Login to ECMWF Cray

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:

ssh trcrayXX@ccb                        <<< use your Cray user id
Password: xxxxxxxx

trcray@ccb-login2:~>

The contents of the account should look like:

trcray1@ccb-login2:~> ls
bin  modules.sh  oifs38r1  scratch

If any are missing please let us know.

Directory: oifs38r1

This directory contains the OpenIFS source code and OpenIFS executable.

For the purpose of this workshop, the model has already been compiled to avoid delay and adding unnecessary load to the login nodes.

Examine the files in the oifs38r1 directory.

Directory: scratch

This is the directory in which we will run OpenIFS.

Setting the correct environment

Each time you login and before doing any work in this account, make sure you have the correct environment loaded to run and work with OpenIFS.

source bin/modules.sh

This will load the appropriate modules for OpenIFS and set the choice of compiler and build environment. It is good practise to use something similar for your own OpenIFS installation.

Creating the OpenIFS ensemble experiment

An ensemble experiment consists of a 'control' and multiple 'perturbed' forecasts, or 'ensemble members'. For the operational ECMWF ensemble forecast, 50 members are used.

For this exercise, to save computer time, each participant will run a single, different 'ensemble member' and we will create the complete forecast ensemble from the individual ensembles run by the class as a whole. A later exercise will show how to do this from the model output GRIB files.

The first exercises show how to create the experiment directories, prepare the jobs and submit them to the ECMWF Cray.

createENS command

Use the command createENS to create the ensemble experiment:

createENS --help

usage: createENS [-h] -d <startdate/enddate/hr_inc> [-m <members>]
Set up ensemble forecast for the OpenIFS 2015 workshop
optional arguments:
  -h, --help            show this help message and exit
  -d <startdate/enddate/hr_inc>, --date <startdate/enddate/hr_inc>
                        List of date(s) to retrieve, format: YYYYMMDDHH. The
                        only dates available are: 2013102400/2013102700/24
  -m <members>, --members <members>
                        Number of ensemble members to create e.g. 3 (default 1)

Decide which of the available dates to use. Use the createENS command to create an ensemble with just a single member.

Change to the experiment directory labelled by the date chosen:

cd scratch/ENFO/2013102400/       #  your date may be different

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.

cd pf001
ls

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:

grib_ls ICMGGgc1dINIT
grib_ls ICMSHgc1dINIT

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.

Creating the OpenIFS namelist

Set the ensemble member

In IFS, each ensemble member uses the stochastic physics schemes to generate uncertainty. A random number 'seed' is used by the stochastic scheme to generate a different forecast. This random number seed is changed by altering the ensemble member value in the model's namelist. Each ensemble member must have a unique number and therefore random number seed, in order to produce a different forecast.

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.

cp namelistfc mynamelist

vi mynamelist        # or use your favourite text editor; emacs etc.

and make the following changes to the namelist variables:

CTYPE="pf",   ! change the type of forecast to perturbed

NENSFNB=2,    ! change the ensemble member number to your assigned value. 

LSTOPH_SPBS=true,  ! this enables the stochastic backscatter scheme in the model dynamics

LSPSDT=true,       ! this enables the stochastic scheme for the physics tendencies

The variable NENSFNB is important as this determines the random number seed by altering the ensemble member value.

diff mynamelist namelistfc

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.

oifs_run -e exptid [-m path-to-master.exe] [-r resolution] [-l namelist] [-s timestep] [-n nproc] [-f fcast len] [-x run number] [-q]

 Use the oifs_run command to create the job. You need to give a value to the '-e' and '-l' options. The '-l' option is the name of the namelist file you edited above.

The command will create a create a file 'job1'.

Submit this job:

qsub job1

Check the job status:

qstatu

 

Checking job status: qstatu