Merge pull request ESCOMP#1100 from brian-eaton/rrtmgp-mt

cam6_4_016: Modify RRTMGP interface for MT configurations.

.gitmodules

@@ -57,7 +57,7 @@
 [submodule "hemco"]
 	path = src/hemco
 	url = https://github.com/ESCOMP/HEMCO_CESM.git
-        fxtag = hemco-cesm1_2_1_hemco3_6_3_cesm_rme
+        fxtag = hemco-cesm1_2_1_hemco3_6_3_cesm_rme01
         fxrequired = AlwaysRequired
 	fxDONOTUSEurl = https://github.com/ESCOMP/HEMCO_CESM.git
 

doc/ChangeLog

@@ -1,5 +1,94 @@
 ===============================================================
 
+Tag name: cam6_4_016
+Originator(s): brianpm, eaton
+Date: 25 July 2024
+One-line Summary: Modify RRTMGP interface for MT configurations.
+Github PR URL: https://github.com/ESCOMP/CAM/pull/1100
+
+Purpose of changes (include the issue number and title text for each relevant GitHub issue):
+
+Issue #1063 - Possible modification to RRTMG-P for ~80km top model
+. Modify the RRTMGP interface for the special case when the minimum valid
+  pressure for RRTMGP (1 Pa) falls in the top model layer (as it does in
+  CAM's 93 level MT configuration). The modification is to use the "extra
+  layer" code path, and add a very thin extra layer just below 1 Pa. The
+  algorithm to calculate the midpoint pressure in the "extra layer" has
+  changed from the original (which assumed a model top at 0 Pa). Hence the
+  change affects answers for the low top model configurations (cam7-LT and cam6)
+  as well as the cam7-MT configuration.
+
+  Note that this modification is still being tested for scientific validity
+  in the cam7-MT configuration. 
+
+Issue #1097 - HEMCO reference in .gitmodules is a branch not a tag.
+. Modify .gitmodules to resolve #1097
+
+Describe any changes made to build system: none
+
+Describe any changes made to the namelist: none
+
+List any changes to the defaults for the boundary datasets: none
+
+Describe any substantial timing or memory changes: none
+
+Code reviewed by: cacraig
+
+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:
+
+.gitmodules
+- hemco-cesm1_2_1_hemco3_6_3_cesm_rme => hemco-cesm1_2_1_hemco3_6_3_cesm_rme01
+
+src/physics/rrtmgp/radiation.F90
+src/physics/rrtmgp/rrtmgp_inputs.F90
+. Identify special case of 1 Pa pressure level being contained in the top
+  model layer.  Treat that case as though an "extra layer" is needed, and
+  add a very thin extra layer just below 1 Pa.
+
+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_D_Ln9.ne30pg3_ne30pg3_mg17.FLTHIST.derecho_intel.cam-outfrq9s_rrtmgp (Overall: DIFF) details:
+- diffs due to change in RRTMGP interface
+
+ERP_Ln9.f09_f09_mg17.FCSD_HCO.derecho_intel.cam-outfrq9s (Overall: FAIL) details:
+- pre-existing failure due to HEMCO not having reproducible results issues #1018 and #856
+
+SMS_D_Ln9_P1280x1.ne0ARCTICne30x4_ne0ARCTICne30x4_mt12.FHIST.derecho_intel.cam-outfrq9s (Overall: PEND) details:
+SMS_D_Ln9_P1280x1.ne0CONUSne30x8_ne0CONUSne30x8_mt12.FCHIST.derecho_intel.cam-outfrq9s (Overall: PEND) details:
+- pre-existing failures -- need fix in CLM external
+
+SMS_D_Ln9.T42_T42.FSCAM.derecho_intel.cam-outfrq9s (Overall: FAIL) details:
+- pre-existing failure -- need fix in CICE external
+
+izumi/nag/aux_cam:
+
+DAE.f45_f45_mg37.FHS94.izumi_nag.cam-dae (Overall: FAIL) details:
+- pre-existing failure - issue #670
+
+izumi/gnu/aux_cam:
+
+ERP_D_Ln9.ne3pg3_ne3pg3_mg37.QPC6.izumi_gnu.cam-outfrq9s_rrtmgp (Overall: DIFF)
+SMS_Ld5.f09_f09_mg17.PC6.izumi_gnu.cam-cam6_port_f09_rrtmgp (Overall: DIFF)
+- diffs due to change in RRTMGP interface
+
+CAM tag used for the baseline comparison tests if different than previous
+tag:
+
+Summarize any changes to answers: BFB except answer changes expected for
+configurations using cam7MT, cam7LT, and cam6 with RRTMGP
+
+===============================================================
+===============================================================
+
 Tag name: cam6_4_015
 Originator(s): jedwards, eaton
 Date: 23 July 2024

src/physics/rrtmgp/radiation.F90

@@ -453,6 +453,7 @@ subroutine radiation_init(pbuf2d)
    ! pressure interfaces below 1 Pa.  When the entire model atmosphere is
    ! below 1 Pa then an extra layer is added to the top of the model for
    ! the purpose of the radiation calculation.
+
    nlay = count( pref_edge(:) > 1._r8 ) ! pascals (0.01 mbar)
 
    if (nlay == pverp) then
@@ -461,14 +462,22 @@ subroutine radiation_init(pbuf2d)
       ktopcam = 1
       ktoprad = 2
       nlaycam = pver
+   else if (nlay == (pverp-1)) then
+      ! Special case nlay == (pverp-1) -- topmost interface outside bounds (CAM MT config), treat as if it is ok.
+      ktopcam = 1
+      ktoprad = 2
+      nlaycam = pver
+      nlay = nlay+1 ! reassign the value so later code understands to treat this case like nlay==pverp
+      write(iulog,*) 'RADIATION_INIT: Special case of 1 model interface at p < 1Pa. Top layer will be INCLUDED in radiation calculation.'
+      write(iulog,*) 'RADIATION_INIT: nlay = ',nlay, ' same as pverp: ',nlay==pverp
    else
       ! nlay < pverp.  nlay layers are used in radiation calcs, and they are
       ! all CAM layers.
       ktopcam = pver - nlay + 1
       ktoprad = 1
       nlaycam = nlay
    end if
-
+   
    ! Create lowercase version of the gaslist for RRTMGP.  The ty_gas_concs objects
    ! work with CAM's uppercase names, but other objects that get input from the gas
    ! concs objects don't work.

src/physics/rrtmgp/rrtmgp_inputs.F90

@@ -150,11 +150,20 @@ subroutine rrtmgp_set_state( &
 
    ! Add extra layer values if needed.
    if (nlay == pverp) then
-      t_rad(:,1)      = state%t(:ncol,1)
-      pmid_rad(:,1)   = 0.5_r8 * state%pint(:ncol,1)
+      t_rad(:,1) = state%t(:ncol,1)
       ! The top reference pressure from the RRTMGP coefficients datasets is 1.005183574463 Pa
       ! Set the top of the extra layer just below that.
       pint_rad(:,1) = 1.01_r8
+
+      ! next interface down in LT will always be > 1Pa
+      ! but in MT we apply adjustment to have it be 1.02 Pa if it was too high
+      where (pint_rad(:,2) <= pint_rad(:,1)) pint_rad(:,2) = pint_rad(:,1)+0.01_r8
+
+      ! set the highest pmid (in the "extra layer") to the midpoint (guarantees > 1Pa) 
+      pmid_rad(:,1)   = pint_rad(:,1) + 0.5_r8 * (pint_rad(:,2) - pint_rad(:,1))
+
+      ! For case of CAM MT, also ensure pint_rad(:,2) > pint_rad(:,1) & pmid_rad(:,2) > max(pmid_rad(:,1), min_pressure)
+      where (pmid_rad(:,2) <= kdist_sw%get_press_min()) pmid_rad(:,2) = pint_rad(:,2) + 0.01_r8
    else
       ! nlay < pverp, thus the 1 Pa level is within a CAM layer.  Assuming the top interface of
       ! this layer is at a pressure < 1 Pa, we need to adjust the top of this layer so that it