[Dart-dev] DART/branches Revision: 13063

[dart at ucar.edu]

raeder at ucar.edu
2019-03-25 14:26:30 -0600 (Mon, 25 Mar 2019)
148
Updated guidance about handling the top layers of CAM and WACCM,
where extra diffusion may be applied and assimilation should probably not be done.



Modified: DART/branches/recam/models/cam-fv/work/input.nml
===================================================================
--- DART/branches/recam/models/cam-fv/work/input.nml	2019-03-25 19:40:49 UTC (rev 13062)
+++ DART/branches/recam/models/cam-fv/work/input.nml	2019-03-25 20:26:30 UTC (rev 13063)
@@ -103,8 +103,9 @@
 ! Creation of initial ensemble from a single model state.
 !     fields_to_perturb lists the state variables to be perturbed to make the ensemble.
 !         Providing an empty list is one of the changes to use an existing ensemble.
-!     perturbation_amplitude > 0 allows each point of the fields_to_perturb fields of each ens member
-!         to be randomly perturbed with a standard deviation of perturbation_amplitude.
+!     perturbation_amplitude > 0 allows each point of the fields_to_perturb fields 
+!         of each ensemble member to be randomly perturbed with a standard deviation 
+!         of perturbation_amplitude.
 !         Each field can be given a different perturbation_amplitude.
 !     Used by filter's call to pert_model_copies.
 !
@@ -111,46 +112,67 @@
 ! state_variables (5 columns for each variable):
 !     netcdf varname, dart quantity, min allowed value, max allowed value, (no)update this var
 !
+! vert_normalization_YYY
+!     The vert_normalization_scale_height default value was chosen based on 
+!     Pedatella's settling on 1.5 (scale heights/radian), based on tuning experiments.
+!     This is supported by tuning experiments with CAM5.
+!
 ! use_log_vertical_scale(vertical interpolation only):
 !     .false. or .true.
 !
-! start_damping_ramp_at_pressure
-!     The default values given are the minimums recommended, given the choices
-!     of several other CESM and DART parameters.
-!     You calculate your own as illustrated in models/cam/doc/highest_state_p_Pa.pptx.
-!     Or you can start with the minimum and increase it if there seems to be excessive
+! no_obs_assim_above_level 
+!     Prevents assimilation of observations whose vertical location is above
+!     this model level.  Note that, if this value is set to a large value,
+!     it may be within CAM's hybrid coordinate layers instead of in the pure pressure layers.
+!     This will result in the the observation cutoff height being at different pressure levels
+!     over mountains versus lower areas.
+
+! model_damping_ends_at_level
+!     This controls how much innovations are reduced near the model top, to mitigate the effects 
+!     of the extra diffusion sometimes applied there in CAM and WACCM (see fv_div24del2flag).
+!     The default value (-1) turns off the damping and relies on the choices of the following 
+!     variables to prevent assimilation from happening in CAM's diffusive top layers:
+!        no_obs_assim_above_level,
+!        use_log_vertical_scale,
+!        vert_normalization_YYY,
+!        cutoff.
+!     When it is turned on (> 0), it is the lowest level which will be damped.  
+!     Damping increases with height (smaller level numbers).
+!     The values given below are the minimums recommended for various models.
+!     You can start with the minimum and increase it if there seems to be excessive
 !     noise in the upper layers.
-! The parameters on which the minimum start_damping_ramp_at_pressure depends are:
-!     cutoff (0.2 assumed)
-!     vert_coord
-!     vert_normalization_{pressure,scale_height}
-!     CAM's model top
-!     number of model top levels with extra diffusion
 !
 ! CAM-FV Section
-!     model top 220 Pa
-!     number of model top levels with extra diffusion, controlled by div24del2:
+!     Model top 220 Pa
+!     Number of CAM model top levels with extra diffusion, controlled by div24del2:
 !         2 = div2    -> 2 levels
-!         4,24 = del2 -> 3 levels -> highest_state_pressure_Pa = 10500.
-!     vert_normalization_pressure = 20000. is a better choice than 100000.
-!         for allowing upper levels to be pulled towards the obs.
+!         4,24 = del2 -> 3 levels 
+!     CAM assimilations can use pressure or scale height vertical coordinate.
+!     We recommend scale height.
+!        use_log_vertical_scale          = .true.
+!        vert_normalization_scale_height = 1.5 
+!        vert_normalization_pressure     = 20000. 
+!     
+!     26 levels (CAM4):
+!        no_obs_assim_above_level            = 5       ! corresponds to ~3700 Pa
+!     30 levels (CAM5):
+!        no_obs_assim_above_level            = 5       ! corresponds to ~3800 Pa
+!     32 levels (CAM6):
+!        no_obs_assim_above_level            = 5       ! corresponds to ~3600 Pa
 !
-! WACCM can be used with either FV or SE
-!     vert_normalization_scale_height does not have extensive exploration available.
-!     Pedatella settled on 1.5.
+! WACCM 
 !     The model top for WACCM is (naturally) much higher: 4.5e-4 Pa
-!     This has ramifications for the diffusion near the model top so
-!     changes to start_damping_ramp_at_pressure and no_assim_above_pressure are appropriate.
-!     number of model top levels with extra diffusion, controlled by CAM's fv_div24del2flag:
+!     The number of model top levels with extra diffusion is controlled by WACCM's 
+!     fv_div24del2flag:
 !         2 = div2    -> 3 levels
 !         4,24 = del2 -> 4 levels
+!     70 levels (WACCM4):
+!        no_obs_assim_above_level            = 7       ! corresponds to 0.012 Pa
+!     This values must be used with WACCM assimilations;
+!        use_log_vertical_scale          = .true.
+!     This is recommended, but your own tuning experiments may support a different value.