The NCAR Community Climate Model (CCM3)

CCM3 Simulation Datasets.

I. Introduction

This page documents the CCM3 simulations run at NCAR.

CCM3: The algorithms defining the NCAR Community Climate Model, Version 3 (CCM3) were frozen and released for general use in May 1996. The algorithms defining CCM3 are detailed in NCAR TN-420 "Description of the NCAR Community Climate Model (CCM3)" (Kiehl et. al. 1996). That technical note also provides a complete list of references to papers that provide the developmental background for many of the components in CCM3. NCAR TN-421 "User's Guide to NCAR CCM3" (Acker et. al. 1996), provides technical details of the model and history files, for the first runs with CCM3.0. The latest code (CCM3.6) is documented in CCM3.6 User's Guide. The CCM3 code itself is documented with inline comments. The final version of the model, as documented in NCAR TN-420 and NCAR TN-421, is referred to as CCM3.0. The latest public release of the model is CCM3.6.6.

The first simulations were carried out with earlier versions of the code, referred to here as Prototype-CCM3 and Beta-CCM3, the latest simulations were with CCM3.3.31 (similar climate to CCM3.6) and CCM3.5.27 (bit-for-bit with CCM3.6):

Prototype-CCM3 is a preliminary version of CCM3. This version is NOT bit-for-bit equivalent to CCM3, but the differences should not produce a significantly different climate than that of CCM3. The modifications to Prototype-CCM3 to make CCM3, which affect the simulations, are: 1. upward longwave radiation for the sea-ice (sigma*Ts**4) was changed to use time level (n) rather than time level (n-1), 2. evaporation of large scale stable rain was modified to reduce creation of supersaturated layers (a rare event) and 3. the surface type datasets have a few points on the Ross ice shelf changed from sea ice to glacier. Output history tapes from this version used the standard CCM2 MSS pathname convention: /USERNAME/ccm2/CASE/hist or /USERNAME/ccm3/CASE/hist (where USERNAME is the user's name and CASE is the case name of the simulation).

Beta-CCM3 is a second preliminary version of CCM3, but bit-for-bit equivalent to CCM3. Any code differences between Beta-CCM3 and final CCM3 are the result of code-cleanup and documentation. Output history tapes from this version used the standard CCM2 MSS pathname convention with "ccm2" replaced by ccm3": /USERNAME/ccm3/CASE/hist (where USERNAME is the user's name and CASE is the case name of the simulation).

CCM3.3.31 is a pre-released development version of CCM3.6. This version did not have the bug-fixes that were added into CCM3.6 ( http://www.cgd.ucar.edu:80/cms/ccm3/news/bug_fixes_in_ccm3.6.shtml). There were also a lot of code advances that were not yet implemented. The only advance that effects simulation greater than roundoff was that capping was not yet applied to snow over land-ice. Output history tapes from this version used the standard CSM MSS pathname convention /USERNAME/csm/ccm3/CASE/hist (where USERNAME is the user's name and CASE is the case name of the simulation).

CCM3.5.27 is a pre-released development version of CCM3.6. This code was tested bit-for-bit with the publically released CCM3.6. Any code differences between CCM3.5.27 and CCM3.6 are the result of code-cleanup and documentation. Output history tapes from this version used the standard CSM MSS pathname convention /USERNAME/csm/ccm3/CASE/hist (where USERNAME is the user's name and CASE is the case name of the simulation).

The history tapes from the various simulations are available for community use. In addition, various condensations of the original history tapes are also available. These simulations and condensations represent a large investment of computing resources and provide a valuable data base for further analysis by the diverse group of CCM researchers interested in a wide variety of problems. All these simulations are available for open, general use.

(Note: The following CCM3 datasets are archived on the NCAR SCD Mass Storage System (MSS). To access them, a NCAR Login is needed.