6 Running the Data Model

6.1 Overview

The datm cannot run by itself, it can only execute in the context of running the complete CCSM system - a framework that requires atmosphere, ice, land, and ocean components, as well as a coupler component. The scripts that build and run the CCSM system are described in detail in the CCSM User's Guide, a holistic guide to running the complete system. This Guide includes a line-by-line explanation of the master run script and data model "setup scripts". A brief description of the CCSM run scripts is below. See the CCSM User's Guide for complete information.

6.2 Master Run Script and Component Setup Scripts

Two levels of c-shell scripts are used to build and run the CCSM system. A master "run script" coordinates the building and running the complete system while the component model "setup scripts" are responsible for configuring each individual CCSM component (including datm). Each CCSM component setup script is run in its own, separate subdirectory, where its executable resides and in which all of its input and output files are kept. The CCSM execution is controlled by the master script, referred to as "the run script".

The run script has the following tasks:

a.

Set batch system options

b.

Define common build and run environment variables

c.

Select multi-processing and resolution specs

d.

Run the setup script for each component

e.

Run the CCSM Integration.

f.

Archive/harvest/resubmit when this run is finished

The common build and run environment variable defined in the run script are automatically propagated to each of the component model setup scripts. These variables define such things as the machine architecture, the number of CPUs to run on, common experiment and file naming conventions.

Once the master run script has defined the common environment, each of the component models (cpl, atm, ice, lnd, and ocn) are configured using individual component setup scripts (e.g. datm.setup.csh) which:

a.

Parse the environment variables sent from the master run script. These are, in effect, input variables that might be required by a setup script or otherwise might alter the behavior of the setup script.

b.

Position or create any input data files, as necessary, including input namelist data files and climatological data files.

c.

Build the component model executable.

Finally, when all of the component model setup scripts have successfully completed, the run script executes all CCSM components simultaneously. The CCSM component models run simultaneously as a multi-program/multi-data (MPMD) message passing system, using MPI to exchange data.