Task SetEns

The task SetEns runs automatically and foremost whenever ensemble runs are performed. It generates and sets the ensemble members by perturbing a reference state which defines so-called central or reference member. This task also creates a structure of sub-folders (0001, 0002, etc...) where the input and output files for each ensemble member are stored. In order to enable ensemble runs, FALL3D must be executed with the argument -nens, which defines the ensemble size. The parameters to be perturbed are defined in the block ENSEMBLE of the configuration file. In addition, in this block it's possible to set the perturbation amplitude (given as a percentage of the reference value or in absolute terms) and the perturbation sampling strategy (constant or Gaussian distribution).

Notes:

  • The ENSEMBLE block in the configuration file is ignored when the ensemble option is disabled
  • This task is available since the code version 8.1.

Input file

This task requires the namelist file name.inp and the random number files name.ens under the ensemble member sub-folders contain the random numbers required to construct the ensemble. They must be read whenever an ensemble run is performed and the variable RANDOM_NUMBERS_FROM_FILE is set to YES in the configuration file.

Output files

LOG file

The LOG file name.SetEns.log is an ASCII file where the status of the task is reported. In addition, the random numbers used to construct the ensemble are summarized here.

Random number files

The random number files name.ens under the ensemble member sub-folders contain the random numbers required to construct the ensemble. The random numbers are regenerated and the files name.ens updated in every new run as long as the variable RANDOM_NUMBERS_FROM_FILE is set to NO in the configuration file. Otherwise, the files name.ens are read in a new ensemble run and remain unchanged. This is useful to reproduce a previous ensemble run, for example. If the files name.ens do not exist (e.g. in a first run), they are generated regardless of the value assigned to RANDOM_NUMBERS_FROM_FILE.