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Each participant will have a training user account on the ECMWF Cray system. This is different from the user account on the classroom computers.
Begin by logging onto the Cray login nodes:
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ssh trcrayXX@ccb <<< use your Cray user id Password: xxxxxxxx trcray@ccb-login2:~> |
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An ensemble experiment consists of a 'control' and multiple 'perturbed' forecasts, or 'ensemble members'. For the operational ECMWF ensemble forecast, 50 members are used.
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The exercises show how to create the experiment directories, prepare the jobs and submit them to the ECMWF Cray.
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Please only use the 2013102400 start date to ensure we can create the single full ensemble from everyone's runs in the class. Use the createENS command to create an ensemble with just a single member. |
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Change to the experiment directory labelled by the date chosen:
There are two experiment directories: cf000 and pf001. cf000 is for the control forecast which is not used here. pf001 is the single perturbation forecast.
Understand what the different files in the experiment directory are for. ICM* : these are the initial starting files. ICMGG* are the initial gridpoint files, ICMSH* are the initial spectral fields. Use the 'grib_ls' command to examine the initial files:
The file: namelistfc is the model 'NAMELIST'. It contains a list of variable settings or 'switches' that control what the model does. These variables are grouped into separate fortran namelists. |
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Make a copy of the namelist file and edit it to set the ensemble member value to the one you are given. Make sure you are in the 'pf001' directory.
and make the following changes to the namelist variables:
The variable NENSFNB is important as this determines the random number seed used by the stochastic schemes, by altering the ensemble member value.
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This is different from how the ensemble would be run in practisepractice. Ensemble member '2' would be run in directory pf002, member number '3' in pf003 and so on. But to keep this exercise simple, everyone will use the same experiment directory name but with a different ensemble member number. |
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Create and submit Cray batch job
The next steps are to create and submit a batch job to run on the ECMWF Cray XC30 system.
To create the batch job, use the oifs_run command. This creates a small batch job file ready to submit.
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Use the The command will create a create a file ' Submit this job:
Check the job status:
These forecasts complete in about 15mins. |
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Using your favourite text editor, check this file to make sure the model has run correctly. It's usually best to start from the bottom of the file and scroll up. If you see:
the model has failed. |
The output from each model run goes into a directory named according to this run number. e.g. the default is 'output1'. So job2 would write the output to 'output2' and so on.
If the model fails, there are 2 files to look at in the appropriate 'output' directory:
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