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The NCAR Community Climate Model (CCM3)We have found a problem in ccm3.2 on the NCAR CRAY computers due to changes made in the f90 compiler over the last several months. We did check CCM extensively when we moved from cf77 to f90. However, the f90 compiler is periodically updated with "minor" patches and we are not informed about these modifications. We do not know when this problem first appeared, however, it was after March 1997.
The compiler incorrectly deals with a vector loop within the lsm code resulting in an incorrect calculation. The symptom is that energy is no longer conserved within the lsm. This effect is not normally evident since energy and mass conservation is not checked within the lsm by default. The lsm namelist variable, conchk, must be set to true for energy and mass conservation to be verified.
If a user wants to determine if a run performed on the NCAR CRAY computers had this problem, the user should repeat the first several days of the original run with the original code. If the difference between the two results is within the rounding error growth (see Rosinski and Williamson, SIAM J. Sci. Comput, Vol18., No.2, pp552-564, March 1997) then the compiler error existed in the original run.
To apply the patch move to your "ccm3" directory and if patch is installed you can do the following...
patch < ccm3_2_fix_patch
This is the same as the distribution on the CCM3 source-code download page.
(HINT: Use the commands "gunzip" and "tar -xvf" to unzip and/or untar these files.)