PRECIS

PRECIS user support page

This page is intended to provide users with hints and tips on setting up and running PRECIS experiments.

We welcome user input to help us develop the model and expand our FAQs.  Please e-mail us at precis@metoffice.gov.uk.

Two useful sources:

PRECIS handbook (PDF format, 1.8MB)
    Discusses scientific questions relevant to setting up experiments and using PRECIS output

PRECIS Technical manual (PDF format: 2.3MB).
    Installing and running PRECIS; also includes some advice on experimental design.

Links to other sources of information:

David Hassell's notes on using the model output

Installation of PRECIS:

Notes on the Installation of PRECIS

          Precis installs correctly, but when I try to start an experiment, nothing happens.

           Most likely you haven't activated the at daemon, which PRECIS needs in order to function.  To activate the at daemon, go into your linux distro's control panel (control center / yast / etc) and look for something that says runlevel editor.   "  at  " should be somewhere in that list.  Activate or check it.  It should begin running immediately, and your PRECIS job should now start.  

          Unable to locate dump file / pp4lbc file

              This error occurs when PRECIS looks at the setvars file ( ~/setvars ) to determine where to read in boundary data and start dump files and does not find the expected file.  This can happend if 1) $PP4LBCDIR and $DUMPSDIR point to a location other than where the data actually is or 2) $PP4LBCDIR and $DUMPSDIR are corrected but the boundary data present is zipped.  Make sure that those two variables point to the correct location on your disk where the files live, and make sure that all the data is unzipped.  NOTE that PRECIS expects all dump files in one directory $DUMPSDIR, but expects boundary data in subdirectories of $PP4LBCDIR based on the runid of the boundary data (i.e. $PP4LBCDIR/addfa , $PP4LBCDIR/adqcm ).  The Runids are listed in the PRECIS user interface window where you choose the scenario.  See more information at this weblink which explains how to install boundary data received on hard drive.

          PRECIS stops due to the disk filling up

             PRECIS produces a large quantity of output data, especially if you have chosen to output hourly means.  We have seen many cases where users have filled up their hard drives with output data.  Once PRECIS cannot output to disk, it ceases running with an error.  The solution to this is to output the data to a separate partition (preferably with lots of space) from the install partition.  Remember to update $ARCHIVEDIR in ~/setvars to reflect the change.  Another solution is to periodically delete data from $ARCHIVEDIR for stash codes you do not need.  You can do this even while PRECIS is running.  You can automate this deletion using a cron job or the at daemon.

          Region not Spanned

             When a user receives boundary data from the Hadley Centre to run PRECIS, the boundary data is never global but instead represents just a region of the world pertinent to their need.  When the user selects a region from the user interface, if he or she attempts to set up a region outside of the region of the global boundary data, PRECIS will give an error.  The solution is to redraw your selected region smaller.

          GrADS / CDAT issues

             In ~/analysis_tools/grads are three files: grads_map.gs  /  grads_map.txt  /  plot_example.gs  .  Grads_map.gs is a script you can run in GrADS that corrects the rotation of the map due to PRECIS's rotated coordinate system.   Note that as a rule technical support for using GrADS and CDAT are not provided.   We recommend that you make use of the analysis tools installed with PRECIS that work on output pp files - you can always convert from pp to netcdf or pp to grib later on using conversion tools in ~/um/bin (pp2ctl and ppnc).

Once the PRECIS user has run tests with the sample data included on the installation DVD and is ready to proceed further, he or she may request lateral boundary conditions files that will be used to drive PRECIS.  More information is in the "Obtaining Data" section here.

Please send an email to precis@metoffice.gov.uk requesting the boundary data.  Please include

Which experiments you would like data for (i.e. ERA40, control, A2)

Whether you require sulphur prognostic boundary data for the HadAM3P experiments

Latitude and Longitude values for your chosen region (N,S,E,W)

The data will be extracted from the global data archives and written to an IDE hard drive to be sent to you.  Once you receive the hard drive, please consult the tutorial on installing the hard drive and boundary data.