Improve documentation of nextsw_cday_calc and iradsw

datm/atm_comp_nuopc.F90

@@ -885,15 +885,14 @@ end subroutine datm_comp_run
   real(R8) function getNextRadCDay( julday, tod, stepno, dtime, iradsw )
 
     ! Return the calendar day of the next radiation time-step.
-    ! General Usage: nextswday = getNextRadCDay(curr_date) iradsw is
-    ! the frequency to update the next shortwave.  in number of steps
-    ! (or hours if negative) Julian date.
-    ! -- values greater than 1 set
-    !    the next radiation to the present time plus 2 timesteps every iradsw
-    ! -- values less than 0 turn set the next radiation to the  present time
-    !    plus two timesteps every -iradsw hours.
-    ! -- if iradsw is zero, the next radiation time is the
-    !    present time plus 1 timestep.
+    ! General Usage: nextswday = getNextRadCDay(curr_date). iradsw is
+    ! the frequency to update the next shortwave in number of steps
+    ! (or hours if negative).
+    ! -- values greater than 1 set the next radiation to the present time plus either 1 or
+    !    2 timesteps (depending on the value of nextsw_cday_calc_cam7) every iradsw timesteps.
+    ! -- values less than 0 set the next radiation to the present time plus either 1 or 2
+    !    timesteps (depending on the value of nextsw_cday_calc_cam7) every -iradsw hours.
+    ! -- if iradsw is either 0 or 1, the next radiation time is the present time plus 1 timestep.
 
     ! input/output variables
     real(r8)    , intent(in) :: julday

datm/cime_config/namelist_definition_datm.xml

@@ -332,13 +332,15 @@
     <category>datm</category>
     <group>datm_nml</group>
     <desc>
-      Frequency to update radiation in number of steps (or hours if negative)
-      irdasw is the radiation setting used to compute the next shortwave
-      Julian date.  values greater than 1 set the next radiation to the
-      present time plus 2 timesteps every iradsw.  values less than 0 turn
-      set the next radiation to the present time plus two timesteps every
-      -iradsw hours.  if iradsw is zero, the next radiation time is the
-      present time plus 1 timestep.  (default=0.)
+      Frequency to update radiation in number of steps (or hours if negative).
+
+      irdasw is the radiation setting used to compute the next shortwave Julian date.
+      Values greater than 1 set the next radiation to the present time plus either 1 or 2
+      timesteps (depending on the value of nextsw_cday_calc) every iradsw timesteps.
+      Values less than 0 set the next radiation to the present time plus either 1 or 2
+      timesteps (depending on the value of nextsw_cday_calc) every -iradsw hours. If
+      iradsw is either 0 or 1, the next radiation time is the present time plus 1
+      timestep. (default=1 for non-CPLHIST cases, and -1 for CPLHIST cases.)
     </desc>
     <values>
       <value>1</value>
@@ -352,13 +354,18 @@
     <group>datm_nml</group>
     <valid_values>cam6,cam7</valid_values>
     <desc>
-      Logic to use for calculating nextsw_cday. For CPLHIST cases, this should agree with
-      the version of CAM (or other atmosphere model) used to generate the CPLHIST
-      forcings; the valid values for this variable are based on this: 'cam6' is
-      appropriate for cases generated with the driver ordering in CAM6 and earlier, and
-      'cam7' is appropriate for cases generated with the driver ordering in CAM7 and
-      later. This variable also applies for non-CPLHIST cases, but we currently assume (by
-      default) that non-CPLHIST cases follow the logic that was used in CAM6 and earlier.
+      Logic to use for calculating nextsw_cday. This variable has no effect when iradsw is
+      0 or 1, so by default this only applies in CPLHIST cases.
+
+      For CPLHIST cases, this should agree with the version of CAM (or other atmosphere
+      model) used to generate the CPLHIST forcings; the valid values for this variable are
+      based on this: 'cam6' is appropriate for cases generated with the driver ordering in
+      CAM6 and earlier, and 'cam7' is appropriate for cases generated with the driver
+      ordering in CAM7 and later.
+
+      For 'cam6', the next radiation timestep is set to the present time plus 2 timesteps
+      when mod(tod+dtime,delta_radsw)==0. For 'cam7', the next radiation timestep is set
+      to the present time plus 1 timestep when mod(tod,delta_radsw)==0.
     </desc>
     <values>
       <value>cam6</value>