The need to SPIN UP for branch runs

[atmospherics]

I have a question about whether there's a need to spin up for branch runs. Specifically, I am using a restart file dated 1955-01-01, but the STARTDATE is defaulted to 1979-01-01 and cannot be changed due to the branch run's constraints. Can I assume that performing a branch run from a preset STARTDATE (1979-01-01) far ahead from the restart file's REFDATE (e.g., 1955-01-01) means that the model has already been spun up to a stable state by that year (1979-01-01)? Thus eliminating the need for additional spin-up?

Thanks in advance for any suggestions/clarifications/help.

 

[katec]

So, the run may be doing something you don't expect here. In the documentation here: 5. Running a Case — CIME master documentation

In a branch run, all components are initialized using a consistent set of restart files from a previous run (determined by the $RUN_REFCASE and $RUN_REFDATE variables in env_run.xml). The case name generally is changed for a branch run, but it does not have to be. In a branch run, the $RUN_STARTDATE setting is ignored because the model components obtain the start date from their restart data sets.

So, even though the case says the Start Date is 1979, the model will actually start from your restart files date of 1955. No need to "spin up" between the two years.