When running in cam mode, certain CLM2.1 namelist variables cannot be set independently. In particular, any user specification for the namelist variables, CASEID, CTITLE, IRAD, NSREST, HIST_CRTINIC, HIST_NHTFRQ(1), HIST_MFILT(1) and MSS_IRT will be overwritten by values obtained from CAM2 at startup. All other namelist settings may be set independently by the user.
The following table specifies the namelist variables that are overwritten with values obtained from cam and lists the associated CAM2 namelist variable and its default value.
| CLM Namelist | CAM namelist | CAM default |
| CASEID | CASEID | required |
| CTITLE | CTITLE | blank |
| NSREST | NSREST | 0 |
| IRAD | IRADSW | -1 |
| HIST_CRTINIC | INITHIST | 'MONTHLY' |
| HIST_NHTFRQ(1) | NHTFRQ(1) | 0 |
| HIST_MFILT(1) | MFILT(1) | 1 |
| MSS_IRT | MSS_IRT | 365 |
The minimum set of model input namelist variables that must be given values by the user at run time depends on if a pre-existing surface dataset already exists and if RTM river routing is enabled. At a minimum, only the namelist variables FPFTCON and FSURDAT must be given values if a model surface dataset exists and if the cpp variable RTM is not defined. If a monthly surface dataset does not exist, then MKSRF_FVEGTYP, MKSRF_FSOITEX, MKSRF_FSOICOL, MKSRF_FLANWAT, MKSRF_FGLACIER, MKSRF_FURBAN, and MKSRF_FLAI must be given values in order to generate one at runtime. If RTM is invoked, then FRIVINP_RTM must also be specified. Finally, the namelist variable FINIDAT must be set if a pre-existing initial dataset is to be utilized.