Merge pull request #400 from NCAR/improved_roms_model_mod

Add pert_model_copies subroutine to ROMS model_mod

CHANGELOG.rst

@@ -22,6 +22,13 @@ individual files.
 
 The changes are now listed with the most recent at the top.
 
+**September 21 2022 :: ROMS model_mod perturbation routine Tag: v10.4.0**
+
+- Adds a pert_model_copies subroutine to the ROMS model_mod to enable proper 
+  functioning of perturb_single_instance for ROMS.
+- Updates ROMS documentation with an explanation of how to generate an initial
+  ensemble of history files.
+
 **September 16 2022 :: Bug-fix for CLM shell scripts. Tag: v10.3.2**
 
 - Fixes dtlimit bug in cesm2.2 CLM shell scripts.  Loads all CAM

conf.py

@@ -17,11 +17,11 @@
 # -- Project information -----------------------------------------------------
 
 project = 'DART'
-copyright = '2021, University Corporation for Atmospheric Research'
+copyright = '2022, University Corporation for Atmospheric Research'
 author = 'Data Assimilation Research Section'
 
 # The full version, including alpha/beta/rc tags
-release = '10.3.2'
+release = '10.4.0'
 master_doc = 'README'
 
 # -- General configuration ---------------------------------------------------

models/ROMS/model_mod.f90

@@ -86,8 +86,8 @@ module model_mod
 use location_io_mod,      only :  nc_write_location_atts, nc_get_location_varids, &
                                   nc_write_location
 
-use default_model_mod,     only : pert_model_copies, nc_write_model_vars, init_conditions, &
-                                  init_time, adv_1step
+use default_model_mod,     only : nc_write_model_vars, init_conditions, init_time, &
+                                  adv_1step
 
 use typesizes
 use netcdf
@@ -674,6 +674,45 @@ subroutine nc_write_model_atts(ncid, domain_id)
 
 end subroutine nc_write_model_atts
 
+
+subroutine pert_model_copies(state_ens_handle, ens_size, perturbation_amplitude, interf_provided)
+
+type(ensemble_type), intent(inout) :: state_ens_handle
+integer,             intent(in)    :: ens_size
+real(r8),            intent(in)    :: perturbation_amplitude
+logical,             intent(out)   :: interf_provided
+
+integer     :: var_type
+integer     :: j,i 
+integer(i8) :: dart_index
+type(location_type) :: location
+
+! Storage for a random sequence for perturbing a single initial state
+type(random_seq_type) :: random_seq
+
+if ( .not. module_initialized ) call static_init_model
+
+interf_provided = .true.
+
+! Initialize random number sequence
+call init_random_seq(random_seq, my_task_id())
+
+! Perturb the salinity and temperature fields
+
+do i=1,state_ens_handle%my_num_vars
+   dart_index = state_ens_handle%my_vars(i)
+   call get_state_meta_data(dart_index, location, var_type)
+   if (var_type == QTY_TEMPERATURE .or. var_type == QTY_SALINITY) then
+      do j=1, ens_size
+         state_ens_handle%copies(j,i) = random_gaussian(random_seq, &
+            state_ens_handle%copies(j,i), &
+            perturbation_amplitude)
+      enddo
+   endif
+enddo
+
+end subroutine pert_model_copies
+
 !-----------------------------------------------------------------------
 !> writes the time of the current state and (optionally) the time
 !> to be conveyed to ROMS to dictate the length of the forecast.

models/ROMS/readme.rst

@@ -49,7 +49,18 @@ The DART forward operators require interpolation from the ROMS terrain-following
 and horizontally curvilinear orthogonal coordinates to the observation location.
 Please contact us for more information about this interpolation.
 
-A Note About Filenames
+Generating an initial ensemble
+------------------------------
+
+The ROMS interface provides the ability to create an ensemble of initial ROMS
+history files from an initial file by using the
+:doc:`/assimilation_code/programs/perturb_single_instance/perturb_single_instance`.
+You can specify an ensemble of any size in the ``perturb_single_instance``
+namelist in ``input.nml`` and this program will randomly perturb the 
+temperature and salinity fields of an initial ROMS history file to generate 
+the ensemble.
+
+A note about filenames
 ----------------------
 
 During the course of an experiment, many files are created. To make them unique,