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Required simulation time to get PBL results

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I'm interested in obtaining PBL (planetary boundary layer) related data; mainly the distribution of PBL height and vertical velocity profile with time. In terms of time and length scales: I'm after the velocity profiles in the first 150-200 meters for a timespan of ~ 1 hour over a 5km x 5km domain.
My understanding is, PBL parameters start with 0 and require a certain amount of time to fully develop in WRF simulations. But I'm not sure what would be an optimal simulation time before starting to collect such usable PBL data. I'm used to running a 6-hours simulation before collecting the 1-hour data that I need, but I'm not sure if it is overkill or completely insufficient.
Can you please kindly advise? Do you have any rule of thumb, or an optimal run time, based on your experiences?
Greatly appreciate your help.
I guess you are asking how long the spinup time should be before you can get more reasonable results.
Usually 6-9 hours will be sufficient for the model to finish adjustment. There is no strict rule to determine when the spin-up is ready. But you can always compare your simulations with observations and decide what period can be treated as the model spinup time.
Mr. Ming Chen,
Thanks for your input. I was expecting that it would depend on the length and time scales of the simulation, but starting with 6-9 hours and validating is indeed a good idea.