I ran two sets of RegCM simulations.

One with dt=150 450, the other with dt=180 540. The other parameters

of them are same.(dx=60)

I found the output of them quitely differentiate.

For example, the groud temperature difference of above two simulations

have reached up to 5 degrees over some areas.

Which is right? dt=150 or 180?

Does it mean that we should change dt for several times to choose the best

step by comparing with CRU?

Best regards,

Libin Yan