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what is the default timesteps and coupling frequency of CAM6.0, CLM5.0, and POP2



Does anybody know the default timestep of CAM6.0, CLM5.0, and POP2 in a fully coupled simulation (e.g. BHIST_BPRP)? What is the coupling frequency between these three components? How can I check these in an out-of-box case?(Or which variables should I look into in the namelists?) Thank you!


Jesse Nusbaumer
CSEG and Liaisons
Staff member
Hi Eric,

For any particular compset/grid combination you can find the coupling frequency by creating a case and then looking for the "NCPL" variables in env_run.xml. For CAM and CLM, the time step is set by ATM_NCPL, which specifies how many time-steps and coupling events occur for each component over the time period specified by NCPL_BASE_PERIOD.

For POP2, the coupling frequency is given in a similar fashion via OCN_NCPL, but the internal POP2 time-step is specified in the namelist via the dt_option and dt_count variables (which you can find in your case run directory's pop_in file).

In general, I believe CAM/CLM usually has a 30-minute timestep, while POP2 has a 1-hour timestep. However, this can be compset and model-grid dependent. The default coupling frequency (NCPL) for each particular compset/grid combination are specified in CIME here:


where <CESM_SRC_DIR> is wherever your CESM source code is located.

Anyways, I hope that helps, and have a great day!