Merge pull request #481 from billsacks/remove_negative_runoff_land_only

Separate the control of removing negative runoff for lnd vs glc, and set default to false for glc-derived runoff

### Description of changes

This is a follow-up to #471 .

At least for now, we want the default to be to remove negative runoff for lnd-derived runoff, but NOT for glc-derived runoff. This PR implements that change. Note that this changes behavior for the correction of glc-derived runoff, but keeps the behavior the same as before for lnd-derived runoff.

### Specific notes

Are changes expected to change answers? (specify if bfb, different at roundoff, more substantial): **Yes - changes answers substantially for runoff fields in some B compsets (or other configurations with both active land/river and active ocean) - but only for configurations that have glc-derived runoff; this can currently come from configurations with CISM in EVOLVE mode or DGLC (even in NOEVOLVE mode). Note that this change just undoes part of the answer changes that came from #471 .**

Any User Interface Changes (namelist or namelist defaults changes)? Separates the namelist item remove_negative_runoff into two separate options: remove_negative_runoff_lnd and remove_negative_runoff_glc.

### Testing performed
Please describe the tests along with the target model and machine(s) 
If possible, please also added hashes that were used in the testing

Using `cesm2_3_beta17` (with CISM at `756cfa6f0514d89977d2732ad06a4d364da5d418`, mosart at mosart1.1.02, and removing the contents of `cime_config/testmods_dirs/allactive/defaultio/user_nl_mosart`: Ran three versions of `SMS_D_Ld3.f19_g17.B1850G.derecho_intel.allactive-cism-test_coupling`:
- One with default flags
- One with `remove_negative_runoff_glc` set to true
- One with `remove_negative_runoff_lnd` set to false

I checked the behavior in these in runs with dbug_flag set to 21 so I would see diagnostics of what fields were being adjusted, and confirmed that the correct fields were being operated on in all three cases.

cime_config/namelist_definition_drv.xml

@@ -872,17 +872,28 @@
       <value COMP_LND="xlnd">off</value>
     </values>
   </entry>
-  <entry id="remove_negative_runoff">
+  <entry id="remove_negative_runoff_lnd">
     <type>logical</type>
     <category>control</category>
     <group>MED_attributes</group>
     <desc>
-      If true, remove negative runoff by downweighting all positive runoff globally.
+      If true, remove negative runoff generated from the land component by downweighting all positive runoff globally.
     </desc>
     <values>
       <value>.true.</value>
     </values>
   </entry>
+  <entry id="remove_negative_runoff_glc">
+    <type>logical</type>
+    <category>control</category>
+    <group>MED_attributes</group>
+    <desc>
+      If true, remove negative runoff generated from the glc (ice sheet) component by downweighting all positive runoff globally.
+    </desc>
+    <values>
+      <value>.false.</value>
+    </values>
+  </entry>  
 
   <entry id="info_debug" modify_via_xml="INFO_DBUG">
     <type>integer</type>

mediator/med_phases_post_rof_mod.F90

@@ -38,14 +38,16 @@ module med_phases_post_rof_mod
   integer :: num_rof_fields
   character(len=CS), allocatable :: rof_field_names(:)
 
-  logical :: remove_negative_runoff
-
-  character(len=13), parameter :: fields_to_remove_negative_runoff(4) = &
-       ['Forr_rofl    ', &
-        'Forr_rofi    ', &
-        'Forr_rofl_glc', &
+  logical :: remove_negative_runoff_lnd
+  logical :: remove_negative_runoff_glc
+
+  character(len=9), parameter :: fields_to_remove_negative_runoff_lnd(2) = &
+       ['Forr_rofl', &
+        'Forr_rofi']
+  character(len=13), parameter :: fields_to_remove_negative_runoff_glc(2) = &
+       ['Forr_rofl_glc', &
         'Forr_rofi_glc']
-
+ 
   character(*) , parameter :: u_FILE_u = &
        __FILE__
 
@@ -77,12 +79,20 @@ subroutine med_phases_post_rof_init(gcomp, rc)
     call med_phases_post_rof_create_rof_field_bundle(gcomp, rc)
     if (ChkErr(rc,__LINE__,u_FILE_u)) return
 
-    call NUOPC_CompAttributeGet(gcomp, name='remove_negative_runoff', value=cvalue, isPresent=isPresent, isSet=isSet, rc=rc)
+    call NUOPC_CompAttributeGet(gcomp, name='remove_negative_runoff_lnd', value=cvalue, isPresent=isPresent, isSet=isSet, rc=rc)
+    if (chkerr(rc,__LINE__,u_FILE_u)) return
+    if (isPresent .and. isSet) then
+      read(cvalue,*) remove_negative_runoff_lnd
+    else
+      remove_negative_runoff_lnd = .false.
+    end if
+
+    call NUOPC_CompAttributeGet(gcomp, name='remove_negative_runoff_glc', value=cvalue, isPresent=isPresent, isSet=isSet, rc=rc)
     if (chkerr(rc,__LINE__,u_FILE_u)) return
     if (isPresent .and. isSet) then
-      read(cvalue,*) remove_negative_runoff
+      read(cvalue,*) remove_negative_runoff_glc
     else
-      remove_negative_runoff = .false.
+      remove_negative_runoff_glc = .false.
     end if
 
     ! remove_negative_runoff isn't yet set up to handle isotope fields, so ensure that
@@ -94,12 +104,13 @@ subroutine med_phases_post_rof_init(gcomp, rc)
     else
        flds_wiso = .false.
     end if
-    if (remove_negative_runoff .and. flds_wiso) then
-      call shr_sys_abort('remove_negative_runoff must be set to false when flds_wiso is true')
+    if ((remove_negative_runoff_lnd .or. remove_negative_runoff_glc) .and. flds_wiso) then
+      call shr_sys_abort('remove_negative_runoff_lnd and remove_negative_runoff_glc must be set to false when flds_wiso is true')
     end if
 
     if (maintask) then
-      write(logunit,'(a,l7)') trim(subname)//' remove_negative_runoff = ', remove_negative_runoff
+      write(logunit,'(a,l7)') trim(subname)//' remove_negative_runoff_lnd = ', remove_negative_runoff_lnd
+      write(logunit,'(a,l7)') trim(subname)//' remove_negative_runoff_glc = ', remove_negative_runoff_glc
     end if
 
     if (dbug_flag > 20) then
@@ -143,12 +154,22 @@ subroutine med_phases_post_rof(gcomp, rc)
       data_copy(:) = data_orig(:)
     end do
 
-    if (remove_negative_runoff) then
-      do n = 1, size(fields_to_remove_negative_runoff)
-        call ESMF_FieldBundleGet(FBrof_r, fieldName=trim(fields_to_remove_negative_runoff(n)), isPresent=exists, rc=rc)
+    if (remove_negative_runoff_lnd) then
+      do n = 1, size(fields_to_remove_negative_runoff_lnd)
+        call ESMF_FieldBundleGet(FBrof_r, fieldName=trim(fields_to_remove_negative_runoff_lnd(n)), isPresent=exists, rc=rc)
+        if (ChkErr(rc,__LINE__,u_FILE_u)) return
+        if (exists) then
+          call med_phases_post_rof_remove_negative_runoff(gcomp, fields_to_remove_negative_runoff_lnd(n), rc)
+          if (ChkErr(rc,__LINE__,u_FILE_u)) return
+        end if
+      end do
+    end if
+    if (remove_negative_runoff_glc) then
+      do n = 1, size(fields_to_remove_negative_runoff_glc)
+        call ESMF_FieldBundleGet(FBrof_r, fieldName=trim(fields_to_remove_negative_runoff_glc(n)), isPresent=exists, rc=rc)
         if (ChkErr(rc,__LINE__,u_FILE_u)) return
         if (exists) then
-          call med_phases_post_rof_remove_negative_runoff(gcomp, fields_to_remove_negative_runoff(n), rc)
+          call med_phases_post_rof_remove_negative_runoff(gcomp, fields_to_remove_negative_runoff_glc(n), rc)
           if (ChkErr(rc,__LINE__,u_FILE_u)) return
         end if
       end do