CESM Guide

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Community Earth System Model (CESM)
Author NCAR
Website http://www2.cesm.ucar.edu/models/cesm1.2/
Source Subversion
Category Modeling, Simulation
Help user guide

From Wikipedia [1]:

The Community Earth System Model (CESM) is a fully coupled numerical simulation of the Earth system consisting of atmospheric, ocean, ice, land surface, carbon cycle, and other components. CESM includes a climate model providing state-of-art simulations of the Earth's past, present, and future. It is the successor of the Community Climate System Model (CCSM), specifically version 4 (CCSMv4), which provided the initial atmospheric component for CESM. Strong ensemble forecasting capabilities, CESM-LE (CESM-Large Ensemble), were developed at the onset to control for error and biases across different model runs (realizations). Simulations from the Earth's surface through the thermosphere are generated utilizing the Whole Atmosphere Community Climate Model (WACCM). CESM1 was released in 2010 with primary development by the Climate and Global Dynamics Division (CGD) of the National Center for Atmospheric Research (NCAR), and significant funding by the National Science Foundation (NSF) and the Department of Energy (DoE).

Setting up CESM

There is no module for CESM because it does not support cluster-wide installation. CESM will try to compile and download files on an as-needed basis. Therefore, you need to perform a few steps to get CESM setup for yourself:

Check for the latest available version using the svn list command:

svn list https://svn-ccsm-models.cgd.ucar.edu/cesm1/release_tags
# Output from the command:

At the time of writing, version highlighted above is the latest. The downloaded files can get quite large, therefore install cesm in the scratch directory:

mkdir -p /scratch/$USER && cd /scratch/$USER
svn checkout --username guestuser --password friendly --non-interactive https://svn-ccsm-models.cgd.ucar.edu/cesm1/release_tags/cesm1_2_2_1

Sometimes the downloads can hang or pause for a long time. Whenever this happens, cancel by holding Control + C keys and rerun the above svn checkout command. In a few minutes, all the files should have downloaded.

Many of the perl commands rely on a CCSMROOT environmental variable, so add that to your ~/.bashrc file, and add the scripts directory to your PATH.

echo -e '\n# CESM settings:' >> ~/.bashrc
echo 'export CCSMROOT=/scratch/$USER/cesm1_2_2_1' >> ~/.bashrc
echo 'export PATH=$PATH:$CCSMROOT/scripts:$CCSMROOT/scripts/ccsm_utils/Tools' >> ~/.bashrc
source ~/.bashrc

The CESM scripts require perl's XML::LibXML module, so load a recent perl module which has that installed:

module initadd perl/5.14.4
module load perl/5.14.4

Now test the create_newcase script:

create_newcase -list

If all is well, you should see a usage message instead of a perl warning.