Jump to DART Documentation Main Index
Utility program which computes a table of values needed to apply Sampling Error Correction (SEC) during assimilation. These values are used to correct covariances based on small sample size statistics. See reference below.
The name of the SEC table is always sampling_error_correction_table.nc. This is a NetCDF format file. If this file already exists in the current directory any tables for new ensemble sizes will be appended to the existing file. If the file does not exist a new file will be created by this tool. The resulting file should be copied into the current working directory when filter is run.
A file with 40 common ensemble sizes is distributed with the system. Any new ensemble sizes can be generated on demand. Be aware that the computation can be time consuming. The job may need to be submitted to a batch system if many new ensemble sizes are being generated, or start the job on a laptop and leave it to run overnight.
The file contains a "sparse array" of ensemble sizes. Only sizes which have an existing table are stored in the file so large ensemble sizes do not require a large jump in the size of the output file.
This program uses the random number generator to compute the correction factors. The generator is seeded with the ensemble size so repeated runs of the program will generate the same values for the tables.
This namelist is read from the file input.nml. Namelists start with an ampersand '&' and terminate with a slash '/'. Character strings that contain a '/' must be enclosed in quotes to prevent them from prematurely terminating the namelist.
&gen_sampling_error_table_nml ens_sizes = -1 debug = .false. /
|ens_sizes||integer(200)||List of ensemble sizes to compute Sampling Error Correction
tables for. These do not need to be in any particular order. Duplicates
will be removed and any sizes which already have tables computed in the
output file will be skipped. The file which comes with the system
already has tables computed for these ensemble sizes:
ens_sizes = 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 18, 20, 22, 24, 28, 30, 32, 36, 40, 44, 48, 49, 50, 52, 56, 60, 64, 70, 72, 80, 84, 88, 90, 96, 100, 120, 140, 160, 180, 200
|debug||logical||If true print out debugging info.|
To add tables for ensemble sizes 128 and 256 run the program with this namelist:
&gen_sampling_error_table_nml ens_sizes = 128, 256, debug = .false. /
types_mod utilities_mod random_seq_mod netcdf
This table was regenerated using a different random number generator than the Lanai release of DART used. If you are doing a regression test with Lanai and have Sampling Error Correction enabled you will not get bitwise reproducible results. Contact the DART team if you are interested in a table that includes the exact tables used in the Lanai version.
|Contact:||DART core group|
|Revision:||$Revision: 11403 $|
|Source:||$URL: https://svn-dares-dart.cgd.ucar.edu/DART/releases/Manhattan/assimilation_code/programs/gen_sampling_err_table/gen_sampling_err_table.html $|
|Change Date:||$Date: 2017-03-27 17:26:22 -0600 (Mon, 27 Mar 2017) $|
|Change history:||try "svn log" or "svn diff"|