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The NCAR Community Climate Model (CCM3)CCM Users;
A version of CCM3.6.6 which runs efficiently on clustered architectures such as the IBM SP3 and Compaq ES40 cluster is now available. At T42 the code can utilize up to 64 processors, though scaling is reasonably good only up to 32. On a clustered machine, the number of nodes on which the code is run must divide evenly into the number of model latitudes.
When run on any of NCAR's SGI Origin machines, the simulation is identical to that produced with the old CCM3.6.6 tar file provided f90 is used to build both models. The solution produced has been verified correct to roundoff error on NCAR's SP3, ES40 cluster, as well as a Linux PC and Sun workstation. For the moment this code is not configured to run through the CSM flux-coupler.
Some differences exist in the boundary datasets provided with this distribution as compared with CCM3.6.6. First, the land model initial dataset had to be modified because dimension names in the metadata changed. Thus the LSM initial dataset provided with the CCM3.6.6 distribution will not work with the new code. Second, a more modern ozone dataset is provided (noaao3.1990.21999.nc), though the old one from CCM3.6.6 (ozn.0596.r8.nc) will still work. Boundary datasets suitable for running the code are included in the source code tar file. So there is no need to retrieve a separate tar file of datasets.
To get the new tar file, type:
ftp ftp.ucar.edu
login:
or get it from the following link:
ftp://ftp.ucar.edu/ccm/ccm3.10.11.brnchT.366physics.4.tar.gz
For those interested, the rough meaning of the above long name is "CVS tag 4 from an in-house development code (CCM3.10.11) which was modified to be replaced with CCM3.6.6 physics".
The model now writes its history information directly in netcdf format, rather than fortran binary as before. It turned out that incorporating this modification from the in-house development code was critical to achieving reasonable performance on clustered machines. Since namelist specification for history tape quantities changed with the new history handling mechanism, most old namelists based on CCM3.6.6 will not work with the new code. The land model (LSM) namelist also changed slightly. See the README included in the tar file for details of the changes.
Users familiar with CCM3.6.6 code will find that that the new code has changed substantially. The primary reasons for this are 1) we are migrating to Fortran 90, and 2) the message-passing implementation of the model was totally rewritten. One consequence of the Fortran 90 migration is that some files in the distribution end in .F (fixed form), and others end in .F90 (free form). Eventually all source files will be free-form.
Feel free to contact me directly about any problems encountered in building or running this code.
Alse see... Averaging flags for CCM3.10.11 with CCM3.6.6 physics branch code for a note about another feature of this code.
Jim Rosinski CCM Core Group rosinski@ucar.edu