Superior-Mirage Photographs: Evidence of Complex Air Temperature Profiles in Sonoran Desert Valleys

The literature of sightings of superior and inferior mirages in various areas of the western deserts of North America and of current understandings of mirage phenomena are reviewed. Photographs are used to discuss several superior mirage images observed in late autumn 1985 and in winter 1986 in the course of travel on U.S. Highway-89 from Tucson, AZ., into the Falcon Valley (shown on a map). The meteorological data on atmospheric temperature and wind, associated with these mirages, are described; and upper air soundings of temperature above Tucson Airport are given in a graph. Strong temperature-inversion conditions ( similar to 0.02 degrees C m super(-) super(2) ) were observed at 1200 hr G.M.T. to a height of similar to 350 m (relative to the airport elevation of 787 m a.s.l.). Upper air winds were generally south-southwesterly; thus, the radiosonde may have passed over the general area of the mirage similar to 1-2 hr before the sighting of the mirages. Surface conditions in the general area of the mirage were influenced strongly by local terrain effects and a lack of cloud cover, and were similar to conditions at the Tucson Airport in the Tucson Valley, south of the Falcon Valley. The authors believe that the surface-air-temperature inversion above Tucson Airport may have been similar in magnitude to the inversion in the area of the mirage sighting because of similarity of terrain and close proximity of the areas.