Definition of spin up

Dear all;

Could you explain to me what is simulation “spin-up”? Appreciate it!


One hopes that as a simulation proceeds, its state gets closer and closer to “reality”, even if the model’s initial conditions were quite bad. The simulation-period before the model-state is sufficiently close to reality is the spin-up period.

How long this takes depends upon a lot of things, including the type of model and its resolution (as well as how close the initial conditions were to reality). For meteorology models, this typically takes only a few simulation-hours; for air quality models, a few simulation-days; and for hydrology (ground-water) or river-sediment models it takes a few simulation-years (or decades (!), in bad cases)…

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