active or prognostic component

Solves a complex set of equations to describe a sub-model’s behavior.

case (CASE)

An instance of a global climate model simulation. A case is defined by a component set, a model grid, a machine, a compiler, and any other additional customizations.


A sub-model coupled with other components to constitute a global climate modeling system. Example components: atmosphere, ocean, land, etc.

component set (COMPSET)

A complete set of components to be linked together into a climate model to run a specific case.

data component

Replacement for an active component. Sends and receives the same variables to and from other models (but ignores the variables received).

grid (GRID)

A set of numerical grids of a case. Each active component operates on its own numerical grid.


Used to refer to a set of grids. Each grid within a set may have different resolution.

stub component

Simply occupies the required place in the climate execution sequence and does send or receive any data.



A component of the CIME infrastructure that is run from within the driver. It can be run on a subset of the total processors, and carries out mapping (interpolation), merging, diagnostics, and other calculations.


The hub that connects all components. CIME driver runs on all hardware processors, runs the top level instructions, and, executes the driver time loop.


An imposed perturbation of Earth’s energy balance

Model Coupling Toolkit or MCT

A library used by CIME for all data rearranging and mapping (interpolation)


Determines land/ocean boundaries in the model


Interpolation of fields between components.

Files and Directories

archive directory (DOUT_S_ROOT)

If short term archiving is activated (DOUT_S = TRUE), the restart files and run output files are copied to archive directory location (DOUT_S_ROOT).

build directory (EXEROOT)

Location where the case is built.

case root (CASEROOT)

The directory where the case is created. Includes namelist files, xml files, and scripts to setup, build, and run the case. Also, includes logs and timing output files.


The directory where the CIME source code resides

history files

NetCDF files that contain fields associated with the state of the model at a given time slice.

initial files

Files required to start a file

input data stream (DIN_LOC_ROOT)

A time-series of input data files where all the fields in the stream are located in the same data file and all share the same spatial and temporal coordinates.

namelist files

Each namelist file includes input parameters for a specific component.

run directory (RUNDIR)

Where the case is run.

restart files

Written and read by each component in the RUNDIR to stop and subsequently restart in a bit-for-bit fashion.

rpointer files

Text file written by the coupler in the RUNDIR with a list of necessary files required for model restart.

XML files

Elements and attributes in these files configure a case. (building, running, batch, etc.) These files include env_archive.xml, env_batch.xml, env_build.xml, env_case.xml, env_mach_pes.xml, env_mach_specific.xml, env_run.xml in CASEROOT and can be queried and modifed using the xmlquery and xmlchange tools.


sandbox (SRCROOT)

A checked out tag on a local or a remote machine. may be edited to create a new tag. or, may just be used for running cases.

source modifications (CASEROOT/SourceMods)

one or more source files that are modified by the user. Before building a case, CIME replaces the original source files with these files.


A snapshot of the source code. With each consecutive tag (one or more) answer-changing modifications to the source code of a component are introduced.

user namelist files (CASEROOT/user_nl_*)

User modifications for a given case can be specified in these files.



A set of test cases that is run using a tag which is complete, tested, and has no modifications in the source code. Used to assess the performance/accuracy of a case that is run using a sandbox.

baseline failure

A test that fails in its comparison with a baseline.


Part of the unit testing framework used by CIME scripts regression tests.

regression test

A test that compares with baseline results to determine if any new errors have been introduced into the code base.

unit testing

A fast, self-verifying test of a small piece of code.



External System Processing: handles data assimilation