Lightning investigation at high altitudes in Colorado

THE operation of transmission and distribution lines in the high altitudes of the Rocky Mountain region had indicated that lightning strokes were not so severe as at lower altitudes. Also glow discharges or corona currents from the earth have been observed at high altitudes from pointed objects and rocks. This investigation was made to determine the probable lightning current at altitudes from 6,000 feet to 13,500 feet and to measure corona current. It has been found that the probable stroke current decreases with increase of altitude from sea level to approximately 18,000 feet altitude at which point it appears that no current would be present. The highest mean temperatures at 18,000 feet do not exceed 32 degrees Fahrenheit, and comparison of temperatures in free air at altitudes up to 13,500 feet check temperatures on the earth's surface and indicate that freezing temperatures may limit the formation of lightning.