Merge pull request #929 from brian-eaton/nstep0

cam6_3_141: Improve handling of 0th / initial time in history output

bld/namelist_files/namelist_definition.xml

@@ -1882,6 +1882,15 @@ the {{ hilight }}fincl#{{ closehilight }} namelist items.
 Default: FALSE
 </entry>
 
+<entry id="write_nstep0" type="logical"  category="history"
+       group="cam_history_nl" valid_values="" >
+If true then write the nstep==0 time sample to all history files except
+the monthly average file.  This output is primarily useful for development
+and debugging as it captures changes to the model state made during the
+initialization phase of the run.
+Default: FALSE
+</entry>
+
 <entry id="fexcl1" type="char*24(1000)"  category="history"
        group="cam_history_nl" valid_values="" >
 List of fields to exclude from the 1st history file (by default the name

cime_config/testdefs/testmods_dirs/cam/cam4_port/user_nl_cam

@@ -13,3 +13,4 @@
  rad_data_output = .false.
  mfilt=100,100
  nhtfrq=-120,73
+ write_nstep0 = .true.

cime_config/testdefs/testmods_dirs/cam/cam4_port5d/user_nl_cam

@@ -13,6 +13,7 @@
  rad_data_output = .false.
  mfilt=100,100
  nhtfrq=-120,73
+ write_nstep0 = .true.
  ncdata='$DIN_LOC_ROOT/atm/cam/inic/fv/aqua_0006-01-01_1.9x2.5_L26_c161020.nc'
  use_topo_file=.false. 
  atm_dep_flux=.false.

cime_config/testdefs/testmods_dirs/cam/cam5_port_f45/user_nl_cam

@@ -13,3 +13,4 @@
  rad_data_output = .false.
  mfilt=100,100
  nhtfrq=-120,73
+ write_nstep0 = .true.

cime_config/testdefs/testmods_dirs/cam/cam5_port_ne30/user_nl_cam

@@ -13,3 +13,4 @@
  rad_data_output = .false.
  mfilt=100,100
  nhtfrq=-120,73
+ write_nstep0 = .true.

cime_config/testdefs/testmods_dirs/cam/cam6_port_f09/user_nl_cam

@@ -13,6 +13,7 @@
  rad_data_output = .false.
  mfilt=100,100
  nhtfrq=-120,73
+ write_nstep0 = .true.
 
  prescribed_strataero_3modes = .true.
  prescribed_strataero_cycle_yr          = 1999         

cime_config/testdefs/testmods_dirs/cam/nudging/user_nl_cam

@@ -7,6 +7,7 @@
  fincl3='U','V','T','Q','PS','Nudge_U','Nudge_V','Nudge_T','Nudge_Q','Target_U','Target_V','Target_T','Target_Q'
  nhtfrq=0,-6,1
  mfilt =1,4,48
+ write_nstep0 = .true.
 
  ncdata='$DIN_LOC_ROOT/atm/cam/nudging/ERAI_fv09_BILIN/ERAI_fv09_DART2.cam2.i.2009-01-01-00000.nc'
 /

cime_config/testdefs/testmods_dirs/cam/outfrq1d/user_nl_cam

@@ -1,3 +1,4 @@
 mfilt=1,1,1,1,1,1
 ndens=1,1,1,1,1,1
 nhtfrq=-24,-24,-24,-24,-24,-24
+write_nstep0 = .true.

cime_config/testdefs/testmods_dirs/cam/outfrq3h/user_nl_cam

@@ -1,3 +1,4 @@
 mfilt=1,1,1,1,1,1,1,1,1,1
 ndens=1,1,1,1,1,1,1,1,1,1
 nhtfrq=-3,-3,-3,-3,-3,-3,-3,-3,-3,-3
+write_nstep0 = .true.

cime_config/testdefs/testmods_dirs/cam/outfrq3s/user_nl_cam

@@ -1,5 +1,6 @@
 mfilt=1,1,1,1,1,1
 ndens=1,1,1,1,1,1
 nhtfrq=3,3,3,3,3,3
+write_nstep0=.true.
 inithist='ENDOFRUN'
 pbuf_global_allocate=.false.

cime_config/testdefs/testmods_dirs/cam/outfrq3s_cospsathist/user_nl_cam

@@ -1,6 +1,7 @@
  ndens=1,1,1,1,1,1
  nhtfrq=3,3,3,3,-2,3
  mfilt=1,1,1,1,1,1
+ write_nstep0=.true.
  sathist_track_infile='$DIN_LOC_ROOT/atm/cam/sat/satellite_profilelist_20020125_20101030_c110204_noleap.nc'
  sathist_fincl = 'Q','T','PS','U','V','FV'
  fincl3 = 'Q','T','PS','FV','UWzm:I'

cime_config/testdefs/testmods_dirs/cam/outfrq3s_diags/user_nl_cam

@@ -1,6 +1,7 @@
 mfilt=1,1,1,1,1,1
 ndens=2,2,2,2,2,2
 nhtfrq=3,3,3,3,3,3
+write_nstep0=.true.
 inithist='ENDOFRUN'
 history_amwg=.true.
 history_aerosol=.true.

cime_config/testdefs/testmods_dirs/cam/outfrq9s/user_nl_cam

@@ -1,4 +1,5 @@
 mfilt=1,1,1,1,1,1
 ndens=1,1,1,1,1,1
 nhtfrq=9,9,9,9,9,9
+write_nstep0=.true.
 inithist='ENDOFRUN'

cime_config/testdefs/testmods_dirs/cam/outfrq9s_apmee/user_nl_cam

@@ -1,6 +1,7 @@
 mfilt=1,1,1,1,1,1
 ndens=1,1,1,1,1,1
 nhtfrq=9,9,9,9,9,9
+write_nstep0=.true.
 inithist='ENDOFRUN'
 
 mee_ion_inline=.true.

cime_config/testdefs/testmods_dirs/cam/outfrq9s_mee_fluxes/user_nl_cam

@@ -1,6 +1,7 @@
 mfilt=1,1,1,1,1,1
 ndens=1,1,1,1,1,1
 nhtfrq=9,9,9,9,9,9
+write_nstep0=.true.
 inithist='ENDOFRUN'
 
 mee_fluxes_filepath='$DIN_LOC_ROOT/atm/waccm/mee/RBSP-ECT_FB_precip_c211124.nc'

cime_config/testdefs/testmods_dirs/cam/reduced_hist1d/user_nl_cam

@@ -2,6 +2,7 @@
  mfilt=1,1,1,1,1,1
  ndens=1,1,1,1,1,1
  nhtfrq=-24,-24,-24,-24,-24,-24
+ write_nstep0=.true.
 
  fincl1 = ' '
  fincl2 = ' '

cime_config/testdefs/testmods_dirs/cam/scm_prep/user_nl_cam

@@ -2,3 +2,4 @@ NDENS    = 1,1
 MFILT    = 1,10
 nhtfrq   = 0,1
 inithist_all = .true.
+write_nstep0 = .true.

cime_config/testdefs/testmods_dirs/cam/scm_prep_c6/user_nl_cam

@@ -2,3 +2,4 @@ NDENS    = 1,1
 MFILT    = 1,10
 nhtfrq   = 0,1
 inithist_all = .true.
+write_nstep0 = .true.

cime_config/testdefs/testmods_dirs/cam/scmarm/user_nl_cam

@@ -1,3 +1,4 @@
 mfilt=1500
 nhtfrq   = 1
 history_budget=.true.
+write_nstep0 = .true.

cime_config/testdefs/testmods_dirs/cam/silhs/user_nl_cam

@@ -1,5 +1,6 @@
 dtime = 1800
 nhtfrq = 0,-24,-6,-3
+write_nstep0 = .true.
 mfilt = 1,5000,5000
 ndens = 2,2,2,2,2,2
 history_budget = .true.

doc/ChangeLog

@@ -1,5 +1,168 @@
 ===============================================================
 
+Tag name: cam6_3_141
+Originator(s): eaton
+Date: 8 December 2023
+One-line Summary: Improve handling of 0th / initial time in history output
+Github PR URL: https://github.com/ESCOMP/CAM/pull/929
+
+Purpose of changes (include the issue number and title text for each relevant GitHub issue):
+
+. Issue #459 - Improve handling of 0th / initial time in history output
+  - Add namelist variable, write_nstep0, to control output of nstep==0 time
+    sample.  This output is now turned OFF by default.
+
+. resolves #459
+
+Describe any changes made to build system: none
+
+Describe any changes made to the namelist:
+. Add logical variable write_nstep0 to namelist group cam_history_nl.
+  Default value is .false.
+
+List any changes to the defaults for the boundary datasets: none
+
+Describe any substantial timing or memory changes: none
+
+Code reviewed by: cacraigucar, peverwhee
+
+List all files eliminated: none
+
+List all files added and what they do: none
+
+List all existing files that have been modified, and describe the changes:
+
+bld/namelist_files/namelist_definition.xml
+. Add logical variable write_nstep0 to namelist group cam_history_nl.
+  Default value is .false.
+
+doc/ChangeLog_template
+. remove cheyenne test results section
+
+cime_config/testdefs/testmods_dirs/cam/cam4_port/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/cam4_port5d/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/cam5_port_f45/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/cam5_port_ne30/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/cam6_port_f09/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/nudging/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/outfrq1d/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/outfrq3h/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/outfrq3s/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/outfrq3s_cospsathist/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/outfrq3s_diags/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/outfrq9s/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/outfrq9s_apmee/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/outfrq9s_mee_fluxes/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/reduced_hist1d/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/scm_prep/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/scm_prep_c6/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/scmarm/user_nl_cam
+cime_config/testdefs/testmods_dirs/cam/silhs/user_nl_cam
+. add write_nstep0=.true.
+  - This change to the namelist keeps the output files unchanged so
+    baselines pass.  It also keeps the nstep==0 output which is useful for
+    debugging.
+
+src/control/cam_history.F90
+. add write_nstep0 to namelist input and echo to atm.log file
+. wshist
+  - add logic for nstep==0 to the code section that determines when history
+    buffers are written to files.  If history buffers are not written at
+    nstep==0, then zero them.  This partial time step from the
+    initialization process shouldn't be accumulated with subsequent
+    timestep output.
+
+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:
+  ERP_Ln9_Vnuopc.C96_C96_mg17.F2000climo.derecho_intel.cam-outfrq9s_mg3 (Overall: PEND) details:
+  ERP_Ln9_Vnuopc.f09_f09_mg17.FCSD_HCO.derecho_intel.cam-outfrq9s (Overall: FAIL) details:
+- pre-existing failures
+
+  ERC_D_Ln9_Vnuopc.f19_f19_mg17.QPMOZ.derecho_intel.cam-outfrq3s (Overall: NLFAIL) details:
+  ERC_D_Ln9_Vnuopc.f19_f19_mg17.QPX2000.derecho_intel.cam-outfrq3s (Overall: NLFAIL) details:
+  ERP_D_Ln9.ne30pg3_ne30pg3_mg17.FLTHIST.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERP_D_Ln9_Vnuopc.f09_f09_mg17.QSC6.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERP_D_Ln9_Vnuopc.f19_f19_mg17.QPC6.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERP_D_Ln9_Vnuopc.ne30pg3_ne30pg3_mg17.F2000dev.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERP_Ld3_Vnuopc.f09_f09_mg17.FWHIST.derecho_intel.cam-reduced_hist1d (Overall: NLFAIL) details:
+  ERP_Lh12_Vnuopc.f19_f19_mg17.FW4madSD.derecho_intel.cam-outfrq3h (Overall: NLFAIL) details:
+  ERP_Ln9_P24x3_Vnuopc.f45_f45_mg37.QPWmaC6.derecho_intel.cam-outfrq9s_mee_fluxes (Overall: NLFAIL) details:
+  ERP_Ln9_Vnuopc.f09_f09_mg17.F1850.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERP_Ln9_Vnuopc.f09_f09_mg17.F2000climo.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERP_Ln9_Vnuopc.f09_f09_mg17.F2010climo.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERP_Ln9_Vnuopc.f09_f09_mg17.FHIST_BDRD.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERP_Ln9_Vnuopc.f19_f19_mg17.FWsc1850.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERP_Ln9_Vnuopc.ne30_ne30_mg17.FCnudged.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERP_Ln9_Vnuopc.ne30pg3_ne30pg3_mg17.FW2000climo.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERS_Ln9_Vnuopc.f09_f09_mg17.FX2000.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERS_Ln9_Vnuopc.f19_f19_mg17.FSPCAMS.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  ERS_Ln9_Vnuopc.f19_f19_mg17.FXSD.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SCT_D_Ln7_Vnuopc.T42_T42_mg17.QPC5.derecho_intel.cam-scm_prep (Overall: NLFAIL) details:
+  SMS_D_Ld5_Vnuopc.f19_f19_mg17.PC4.derecho_intel.cam-cam4_port5d (Overall: NLFAIL) details:
+  SMS_D_Ln9.ne30pg3_ne30pg3_mg17.FMTHIST.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_D_Ln9_Vnuopc.f09_f09_mg17.FCvbsxHIST.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_D_Ln9_Vnuopc.f09_f09_mg17.FSD.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_D_Ln9_Vnuopc.f19_f19_mg17.FWma2000climo.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_D_Ln9_Vnuopc.f19_f19_mg17.QPC5M7.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_D_Ln9_Vnuopc.ne16_ne16_mg17.FX2000.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_D_Ln9_Vnuopc.ne16_ne16_mg17.QPX2000.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_D_Ln9_Vnuopc_P1280x1.ne0ARCTICne30x4_ne0ARCTICne30x4_mt12.FHIST.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_D_Ln9_Vnuopc_P1280x1.ne0CONUSne30x8_ne0CONUSne30x8_mt12.FCHIST.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_D_Ln9_Vnuopc_P1280x1.ne30pg3_ne30pg3_mg17.FCLTHIST.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_D_Ln9_Vnuopc.T42_T42.FSCAM.derecho_intel.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_Ld1_Vnuopc.f09_f09_mg17.FW2000climo.derecho_intel.cam-outfrq1d (Overall: NLFAIL) details:
+  SMS_Ld1_Vnuopc.f19_f19.F2000dev.derecho_intel.cam-outfrq1d (Overall: NLFAIL) details:
+  SMS_Ld1_Vnuopc.ne30pg3_ne30pg3_mg17.FC2010climo.derecho_intel.cam-outfrq1d (Overall: NLFAIL) details:
+  SMS_Ld5_Vnuopc.f09_f09_mg17.PC6.derecho_intel.cam-cam6_port_f09 (Overall: NLFAIL) details:
+  SMS_Lh12_Vnuopc.f09_f09_mg17.FCSD_HCO.derecho_intel.cam-outfrq3h (Overall: NLFAIL) details:
+  SMS_Ln9_Vnuopc.f09_f09_mg17.F2010climo.derecho_intel.cam-nudging (Overall: NLFAIL) details:
+  SMS_Ln9_Vnuopc.f19_f19.F2000climo.derecho_intel.cam-silhs (Overall: NLFAIL) details:
+- added write_nstep0=.true. to tests
+
+izumi/nag/aux_cam:
+  DAE_Vnuopc.f45_f45_mg37.FHS94.izumi_nag.cam-dae (Overall: FAIL) details:
+- pre-existing failure
+
+  ERC_D_Ln9_Vnuopc.f10_f10_mg37.QPC6.izumi_nag.cam-outfrq3s_cospsathist (Overall: NLFAIL) details:
+  ERC_D_Ln9_Vnuopc.f10_f10_mg37.QPC6.izumi_nag.cam-outfrq3s (Overall: NLFAIL) details:
+  ERC_D_Ln9_Vnuopc.f10_f10_mg37.QPWmaC6.izumi_nag.cam-outfrq3s (Overall: NLFAIL) details:
+  ERC_D_Ln9_Vnuopc.f10_f10_mg37.QSPCAMS.izumi_nag.cam-outfrq3s (Overall: NLFAIL) details:
+  ERS_Ln27_Vnuopc.ne5pg3_ne5pg3_mg37.FKESSLER.izumi_nag.cam-outfrq9s (Overall: NLFAIL) details:
+  ERS_Ln9_Vnuopc.ne5_ne5_mg37.FADIAB.izumi_nag.cam-outfrq9s (Overall: NLFAIL) details:
+  PEM_D_Ln9_Vnuopc.ne5_ne5_mg37.FADIAB.izumi_nag.cam-outfrq3s (Overall: NLFAIL) details:
+  SMS_D_Ln3_Vnuopc.ne5pg3_ne5pg3_mg37.QPX2000.izumi_nag.cam-outfrq3s (Overall: NLFAIL) details:
+  SMS_D_Ln7_Vnuopc.T42_T42_mg17.QPSCAMC5.izumi_nag.cam-scmarm (Overall: NLFAIL) details:
+  SMS_D_Ln9_P1x1_Vnuopc.ne5_ne5_mg37.FADIAB.izumi_nag.cam-outfrq3s (Overall: NLFAIL) details:
+  SUB_D_Ln9_Vnuopc.f10_f10_mg37.QPC5.izumi_nag.cam-outfrq3s (Overall: NLFAIL) details:
+- added write_nstep0=.true. to tests
+
+izumi/gnu/aux_cam:
+  ERC_D_Ln9_Vnuopc.f10_f10_mg37.QPC4.izumi_gnu.cam-outfrq3s_diags (Overall: NLFAIL) details:
+  ERC_D_Ln9_Vnuopc.f10_f10_mg37.QPSPCAMM.izumi_gnu.cam-outfrq3s (Overall: NLFAIL) details:
+  ERC_D_Ln9_Vnuopc.ne5pg2_ne5pg2_mg37.FADIAB.izumi_gnu.cam-outfrq3s (Overall: NLFAIL) details:
+  ERC_D_Ln9_Vnuopc.ne5pg4_ne5pg4_mg37.FADIAB.izumi_gnu.cam-outfrq3s (Overall: NLFAIL) details:
+  ERP_Ln9_Vnuopc.ne5_ne5_mg37.FHS94.izumi_gnu.cam-outfrq9s (Overall: NLFAIL) details:
+  ERP_Ln9_Vnuopc.ne5_ne5_mg37.QPC5.izumi_gnu.cam-outfrq9s (Overall: NLFAIL) details:
+  PEM_D_Ln9_Vnuopc.ne5pg3_ne5pg3_mg37.FADIAB.izumi_gnu.cam-outfrq3s (Overall: NLFAIL) details:
+  SCT_D_Ln7_Vnuopc.T42_T42_mg17.QPC4.izumi_gnu.cam-scm_prep (Overall: NLFAIL) details:
+  SCT_D_Ln7_Vnuopc.T42_T42_mg17.QPC6.izumi_gnu.cam-scm_prep_c6 (Overall: NLFAIL) details:
+  SMS_D_Ln9.f10_f10_mg37.2000_CAM%DEV%GHGMAM4_CLM50%SP_CICE%PRES_DOCN%DOM_MOSART_SGLC_SWAV_SESP.izumi_gnu.cam-outfrq9s (Overall: NLFAIL) details:
+  SMS_D_Ln9_Vnuopc.f10_f10_mg37.QPWmaC4.izumi_gnu.cam-outfrq9s_apmee (Overall: NLFAIL) details:
+  SMS_P48x1_D_Ln9_Vnuopc.f19_f19_mg17.FW4madSD.izumi_gnu.cam-outfrq9s (Overall: NLFAIL) details:
+- added write_nstep0=.true. to tests
+
+CAM tag used for the baseline comparison tests if different than previous
+tag:
+
+Summarize any changes to answers: BFB
+
+===============================================================
+===============================================================
+
 Tag name: cam6_3_140
 Originator(s): peverwhee
 Date: 6 December 2023
@@ -604,6 +767,7 @@ izumi/gnu/aux_cam: All PASS
 
 Summarize any changes to answers: bit-for-bit unchanged
 
+===============================================================
 ===============================================================
 
 Tag name: cam6_3_136

doc/ChangeLog_template

@@ -29,8 +29,6 @@ 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.
 
-cheyenne/intel/aux_cam:
-
 derecho/intel/aux_cam:
 
 izumi/nag/aux_cam:

src/control/cam_history.F90

@@ -167,6 +167,7 @@ module cam_history
   logical :: rgnht(ptapes) = .false.  ! flag array indicating regeneration volumes
   logical :: hstwr(ptapes) = .false.  ! Flag for history writes
   logical :: empty_htapes  = .false.  ! Namelist flag indicates no default history fields
+  logical :: write_nstep0  = .false.  ! write nstep==0 time sample to history files (except monthly)
   logical :: htapes_defined = .false. ! flag indicates history contents have been defined
 
   character(len=cl) :: model_doi_url = '' ! Model DOI
@@ -626,7 +627,7 @@ subroutine history_readnl(nlfile)
 
     ! History namelist items
     namelist /cam_history_nl/ ndens, nhtfrq, mfilt, inithist, inithist_all,    &
-         avgflag_pertape, empty_htapes, lcltod_start, lcltod_stop,             &
+         avgflag_pertape, empty_htapes, write_nstep0, lcltod_start, lcltod_stop,&
          fincl1lonlat, fincl2lonlat, fincl3lonlat, fincl4lonlat, fincl5lonlat, &
          fincl6lonlat, fincl7lonlat, fincl8lonlat, fincl9lonlat,               &
          fincl10lonlat, collect_column_output, hfilename_spec,                 &
@@ -825,8 +826,14 @@ subroutine history_readnl(nlfile)
       end do
     end if ! masterproc
 
-    ! Print per-tape averaging flags
+    ! log output
     if (masterproc) then
+
+      if (write_nstep0) then
+        write(iulog,*)'nstep==0 time sample will be written to all files except monthly average.'
+      end if
+
+      ! Print per-tape averaging flags
       do t = 1, ptapes
         if (avgflag_pertape(t) /= ' ') then
           write(iulog,*)'Unless overridden by namelist input on a per-field basis (FINCL),'
@@ -885,6 +892,7 @@ subroutine history_readnl(nlfile)
     call mpi_bcast(lcltod_stop,  ptapes, mpi_integer, masterprocid, mpicom, ierr)
     call mpi_bcast(collect_column_output, ptapes, mpi_logical, masterprocid, mpicom, ierr)
     call mpi_bcast(empty_htapes,1, mpi_logical, masterprocid, mpicom, ierr)
+    call mpi_bcast(write_nstep0,1, mpi_logical, masterprocid, mpicom, ierr)
     call mpi_bcast(avgflag_pertape, ptapes, mpi_character, masterprocid, mpicom, ierr)
     call mpi_bcast(hfilename_spec, len(hfilename_spec(1))*ptapes, mpi_character, masterprocid, mpicom, ierr)
     call mpi_bcast(fincl, len(fincl (1,1))*pflds*ptapes, mpi_character, masterprocid, mpicom, ierr)
@@ -5585,9 +5593,20 @@ subroutine wshist (rgnht_in)
             hstwr(t) = nstep /= 0 .and. day == 1 .and. ncsec(instantaneous_file_index) == 0
             prev     = .true.
           else
-            hstwr(t) = mod(nstep,nhtfrq(t)) == 0
-            prev     = .false.
-          end if
+            if (nstep == 0) then
+              if (write_nstep0) then
+                hstwr(t) = .true.
+              else
+                ! zero the buffers if nstep==0 data not written
+                do f = 1, nflds(t)
+                  call h_zero(f, t)
+                end do
+              end if
+            else
+              hstwr(t) = mod(nstep,nhtfrq(t)) == 0
+            endif
+            prev = .false.
+           end if
         end if
       end if
       time = ndcur + nscur/86400._r8