CSM Flux Coupler (CPL)

CSM software is based on a framework which divides the complete climate system into component models connected by a flux coupler. This design requires four component models -- atmosphere, land, ocean, and sea-ice -- each connected to the coupler, and each exchanging data with the coupler only. From a software engineering point of view, the CSM is not a particular climate model, but a framework for building and testing various climate models for various applications. In this sense, more than any particular component model, the flux coupler defines the high-level design of CSM software.

The flux coupler code has several key functions within the CSM framework:

  • It allows the CSM to be broken down into separate components, atmosphere, sea-ice, land, and ocean, that are "plugged into" the flux coupler. Each component model is a separate code that is free to choose it's own spatial resolution and time step. Individual components can be created, modified, or replaced without necessitating code changes in other components. CSM components run as separate executables, communicate via message passing (MPI in particular), and can be distributed among several computers.
  • It controls the execution and time evolution of the complete CSM by controlling the exchange of information between the various components.
  • It computes interfacial fluxes between the various component models (based on state variables) and distributes these fluxes to all component models while insuring the conservation of fluxed quantities.


Following are several versions of the CSM flux coupler software. Note that the Coupler code merely connects atmosphere, sea-ice, land, and ocean component models -- the component models themselves must be supplied separately.

  • Version 7.0

    This release coincided with the release of complete coupled system, CCSM4.0
  • Version 6.0 (released 23 June 2004)

    This release coincided with the release of complete coupled system, CCSM3.0
  • Version 5.0 (released 17 May 2002)

    This release coincided with the release of complete coupled system, CCSM2.0
  • Version 4.0 (released 31 July 1998)

    A beta version of this version of the code was used for a lower-resolution 130 year fully coupled experiment that was presented at the June 1997 CSM Workshop. Perhaps the most notable distinction between this code and versions 3.n is that is that the Coupler treats all components models, sea-ice, ocean, atmosphere, and land, as four separate entities. Other improvements include enhanced diagnostics and portability.

    • Documentation -- NCAR Technical Note, June 1997.

      This documents a beta version of the 4.0 release.
    • User's Guide -- html User's Guide, August 1998.

      This is an updated version of the User's Guide contained in the June 1997 Technical Note.
    • Source Code (download)
  • Version 3.a.2 (released 18 Sept 1996)

    This version of the code was used for a 300 year fully coupled run and a companion run with increasing CO2 during the fall and winter of 1996/1997. These runs were presented at the June 1997 CSM Workshop (also see the 16 May 97 issue of Science). This version varies only slightly from version 3.a. This code is made available largely to document the code was used for certain major coupled climate simulations.

  • Version 3.a (released 6 June 1996)

    This is the first release of the Coupler code and is essentially the same as that used for the fully coupled experiment presented at the May 1996 CSM Workshop. In this version, the land model is embedded within the atmosphere model, thus the coupler does not treat the atmosphere and land models as separate entities.


The NCAR CSM Flux Coupler is subject to Copyright (C) 1996, 1997, 1998, 1999, 2000, University Corporation for Atmospheric Research, All Rights Reserved.