Expose finer-grained control over physics subroutines (#7)

This PR ports the changes in ai2cm/fv3gfs-fortran#317 to the SHiELD wrapper, which give us finer grained control over the steps of the time loop related to the physics.

It depends on NOAA-GFDL/atmos_drivers#30, which was merged upstream and incorporated into this repository in #11.

wrapper/lib/coupler_lib.F90

@@ -31,7 +31,12 @@ module coupler_lib
                                update_atmos_model_dynamics,        &
                                update_atmos_radiation_physics,     &
                                update_atmos_model_state,           &
-                               atmos_data_type, atmos_model_restart
+                               atmos_data_type,                    &
+                               atmos_model_restart,                &
+                               update_atmos_pre_radiation,         &
+                               update_atmos_radiation,             &
+                               update_atmos_physics
+
     !--- FMS old io
 #ifdef use_deprecated_io
     use fms_io_mod, only: fms_io_exit!< This can't be removed until fms_io is not used at all
@@ -194,12 +199,20 @@ subroutine do_dynamics() bind(c)
         Time_atmos = Time_atmos + Time_step_atmos
         call update_atmos_model_dynamics (Atm)
     end subroutine do_dynamics
+
+  ! substepped physics
+    subroutine do_pre_radiation() bind(c)
+        call update_atmos_pre_radiation (Atm)
+    end subroutine do_pre_radiation
+
+    subroutine do_radiation() bind(c)
+        call update_atmos_radiation (Atm)
+    end subroutine do_radiation
 
     subroutine do_physics() bind(c)
-        call update_atmos_radiation_physics (Atm)
-        call update_atmos_model_state (Atm)
+        call update_atmos_physics (Atm)
     end subroutine do_physics
-    
+
     subroutine compute_physics_subroutine() bind(c)
         call update_atmos_radiation_physics (Atm)
     end subroutine compute_physics_subroutine

wrapper/shield/wrapper/__init__.py

@@ -5,6 +5,9 @@
     initialize,
     step,
     step_dynamics,
+    step_radiation,
+    step_pre_radiation,
+    step_post_radiation_physics,
     step_physics,
     save_intermediate_restart_if_enabled,
     save_fortran_restart,

wrapper/templates/_wrapper.pyx

@@ -561,6 +561,28 @@ def _get_diagnostic_data(int idx):
     return pace.util.Quantity(array, dims, units=units)
 
 
+cdef extern:
+    void do_pre_radiation()
+    void do_radiation()
+    void do_physics()
+
+
+def step_pre_radiation():
+    """Do pre-radiation computations (e.g. time varying logic)"""
+    do_pre_radiation()
+
+
+def step_radiation():
+    """Compute Radiative transfer scheme"""
+    do_radiation()
+
+
+def step_post_radiation_physics():
+    """Compute Post-radiation physics (e.g. moist physics turbulence)"""
+    # TODO ensure that IPD_control.first_step is set in this routine
+    do_physics()
+
+
 def transform_agrid_winds_to_dgrid_winds(ua, va):
     """Transform A-grid lat-lon winds to D-grid cubed-sphere winds.
     This function wraps the cubed_a2d subroutine from the fortran model, making