Add use_climatological_sst namelist flag (#173)

This must be set to `.false.` if one would like to override the SST from within the Python wrapper.

FV3/gfsphysics/GFS_layer/GFS_physics_driver.F90

@@ -674,6 +674,7 @@ subroutine GFS_physics_driver                                 &
       real(kind=kind_phys), allocatable, dimension(:,:) :: den
       real(kind=kind_phys), allocatable, dimension(:,:) :: dqdt_work
       real(kind=kind_phys), pointer :: adjsfcdlw_for_lsm(:), adjsfcdsw_for_lsm(:), adjsfcnsw_for_lsm(:)
+      real(kind=kind_phys), pointer :: sea_surface_temperature(:)
       integer :: nwat
 
       !! Initialize local variables (mainly for debugging purposes, because the
@@ -728,6 +729,11 @@ subroutine GFS_physics_driver                                 &
         adjsfcnsw_for_lsm => adjsfcnsw
       endif
 
+      if (Model%use_climatological_sst) then
+        sea_surface_temperature => Sfcprop%tsfc
+      else
+        sea_surface_temperature => Sfcprop%tsfco
+      endif
 !-------
 ! For COORDE-2019 averaging with fwindow, it was done before
 ! 3Diag fixes and averaging ingested using "fdaily"-factor
@@ -1129,7 +1135,7 @@ subroutine GFS_physics_driver                                 &
         do i = 1, IM
           frland(i) = zero
           if (islmsk(i) == 0) then
-            Sfcprop%tsfco(i) = Sfcprop%tsfc(i)
+            Sfcprop%tsfco(i) = sea_surface_temperature(i)
             wet(i)  = .true.
             fice(i) = zero
           elseif (islmsk(i) == 1) then

FV3/gfsphysics/GFS_layer/GFS_typedefs.F90

@@ -1084,6 +1084,7 @@ module GFS_typedefs
     logical :: iau_filter_increments
     real(kind=kind_phys) :: sst_perturbation  ! Sea surface temperature perturbation to climatology or nudging SST (default 0.0 K)
     logical :: override_surface_radiative_fluxes  ! Whether to use Statein to override the surface radiative fluxes
+    logical :: use_climatological_sst  ! Whether to allow the Python wrapper to override the sea surface temperature
 #ifdef CCPP
     ! From physcons.F90, updated/set in control_initialize
     real(kind=kind_phys) :: dxinv           ! inverse scaling factor for critical relative humidity, replaces dxinv in physcons.F90
@@ -3128,6 +3129,7 @@ subroutine control_initialize (Model, nlunit, fn_nml, me, master, &
 
     real(kind=kind_phys) :: sst_perturbation = 0.0  ! Sea surface temperature perturbation [K]
     logical :: override_surface_radiative_fluxes = .false.
+    logical :: use_climatological_sst = .true.
 !--- END NAMELIST VARIABLES
 
     NAMELIST /gfs_physics_nml/                                                              &
@@ -3219,7 +3221,7 @@ subroutine control_initialize (Model, nlunit, fn_nml, me, master, &
                           !--- aerosol scavenging factors ('name:value' string array)
                                fscav_aero, &
                                sst_perturbation,                                            & 
-                               override_surface_radiative_fluxes
+                               override_surface_radiative_fluxes, use_climatological_sst
 
 !--- other parameters 
     integer :: nctp    =  0                !< number of cloud types in CS scheme
@@ -3688,6 +3690,7 @@ subroutine control_initialize (Model, nlunit, fn_nml, me, master, &
 
     Model%sst_perturbation = sst_perturbation
     Model%override_surface_radiative_fluxes = override_surface_radiative_fluxes
+    Model%use_climatological_sst = use_climatological_sst
 !--- tracer handling
     Model%ntrac            = size(tracer_names)
 #ifdef CCPP
@@ -4496,6 +4499,7 @@ subroutine control_print(Model)
       print *, ' isot              : ', Model%isot
       print *, ' sst_perturbation  : ', Model%sst_perturbation
       print *, ' override_surface_radiative_fluxes: ', Model%override_surface_radiative_fluxes
+      print *, ' use_climatological_sst: ', Model%use_climatological_sst
       if (Model%lsm == Model%lsm_noahmp) then
       print *, ' Noah MP LSM is used, the options are'
       print *, ' iopt_dveg         : ', Model%iopt_dveg