An Evaluation of Some Thermal Fog Dispersal Experiments

Abstract

Thermal fog dispersal tests were conducted by the Air Force Cambridge Research Laboratories during July 1972 at Vandenberg AFB, California. The experimental heating system consisted of an array of passive liquid propane burners that were arranged in four lines perpendicular to the prevailing wind. An instrumented 200 ft tower and a lidar were used to monitor the effects of the tests on the foggy environment. The heating tests were designed to simulate fog dispersal operations at an airport under cross-runway wind conditions. The effect of wind speed and heat output on the temperature, visibility and turbulence structure of the environment are discussed. The test results confirmed the earlier findings of the British FIDO program during WW II with respect to the characteristic temperature rise pattern for a cross-wind situation. The program documented visibility improvements in the heat plumes that could only be inferred from the published FIDO temperature rise data. Extrapolating the results of these experiments to a similar system installed at an airport, it appears that the visibility improvements that were achieved in the experiments would always be adequate for Category 2 (100 ft decision height, ¼ mi visibility) and 3A (no decision height, ? mi visibility) landing operations. Category 1 (200 ft decision height, ½ mi visibility) landing conditions could be achieved by increasing the heat output of the burners.