>
 <flbc_list>'CO2','CH4','N2O','CFC11','CFC12','CFC11eq'</flbc_list>

bld/namelist_files/use_cases/1850_cam_mt.xml

@@ -7,7 +7,6 @@
 <solar_data_type>    FIXED            </solar_data_type>
 
 <!-- LBC Files : -->
-<flbc_file>atm/waccm/lb/CMIP7/LBC_17500116-20221216_CMIP7_0p5degLat_c250326.nc</flbc_file>
 <flbc_cycle_yr>1850</flbc_cycle_yr>
 <flbc_type>'CYCLICAL'</flbc_type>
 <flbc_list>'CO2','CH4','N2O','CFC11','CFC12','CFC11eq'</flbc_list>

bld/namelist_files/use_cases/hist_cam_lt.xml

@@ -7,7 +7,6 @@
 <solar_irrad_data_file>atm/cam/solar/SolarForcingCMIP7-4.6_18491230-20240101_sumEPP_c20250630.nc</solar_irrad_data_file>
 
 <!-- LBC Files -->
-<flbc_file>atm/waccm/lb/CMIP7/LBC_17500116-20221216_CMIP7_0p5degLat_c250326.nc</flbc_file>
 <flbc_type>'SERIAL'</flbc_type>
 <flbc_list>'CO2','CH4','N2O','CFC11','CFC12','CFC11eq'</flbc_list>
 

bld/namelist_files/use_cases/hist_cam_mt.xml

@@ -7,7 +7,6 @@
 <solar_irrad_data_file>atm/cam/solar/SolarForcingCMIP7-4.6_18491230-20240101_sumEPP_c20250630.nc</solar_irrad_data_file>
 
 <!-- LBC Files -->
-<flbc_file>atm/waccm/lb/CMIP7/LBC_17500116-20221216_CMIP7_0p5degLat_c250326.nc</flbc_file>
 <flbc_type>'SERIAL'</flbc_type>
 <flbc_list>'CO2','CH4','N2O','CFC11','CFC12','CFC11eq'</flbc_list>
 

bld/namelist_files/use_cases/hist_trop_strat_t4s_cam7.xml

@@ -15,10 +15,9 @@
 
 <!-- Lower boundary concentrations -->
 <flbc_type>SERIAL</flbc_type>
-<flbc_file>atm/waccm/lb/LBC_17500116-25001216_CMIP6_SSP585_0p5degLat_c20200824.nc</flbc_file>
 <flbc_list>
-  'CCL4', 'CF2CLBR', 'CF3BR', 'CFC11', 'CFC113', 'CFC12', 'CH3BR', 'CH3CCL3', 'CH3CL', 'CH4', 'CO2', 'H2',
-  'HCFC22', 'N2O', 'CFC114', 'CFC115', 'HCFC141B', 'HCFC142B', 'H2402', 'OCS', 'SF6', 'CFC11eq'
+ 'CCL4', 'CF2CLBR', 'CF3BR', 'CFC11', 'CFC113', 'CFC12', 'CH3BR', 'CH3CCL3', 'CH3CL', 'CH4', 'CO2', 'H2',
+ 'HCFC22', 'N2O', 'CFC114', 'CFC115', 'HCFC141B', 'HCFC142B', 'CH2BR2', 'CHBR3', 'H2402', 'OCS', 'SF6', 'CFC11eq'
 </flbc_list>
 
 <!-- history output -->

bld/namelist_files/use_cases/waccm_ma_hist_cam7.xml

@@ -22,10 +22,9 @@
 
 <!-- LBC, UBC Files -->
 <flbc_type>SERIAL</flbc_type>
-<flbc_file>atm/waccm/lb/CMIP7/LBC_17500116-20221216_CMIP7_0p5degLat_c250326.nc</flbc_file>
 <flbc_list>
  'CCL4', 'CF2CLBR', 'CF3BR', 'CFC11', 'CFC113', 'CFC12', 'CH3BR', 'CH3CCL3', 'CH3CL', 'CH4', 'CO2', 'H2',
- 'HCFC22', 'N2O', 'CFC114', 'CFC115', 'HCFC141B', 'HCFC142B', 'CH2BR2', 'CHBR3', 'H2402', 'OCS', 'CFC11eq'
+ 'HCFC22', 'N2O', 'CFC114', 'CFC115', 'HCFC141B', 'HCFC142B', 'CH2BR2', 'CHBR3', 'H2402', 'OCS', 'SF6', 'CFC11eq'
 </flbc_list>
 
 <!-- Upper Boundary -->

bld/namelist_files/use_cases/waccm_sc_hist_cam7.xml

@@ -18,7 +18,6 @@
 
 <!-- LBC, UBC Files -->
 <flbc_type>SERIAL</flbc_type>
-<flbc_file>atm/waccm/lb/CMIP7/LBC_17500116-20221216_CMIP7_0p5degLat_c250326.nc</flbc_file>
 <flbc_list>'CO2','CH4','N2O','CFC11','CFC12','CFC11eq'</flbc_list>
 
 <!-- upper atmos forcings -->

cime_config/testdefs/testlist_cam.xml

@@ -2022,6 +2022,16 @@
       <option name="comment" >Medium-top CAM-Chem with simpler climate chemistry</option>
     </options>
   </test>
+  <test compset="1850C_CAM70%MT%CT4S2_CLM60%SP_CICE%PRES_DOCN%DOM_MOSART_SGLC_SWAV_SESP" grid="ne30pg3_ne30pg3_mt232" name="SMS_D_Ln9" testmods="cam/outfrq9s">
+    <machines>
+      <machine name="derecho" compiler="intel" category="camchem"/>
+      <machine name="derecho" compiler="intel" category="aux_cam"/>
+    </machines>
+    <options>
+      <option name="wallclock">00:40:00</option>
+      <option name="comment" >1850 Medium-top CAM-Chem with simpler climate chemistry</option>
+    </options>
+  </test>
   <test compset="FW2000climo" grid="f09_f09_mg17" name="SMS_Ld1" testmods="cam/outfrq1d">
     <machines>
       <machine name="derecho" compiler="intel" category="aux_cam"/>

doc/ChangeLog

@@ -1,5 +1,163 @@
 ===============================================================
 
+Tag name: cam6_4_167
+Originator(s): fvitt
+Date: 23 Apr 2026
+One-line Summary: Updates for cam7 compsets
+Github PR URL: https://github.com/ESCOMP/CAM/pull/1534
+
+Purpose of changes (include the issue number and title text for each relevant GitHub issue):
+
+ Update LBC file for cam7 compsets #1539
+ Update default namelist settings for 1850 MTt4s and adjust default history fields #1527
+ Improve error messaging in O2 chemistry #1528
+
+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, tilmes, cecilehannay
+
+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/namelist_defaults_cam.xml
+ - update cam7 default namelist settings
+
+M       bld/namelist_files/use_cases/1850_cam_lt.xml
+M       bld/namelist_files/use_cases/1850_cam_mt.xml
+M       bld/namelist_files/use_cases/hist_cam_lt.xml
+M       bld/namelist_files/use_cases/hist_cam_mt.xml
+M       bld/namelist_files/use_cases/waccm_sc_hist_cam7.xml
+ - default LBC file is now specified in namelist_defaults_cam.xml
+
+M       bld/namelist_files/use_cases/1850_trop_strat_t4s_cam7.xml
+ - namelist updates for 1850 MTt4s
+
+M       bld/namelist_files/use_cases/waccm_ma_hist_cam7.xml
+M       bld/namelist_files/use_cases/hist_trop_strat_t4s_cam7.xml
+ - update flbc_list
+
+M       cime_config/testdefs/testlist_cam.xml
+ - add test for 1850 MTt4s
+
+M       src/chemistry/mozart/mo_jshort.F90
+ - improve error checking and reporting
+
+M       src/physics/cam/aerosol_optics_cam.F90
+ - modify history_aero_optics default fields
+
+M       src/physics/cam/ndrop.F90
+ - include CCN4 in history_amwg default fields
+
+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:
+
+  DIFF ERC_D_Ln9.mpasa120_mpasa120.FHISTC_LTso.derecho_intel.cam-outfrq9s_mpasa120
+  DIFF ERP_D_Ln9.ne30pg3_ne30pg3_mt232.F1850C_MTso.derecho_intel.cam-outfrq9s
+  DIFF ERP_Ld3.ne16pg3_ne16pg3_mg17.FHISTC_WAt1ma.derecho_intel.cam-reduced_hist1d
+  DIFF ERP_Ld3.ne30pg3_ne30pg3_mt232.FHISTC_MTt4s.derecho_intel.cam-outfrq1d_aoa
+  DIFF ERR_Ln9.ne16pg3_ne16pg3_mt232.FHISTC_LTso.derecho_intel.cam-outfrq9s_bwic
+  DIFF ERS_Ln9.ne30pg3_ne30pg3_mg17.FHISTC_WXma.derecho_intel.cam-outfrq9s_ctem
+  DIFF SMS_C2_D_Ln9.ne16pg3_ne16pg3_mg17.FHISTC_WXma.derecho_intel.cam-outfrq9s
+  DIFF SMS_D_Ln9.ne30pg3_ne30pg3_mt232.FHISTC_MTso.derecho_intel.cam-outfrq9s
+  DIFF SMS_D_Ln9_P1280x1.ne30pg3_ne30pg3_mt232.FHISTC_MTt1s.derecho_intel.cam-outfrq9s_Leung_dust
+  DIFF ERP_Ln9.ne30pg3_ne30pg3_mg17.FHISTC_WAma.derecho_intel.cam-outfrq9s
+   - expected differences due to updates in LBC file and seasalt_emis_scale factor
+
+  DIFF SMS_D_Ln9.ne30pg3_ne30pg3_mt232.1850C_CAM70%MT%CT4S2_CLM60%SP_CICE%PRES_DOCN%DOM_MOSART_SGLC_SWAV_SESP.derecho_intel.cam-outfrq9s
+   - new test -- no baselines to compare against
+
+  DIFF ERC_D_Ln9.f09_f09_mt232.FHIST_BDRD.derecho_intel.cam-outfrq9s
+  DIFF ERC_D_Ln9.f19_f19_mt232.QPC6.derecho_intel.cam-outfrq3s_cosp
+  DIFF ERC_D_Ln9.mpasa120_mpasa120.F2000climo.derecho_intel.cam-outfrq9s_mpasa120
+  DIFF ERC_Ln9.C96_C96_mt232.F2000climo.derecho_intel.cam-outfrq9s
+  DIFF ERI_D_Ln18.f09_f09_mt232.FHIST.derecho_intel.cam-outfrq3s_eri
+  DIFF ERI_D_Ln18.f19_f19_mt232.FHIST_C5.derecho_intel.cam-outfrq3s_eri
+  DIFF ERP_D_Ln9_P64x2.f09_f09_mg17.QSC6.derecho_intel.cam-outfrq9s
+  DIFF ERP_Ln9.f09_f09_mg17.FCSD_HCO.derecho_intel.cam-outfrq9s
+  DIFF ERP_Ln9.f19_f19_mg17.FWsc1850.derecho_intel.cam-outfrq9s
+  DIFF ERP_Ln9.ne30pg3_ne30pg3_mg17.FCnudged.derecho_intel.cam-outfrq9s
+  DIFF ERS_Ln9.f09_f09_mg17.FX2000.derecho_intel.cam-outfrq9s
+  DIFF ERS_Ln9.f19_f19_mg17.FXSD.derecho_intel.cam-outfrq9s
+  DIFF SMS_D_Ln9.f09_f09_mg17.FCts2nudged.derecho_intel.cam-outfrq9s_leapday
+  DIFF SMS_D_Ln9.f09_f09_mg17.FCvbsxHIST.derecho_intel.cam-outfrq9s
+  DIFF SMS_D_Ln9.f09_f09_mg17.FSD.derecho_intel.cam-outfrq9s
+  DIFF SMS_D_Ln9.f19_f19_mg17.FCARMA2000climo.derecho_intel.cam-outfrq9s
+  DIFF SMS_D_Ln9.f19_f19_mg17.FCHIST_SLH.derecho_intel.cam-outfrq9s
+  DIFF SMS_D_Ln9.f19_f19_mg17.FWma2000climo.derecho_intel.cam-outfrq9s
+  DIFF SMS_D_Ln9.f19_f19_mg17.FWma2000climo.derecho_intel.cam-outfrq9s_waccm_ma_mam4
+  DIFF SMS_D_Ln9.f19_f19_mg17.QPC2000climo.derecho_intel.cam-outfrq3s_usecase
+  DIFF SMS_D_Ln9.f19_f19_mt232.FHIST_C5.derecho_intel.cam-mam7
+  DIFF SMS_D_Ln9.ne0ARCTICne30x4_ne0ARCTICne30x4_mt12.FHIST.derecho_intel.cam-outfrq9s
+  DIFF SMS_Ld1.f09_f09_mg17.FCHIST_GC.derecho_intel.cam-outfrq1d
+  DIFF SMS_Ld1.f09_f09_mg17.FW2000climo.derecho_intel.cam-outfrq1d
+  DIFF SMS_Ld1.ne30pg3_ne30pg3_mg17.FC2010climo.derecho_intel.cam-outfrq1d
+  DIFF SMS_Lh12.f09_f09_mg17.FCSD_HCO.derecho_intel.cam-outfrq3h
+  DIFF SMS_Ln9.ne30pg3_ne30pg3_mg17.FW2000climo.derecho_intel.cam-outfrq9s_rrtmgp
+  DIFF SMS_D_Ln9_P1536x1.ne0CONUSne30x8_ne0CONUSne30x8_mt12.FCHIST.derecho_intel.cam-outfrq9s
+  - differ only in field list, otherwise bit-for-bit
+
+derecho/nvhpc/aux_cam:
+    FAIL ERS_Ln9.ne30pg3_ne30pg3_mt232.FHISTC_LTso.derecho_nvhpc.cam-outfrq9s_gpu_default COMPARE_base_rest
+    - pre-existing restart test failure
+
+    FAIL ERS_Ln9.ne30pg3_ne30pg3_mt232.FHISTC_LTso.derecho_nvhpc.cam-outfrq9s_gpu_default NLCOMP
+    FAIL ERS_Ln9.ne30pg3_ne30pg3_mt232.FHISTC_LTso.derecho_nvhpc.cam-outfrq9s_gpu_default BASELINE /glade/campaign/cesm/community/amwg/cam_baselines/cam6_4_166_nvhpc: DIFF
+   - expected differences due to updates in LBC file and seasalt_emis_scale factor
+
+izumi/nag/aux_cam:
+  FAIL ERC_D_Ln9.f10_f10_mt232.FHIST_C5.izumi_nag.cam-outfrq3s_subcol
+   - pre-existing failure -- see https://github.com/ESCOMP/CAM/issues/1514
+
+  DIFF ERC_D_Ln9.ne3pg3_ne3pg3_mt232.FHISTC_LTso.izumi_nag.cam-outfrq9s_nochem
+  DIFF ERC_D_Ln9.ne3pg3_ne3pg3_mt232.FHISTC_LTso.izumi_nag.cam-cosp_rad_diags
+   - expected differences due to updates in LBC file and seasalt_emis_scale factor
+
+  DIFF ERC_D_Ln9.f10_f10_mg37.QPWmaC6.izumi_nag.cam-outfrq3s
+  DIFF ERC_D_Ln9.f10_f10_mt232.FHIST.izumi_nag.cam-outfrq3s_cospsathist
+  DIFF SMS_D_Ln9.f10_f10_mt232.F1850.izumi_nag.cam-outfrq9s
+  DIFF TMC_D_Ln9.f10_f10_mt232.FHIST_C5.izumi_nag.cam-mc_ttrac
+   - differ only in field list, otherwise bit-for-bit
+
+izumi/gnu/aux_cam:
+  DIFF ERC_D_Ln9.C48_C48_mg17.QPC6.izumi_gnu.cam-outfrq9s
+  DIFF ERC_D_Ln9.f10_f10_mg37.QPC4.izumi_gnu.cam-outfrq3s_diags
+  DIFF ERC_D_Ln9.f19_f19_mt232.FHIST.izumi_gnu.cam-lonlat_fv_diags
+  DIFF ERC_D_Ln9.ne3pg3_ne3pg3_mt232.FHIST_C5.izumi_gnu.cam-carma_cosp_rad_diag_mam
+  DIFF ERC_D_Ln9.ne3pg3_ne3pg3_mt232.QPC5.izumi_gnu.cam-outfrq9s
+  DIFF ERS_Ln9_P24x1.mpasa480_mpasa480.F2000climo.izumi_gnu.cam-outfrq9s_mpasa480
+  DIFF PLB_D_Ln9.f10_f10_mt232.FHIST_C5.izumi_gnu.cam-ttrac_loadbal0
+  DIFF PLB_D_Ln9.f10_f10_mt232.FHIST_C5.izumi_gnu.cam-ttrac_loadbal1
+  DIFF PLB_D_Ln9.f10_f10_mt232.FHIST_C5.izumi_gnu.cam-ttrac_loadbal3
+  DIFF SMS_D_Ln9.f10_f10_mg37.FWmaHIST.izumi_gnu.cam-outfrq9s_mee_fluxes
+  DIFF SUB_D_Ln9.ne3pg3_ne3pg3_mt232.FHIST.izumi_gnu.cam-outfrq9s
+   - differ only in field list, otherwise bit-for-bit
+
+  DIFF ERC_D_Ln9.mpasa480_mpasa480_mt232.FHISTC_LTso.izumi_gnu.cam-outfrq9s_mpasa480
+  DIFF ERC_D_Ln9.ne3pg3_ne3pg3_mt232.FHISTC_LTso.izumi_gnu.cam-sat_lcltod
+   - expected differences due to updates in LBC file and seasalt_emis_scale factor
+
+  NLFAIL SMS_D_Ln3.ne3pg3_ne3pg3_mt232.PC7.izumi_gnu.cam-pc7_ne3pg3
+   - new LBC file
+
+Summarize any changes to answers:
+ Large than round-off due to updates in LBC file and seasalt_emis_scale factor
+
+===============================================================
+===============================================================
+
 Tag name: cam6_4_166
 Originator(s): huebleruwm, adamrher, cacraigucar
 Date: April 21, 2026

src/chemistry/mozart/mo_jshort.F90

@@ -227,7 +227,7 @@ subroutine get_crs( xs_short_file, sht_indexer )
             else
                write(iulog,*) 'get_crs : ',rxt_tag_lst(m)(:len_trim(rxt_tag_lst(m))),' alias ', &
                     pht_alias_lst(m,1)(:len_trim(pht_alias_lst(m,1))),' not in dataset'
-               call endrun
+               call endrun('mo_jshort::get_crs error')
             end if
          end if
       end do
@@ -315,7 +315,7 @@ subroutine get_crs( xs_short_file, sht_indexer )
       deallocate( xs_species )
       if( ndx /= nj ) then
          write(iulog,*) 'get_crs : ndx count /= cross section count'
-         call endrun
+         call endrun('mo_jshort::get_crs: ndx count /= cross section count')
       end if
       !------------------------------------------------------------------------------
       !       ... get jo3 cross sections
@@ -385,6 +385,7 @@ subroutine xs_init(xs_coef_file)
       integer :: istat	! i/o status
       integer :: i, j
       character(len=256) :: locfn
+      character(len=256) :: errstr
 
 !----------------------------------------------------------------------
 !	... Get first strato photo rate file
@@ -403,8 +404,8 @@ subroutine xs_init(xs_coef_file)
 !----------------------------------------------------------------------
 !	... Open error exit
 !----------------------------------------------------------------------
-            write(iulog,*) 'xs_init: error ',istat,' opening file ',trim(locfn)
-            call endrun
+            write(errstr,*) 'mo_jshort::xs_init: error ',istat,' opening file ',trim(locfn)
+            call endrun(trim(errstr))
          end if
 !----------------------------------------------------------------------
 !	... read file
@@ -414,16 +415,16 @@ subroutine xs_init(xs_coef_file)
             read(unit,903,iostat=istat) ac(i,:)
             if( istat /= 0 ) then
                write(iulog,*) 'xs_init: error ',istat,' reading ac'
-               call endrun
+               call endrun('mo_jshort::xs_init read file error')
             end if
          end do
 
          read(unit,901)
          do i = 1,20
             read(unit,903,iostat=istat) bc(i,:)
             if( istat /= 0 ) then
-               write(iulog,*) 'xs_init: error ',istat,' reading bc'
-               call endrun
+               write(errstr,*) 'xs_init: error ',istat,' reading bc'
+               call endrun(trim(errstr))
             end if
          end do
          close( unit )
@@ -619,6 +620,9 @@ subroutine jshort_hrates( nlev, zen, o2_vmr, o3_vmr, o2cc, &
        real(r8) :: tsrb(nlev,nsrbtuv)       ! Transmission in the SRB
        real(r8) :: xs_o2srb(nlev,nsrbtuv)   ! Cross section * QY for O2 in SRB
 
+       ! check for realistic O2 concentrations
+       call check_o2_col( o2cc )
+
       allocate( fnorm(nlev,nw),stat=astat )
       if( astat /= 0 ) then
          call alloc_err( astat, 'jshort_hrates', 'fnorm', nw*nlev )
@@ -944,6 +948,9 @@ subroutine jshort_photo( nlev, zen, n2cc, o2cc, o3cc, &
         real(r8) :: tsrb(nlev,nsrbtuv)       ! Transmission in the SRB
 	real(r8) :: xs_o2srb(nlev,nsrbtuv)   ! Cross section * QY for O2 in SRB
 
+        ! check for realistic O2 concentrations
+        call check_o2_col( o2cc )
+
       allocate( fnorm(nlev,nw),stat=astat )
       if( astat /= 0 ) then
 	 call alloc_err( astat, 'jshort_photo', 'fnorm', nw*nlev )
@@ -1487,6 +1494,7 @@ subroutine calc_o2srb( nlev, nid, o2col, tlev, tsrb, xscho2 )
       real(r8)    :: dtsrb(nlev)
       real(r8)    :: tsrb_rev(nlev,nsrbtuv)
       real(r8)    :: xs(nsrbtuv)
+      character(len=256) :: errstr
 
 !------------------------------------------------------------------------------
 !     ... Calculate cross sections
@@ -1562,8 +1570,8 @@ subroutine calc_o2srb( nlev, nid, o2col, tlev, tsrb, xscho2 )
                term1 = log( xscho2(k+1,i)/xscho2(k,i) )
                term2 = log( o2col(k+1)/o2col(k) )
 	       if( term2 == 0._r8 ) then
-                  write(iulog,*) 'calc_o2srb : o2col(k:k+1),xscho2(k:k+1,i) = ',o2col(k:k+1),xscho2(k:k+1,i),' @ i,k = ',i,k
-	          call endrun
+                  write(errstr,*) 'calc_o2srb : o2col(k:k+1),xscho2(k:k+1,i) = ',o2col(k:k+1),xscho2(k:k+1,i),' @ i,k = ',i,k
+	          call endrun(trim(errstr))
 	       end if
                den = 1._r8 + log( xscho2(k+1,i)/xscho2(k,i) )/log( o2col(k+1)/o2col(k) )
                dto2 = abs(num/den)
@@ -1870,4 +1878,15 @@ end function pjno
 
       end subroutine calc_jno
 
+      !----------------------------------------------------------------
+      subroutine check_o2_col( o2cc )
+        real(r8), intent(in) :: o2cc(:) ! o2 conc (mol/cm^3)
+
+        if (maxval(o2cc)<1.0_r8) then
+           write(*,*) 'mo_jshort input O2 (mol/cm^3): ',o2cc
+           call endrun('mo_jshort -- unrealistic O2 concentrations needed for absorption')
+        end if
+
+      end subroutine check_o2_col
+
       end module mo_jshort