@ William: DFI is "Digital Filter Initialisation". You can find that option in the reference namelist under "dfi_control". From the WRF manual:
"Digital filter initialization (DFI) is a way to remove initial model imbalance as,
for example, measured by the surface pressure tendency. This might be important
when one is interested in the 0-6 hour simulation or forecast. It runs a digital
filter during a short model integration, backward and forward, and then starts the
simulation. In the WRF, this is all done in a single job."
In theory, this should reduce the spin-up time (although from my own experiments, I can't say I have noticed much of an effect). It will also, of course, increase the model runtime.
"Digital filter initialization (DFI) is a way to remove initial model imbalance as,
for example, measured by the surface pressure tendency. This might be important
when one is interested in the 0-6 hour simulation or forecast. It runs a digital
filter during a short model integration, backward and forward, and then starts the
simulation. In the WRF, this is all done in a single job."
In theory, this should reduce the spin-up time (although from my own experiments, I can't say I have noticed much of an effect). It will also, of course, increase the model runtime.