Aspects of the Load Circulation at the Grand Canyon during the Fall Season

Abstract

The atmosphere and circulation of air within, above, and around the Grand Canyon of the Colorado River was studied from an instrumented aircraft and from ground-based instruments in September and October 1984. Several patterns were identified. The nighttime formation of stabilized layers and infrared cooling did not necessarily guarantee a downslope and a downstream flow. Morning observations showed early formation of thermal patterns which increased during the day until, under clear skies, turbulent mixing would disrupt the stable layers above the canyon in September. October solar heating seemed insufficient to totally disrupt the stable layers above the canyon, and only limited areal segments displayed instability at the rim level. The depth of the turbulent mixing is a function of sky cover and cloud thickness. The amount of influence of the large-scale air motion depends on the orientation of the canyon relative to the direction of this motion.