Relax tolerance for truncating small snocan values in CanopyFluxes

doc/ChangeLog

@@ -1,4 +1,70 @@
 ===============================================================
+Tag name: ctsm5.2.012
+Originator(s): sacks (Bill Sacks, UCAR/NCAR/CGD)
+Date: Tue 16 Jul 2024 08:57:42 AM MDT
+One-line Summary: Relax tolerance for truncating small snocan values in CanopyFluxes
+
+Purpose and description of changes
+----------------------------------
+
+Details in the PR #2457.
+
+
+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.]
+
+[ ] clm6_0
+
+[ ] clm5_1
+
+[ ] clm5_0
+
+[ ] ctsm5_0-nwp
+
+[ ] clm4_5
+
+
+Bugs fixed
+----------
+List of CTSM issues fixed (include CTSM Issue # and description) [one per line]:
+Fixes #2444 Failing water isotope test on the ctsm5.2 branch
+
+Notes of particular relevance for users
+---------------------------------------
+Changes to documentation: None
+
+Testing summary:
+----------------
+
+ [PASS means all tests PASS; OK means tests PASS other than expected fails.]
+
+  regular tests (aux_clm: https://github.com/ESCOMP/CTSM/wiki/System-Testing-Guide#pre-merge-system-testing):
+
+    derecho ----- OK
+    izumi ------- OK
+
+Answer changes
+--------------
+
+Changes answers relative to baseline:
+ Yes, roundoff.
+
+    - what code configurations: All
+    - what platforms/compilers: All
+    - nature of change: Changes start roundoff level and grow over time.
+
+Other details
+-------------
+Pull Requests that document the changes (include PR ids):
+ https://github.com/ESCOMP/ctsm/pull/2457
+
+===============================================================
+===============================================================
 Tag name: ctsm5.2.011
 Originator(s): slevis (Samuel Levis,UCAR/TSS,303-665-1310)
 Date: Fri 12 Jul 2024 09:45:59 AM MDT

doc/ChangeSum

@@ -1,5 +1,6 @@
 Tag                   Who      Date  Summary
 ============================================================================================================================
+       ctsm5.2.012    sacks 07/16/2024 Relax tolerance for truncating small snocan values in CanopyFluxes
        ctsm5.2.011   slevis 07/12/2024 Merge b4b-dev
        ctsm5.2.010 multiple 07/11/2024 Explicit A/C adoption
        ctsm5.2.009     erik 07/10/2024 Allow for CAM7 in lnd_tuning_mode and handle C or E in long compset names

src/biogeophys/CanopyFluxesMod.F90

@@ -1624,7 +1624,8 @@ subroutine CanopyFluxes(bounds,  num_exposedvegp, filter_exposedvegp,
       ! snocan < rel_epsilon * snocan_baseline will be set to zero
       ! See NumericsMod for rel_epsilon value
       call truncate_small_values(fn, filterp, begp, endp, &
-         snocan_baseline(begp:endp), snocan(begp:endp))
+         snocan_baseline(begp:endp), snocan(begp:endp), &
+         custom_rel_epsilon=1.e-10_r8)
 
       if ( use_fates ) then