Surface Temperature Inversions in a Canyon

Abstract

A micrometeorological investigation was made of ground layer inversion formation, maintenance, and dissipation, and of the related thermal circulations as they were observed in and near the mouth of Red Butte Canyon in the Wasatch Range of northern Utah. Measurements of temperature and other parameters at various locations and levels were made near the mouth of the canyon by means of a semi-automatic instrument and recording network. Analysis of data obtained during the summer of 1957 showed that one basic pattern occurred on 90 per cent of the days. Detailed study of this basic pattern revealed the following significant features: 1) The formation of a thin film of cold air within the canyon an hour or two before (astronomical) sunset. 2) A definite wind shift from up-canyon to down-canyon within about 10 min, near the time of sunset. 3) Extremely rapid local cooling and increase in wind speed near the canyon mouth for about half an hour after the wind shift. 4) Quasi-steady wind and little cooling in the canyon within the first hour after the wind shift, although outside the canyon moderate cooling lasted several hours.