Sampling Error Table
gen_sampling_err_table
In order to apply Sampling Error Correction, we use gen_sampling_err_table
to compute the statistics described in Anderson (2012). 1
The table with the error correction values is stored in the netCDF file
sampling_error_correction_table.nc
in:
${DARTROOT}/assimilation_code/programs/gen_sampling_err_table/work/
However, the table typically only contains values for ensemble sizes up to 200
ensemble members. Thus we edit input.nml
in the above directory thus we
edit the following namelist to add ensemble sizes of 250, 500 and 1000:
&gen_sampling_error_table_nml
ens_sizes = 250, 500, 1000
debug = .false.
/
We then run quickbuild.csh
and submit.csh
the latter of which simply
submits a batch job that runs gen_sampling_err_table
on a compute node.
The program required 01:53:14 on 8 CPUs to complete and add the correction values for the additional ensemble sizes.
DART_config.template
Finally, we need to edit Line 325 of the DART_config.template
script to
reflect the fact that we are now able to run ensemble sizes of larger than 200.
The template is here:
$ vim ${DARTROOT}/models/cam-fv/shell_scripts/cesm2_1/DART_config.template
And we change 200 to 1000 here:
if ( $num_instances < 3 || $num_instances > 1000 ) then
References
- 1
Anderson, Jeffrey L. (2012) “Localization and Sampling Error Correction in Ensemble Kalman Filter Data Assimilation.” Monthly Weather Review 140: 2359-2371, doi: 10.1175/MWR-D-11-00013.1.