Diurnal and seasonal wind direction patterns within the Mountain-Valley Terrain near Glen Canyon Dam, Arizona.

Surface and upper air wind measurements were taken over the past several years near Glen Canyon Dam, Arizona as a part of a multiyear visibility study in the region. Analyses of the wind direction data reveal the existence of two primary flow regimes throughout the diurnal cycle. At night, the wind directions show a propensity for southwesterly flow 180 m above the canyon floor; daytime surface winds are reversed with a strong northeasterly component. These two dominant surface patterns found throughout the year may be associated with return flow circulation from the expected wind pattern near the valley floor. However, a local wind pattern induced by temperature differences between bearby Lake Powell and the surrounding landscape may explain the observed patterns. During the summer season, a third regime apparently associated with afternoon convective mixing exhibits a secondary tendency for southwesterly winds. If the wind patterns recorded at the two Glen Canyon Dam sites are associated with return flow (as opposed to a lake induced circulation), the results from this investigation are similar to the wind fields from comparable observational and modeling studies.