Merge branch 'no_dynlu_first_step'

Avoid glacier dynamic landunit adjustments in first time step

Always avoid generating dynamic landunit adjustments for glacier area
changes in the first timestep of a startup or hybrid run - not just for
cold start or interpolated start. See the detailed discussion in
#340 for rationale.

Merges PR #470

Fixes #340

doc/ChangeLog

@@ -1,4 +1,152 @@
 ===============================================================
+Tag name:  ctsm1.0.dev007
+Originator(s):  sacks (Bill Sacks)
+Date: Sun Aug  5 21:03:28 MDT 2018
+One-line Summary: Avoid glacier dynamic landunit adjustments in first time step
+
+Purpose of changes
+------------------
+
+Always avoid generating dynamic landunit adjustments for glacier area
+changes in the first timestep of a startup or hybrid run - not just for
+cold start or interpolated start. See the detailed discussion in
+https://github.com/ESCOMP/ctsm/issues/340 for rationale.
+
+
+Bugs fixed or introduced
+------------------------
+
+Issues fixed (include CTSM Issue #):
+- Fixes #340 (Avoid generating dynamic landunit adjustment fluxes for
+  glacier changes in the first timestep)
+
+
+Significant changes to scientifically-supported configurations
+--------------------------------------------------------------
+
+Does this tag change answers significantly for any of the following physics configurations?
+(Details of any changes will be given in the "Answer changes" section below.)
+
+    [Put an [X] in the box for any configuration with significant answer changes.]
+
+[ ] clm5_0
+
+[ ] clm4_5
+
+[ ] clm4_0
+
+Notes of particular relevance for users
+---------------------------------------
+
+Caveats for users (e.g., need to interpolate initial conditions): none
+
+Changes to CTSM's user interface (e.g., new/renamed XML or namelist variables): none
+
+Changes made to namelist defaults (e.g., changed parameter values): none
+
+Changes to the datasets (e.g., parameter, surface or initial files): none
+
+Substantial timing or memory changes: none
+
+Notes of particular relevance for developers: (including Code reviews and testing)
+---------------------------------------------
+NOTE: Be sure to review the steps in .CTSMTrunkChecklist as well as the coding style in the Developers Guide
+
+Caveats for developers (e.g., code that is duplicated that requires double maintenance): none
+
+Changes to tests or testing: none
+
+Code reviewed by: Erik Kluzek
+
+
+CTSM testing:
+
+ [PASS means all tests PASS and OK means tests PASS other than expected fails.]
+
+  build-namelist tests:
+
+    cheyenne - not run
+
+  unit-tests (components/clm/src):
+
+    cheyenne - not run
+
+  tools-tests (components/clm/test/tools):
+
+    cheyenne - not run
+
+  PTCLM testing (components/clm/tools/shared/PTCLM/test):
+
+     cheyenne - not run
+
+  regular tests (aux_clm):
+
+    cheyenne_intel ---- ok
+    cheyenne_gnu ------ pass
+    hobart_nag -------- pass
+    hobart_pgi -------- pass
+    hobart_intel ------ pass
+
+    ok means tests pass; baseline failures as expected in these two
+    tests that do not use init_interp:
+
+    FAIL ERI_N2_Ld9.f19_g17.I2000Clm50BgcCrop.cheyenne_intel.clm-default BASELINE ctsm1.0.dev006
+    FAIL SMS_Lm13.f19_g17.I2000Clm50BgcCrop.cheyenne_intel.clm-cropMonthOutput BASELINE ctsm1.0.dev006
+
+    (The glacier area on the finidat file used in these tests -
+    clmi.I2000Clm50BgcCrop.2011-01-01.1.9x2.5_gx1v7_gl4_simyr2000_c180715.nc
+    - seems to have come from an finidat_interp_dest file, and thus does
+    not match the glacier area from CISM.)
+
+CTSM tag used for the baseline comparisons: ctsm1.0.dev006
+
+
+Answer changes
+--------------
+
+Changes answers relative to baseline: YES
+
+  If a tag changes answers relative to baseline comparison the
+  following should be filled in (otherwise remove this section):
+
+  Summarize any changes to answers, i.e.,
+    - what code configurations: Startup / Hybrid runs that include CISM
+     (even NOEVOLVE) and do not use init_interp, due to:
+     - different PE layout in new case vs. the one that generated the
+       finidat (roundoff-level diffs)
+     - different glacier area on finidat file vs. what's in CISM
+       (greater than roundoff-level diffs)
+    - what platforms/compilers: all
+    - nature of change (roundoff; larger than roundoff/same climate; new climate): 
+      Roundoff-level for different PE layout, larger than roundoff but
+      should be same climate when there is different glacier area on the
+      finidat file vs. what's in CISM
+
+      The differences arise from dynamic landunit adjustments of the
+      below-ground C and N states in the old code, as CTSM adjusts its
+      areas to match CISM's. In the new code, there are no C and N
+      adjustments in the first time step from this adjustment.
+
+   If bitwise differences were observed, how did you show they were no worse
+   than roundoff? N/A
+
+   If this tag changes climate describe the run(s) done to evaluate the new
+   climate (put details of the simulations in the experiment database)
+       - casename: N/A
+
+   URL for LMWG diagnostics output used to validate new climate: N/A
+
+
+Detailed list of changes
+------------------------
+
+List any externals directories updated (cime, rtm, mosart, cism, fates, etc.): none
+
+Pull Requests that document the changes (include PR ids):
+- #470 (Avoid glacier dynamic landunit adjustments in first time step)
+
+===============================================================
+===============================================================
 Tag name:  ctsm1.0.dev006
 Originator(s):  sacks (Bill Sacks)
 Date: Sat Aug  4 07:48:09 MDT 2018

doc/ChangeSum

@@ -1,5 +1,6 @@
 Tag                   Who      Date  Summary
 ============================================================================================================================
+  ctsm1.0.dev007    sacks 08/05/2018 Avoid glacier dynamic landunit adjustments in first time step
   ctsm1.0.dev006    sacks 08/04/2018 Minor bug fixes, cleanup, documentation and enhancements
   ctsm1.0.dev005    sacks 08/03/2018 Rework water data types to accommodate isotopes and other tracers
   ctsm1.0.dev004     erik 07/18/2018 Add some new diagnostic fields, fix a few issues, update cmip6 output

src/main/clm_driver.F90

@@ -12,7 +12,6 @@ module clm_driver
   use clm_varctl             , only : wrtdia, iulog, use_fates
   use clm_varctl             , only : use_cn, use_lch4, use_noio, use_c13, use_c14
   use clm_varctl             , only : use_crop, ndep_from_cpl
-  use clm_varctl             , only : is_cold_start, is_interpolated_start
   use clm_time_manager       , only : get_nstep, is_beg_curr_day
   use clm_time_manager       , only : get_prev_date, is_first_step
   use clm_varpar             , only : nlevsno, nlevgrnd
@@ -166,14 +165,19 @@ subroutine clm_drv(doalb, nextsw_cday, declinp1, declin, rstwr, nlend, rdate, ro
     nclumps = get_proc_clumps()
 
     ! ========================================================================
-    ! In the first time step of a run that used cold start or init_interp, glacier areas
-    ! will start at whatever is specified on the surface dataset, because coupling fields
-    ! from GLC aren't received until the run loop. Thus, CLM will see a potentially large,
-    ! fictitious glacier area change in the first time step after cold start or
-    ! init_interp. We don't want this fictitious area change to result in any state or
-    ! flux adjustments. Thus, we apply this area change here, at the start of the driver
-    ! loop, so that in dynSubgrid_driver, it will look like there is no glacier area
-    ! change in the first time step.
+    ! In the first time step of a startup or hybrid run, we want to update CLM's glacier
+    ! areas to match those given by GLC. This is because, in initialization, we do not yet
+    ! know GLC's glacier areas, so CLM's glacier areas are based on the surface dataset
+    ! (for a cold start or init_interp run) or the initial conditions file (in a
+    ! non-init_interp, non-cold start run) - which may not match GLC's glacier areas for
+    ! this configuration. (Coupling fields from GLC aren't received until the run loop.)
+    ! Thus, CLM will see a potentially large, fictitious glacier area change in the first
+    ! time step. We don't want this fictitious area change to result in any state or flux
+    ! adjustments. Thus, we apply this area change here, at the start of the driver loop,
+    ! so that in dynSubgrid_driver, it will look like there is no glacier area change in
+    ! the first time step. (See
+    ! https://github.com/ESCOMP/ctsm/issues/340#issuecomment-410483131 for more
+    ! discussion on this.)
     !
     ! This needs to happen very early in the run loop, before any balance checks are
     ! initialized, because - by design - this doesn't conserve mass at the grid cell
@@ -197,8 +201,7 @@ subroutine clm_drv(doalb, nextsw_cday, declinp1, declin, rstwr, nlend, rdate, ro
     ! are passed to CLM in initialization, then this code block can be removed.
     ! ========================================================================
 
-    need_glacier_initialization = (is_first_step() .and. &
-         (is_cold_start .or. is_interpolated_start))
+    need_glacier_initialization = is_first_step()
 
     if (need_glacier_initialization) then
        !$OMP PARALLEL DO PRIVATE (nc, bounds_clump)