Welcome to CCSM

expand   collapse


CCSM Research Tools: May 17 2002 CAM2.0 Model Release

Model Release

The Community Atmosphere Model version 2.0 (CAM2.0) was released along with CCSM2.0 on Friday May 17, 2002. CAM2.0 is the latest in the development of the CCSM atmosphere model and was renamed from Community Climate Model (CCM). This version of the model includes updates to both the science and software engineering of the model. The CAM2.0 Users Guide goes through all the updates from CCM3.6.6 to CAM2.0, but the major science changes include:

  • Incorporated P.J. Rasch and J.E. Kristjansson (1997) prognostic cloud-water parameterization.
  • Incorporated W. Collins (2001) scheme to to allow a greater variety of cloud overlap assumptions. The default cloud overlap assumptions are for maximum overlap when clouds exist in two adjacent layers, and random overlap when there is a gap between clouds.
  • Updated water vapor absorptivity and emissivity with the work of Hackney, and Edward (2002).
  • Ice-model changed to use the CCSM Community Sea-Ice Model (CSIM), and land-model changed to use the Community Land Model (CLM).
  • Model operates on fractional land, ocean and sea-ice area's rather than area's defined by only one surface type.
  • Parameterization of precipitation evaporation was added to the model.
  • New datasets with 26 instead of 18 levels, and a new updated Ozone dataset.

Changes to the software engineering of the model include:

  • Model history output now directly in NetCDF format.
  • 2D parallel decomposition for the physics.
  • More clear seperation of physics and dynamics.
  • Changes to namelist options.
  • Development of new build scripts.

This version of the model is considered a "pre-release" of the model that will be done shortly before the CCSM workshop. The new release will include support on Solaris and the Compaq-alpha cluster. It will also include support for reduced-grid operation, interpolation tools, and will have more complete testing on all namelist options. Because, this version will be more robust and stable we recommend that users that can wait a month do so in order to get a better version of the model to work with.

Erik Kluzek, CCSM Software Engineering Group, email: erik@ucar.edu