An Observational and Numerical Study of a Regional-scale Downslope Flow in Northern Arizona

During the month-long METCRAX field campaign in northern Arizona near Winslow in October 2006, observed wind profiles uncovered a frequent presence of a nearsurface wind maximum on nights with relatively quiescent synoptic conditions. The development of this flow usually began shortly after sunset with a shift from disorganized wind directions accompanying weak winds in late afternoon to a more steady southwesterly flow which continued through the night. The month-long observations from various measurement platforms are used to characterize the structure and evolution of this flow and numerical model simulations using the RAMS model are used to help identify the forcing mechanisms. The model results, which compared reasonably well with the observations, suggest that this low-level wind maximum represents a regional-scale downslope flow developed over the Coconino Plateau that slopes up towards southwest of the observational site near Winslow.