Accelerated decay of thunderstorm electric fields by chaff seeding

Abstract

The field decay experiment conducted during the summer of 1972 in Colorado by the Atmospheric Physics and Chemistry Laboratory of the National Oceanic and Atmospheric Administration may be considered as the first experimental step to lightning suppression by chaff seeding. An airplane equipped with an electric field measuring system and a chaff dispenser flew underneath a developing thunderstorm, continuously monitoring the electric field. If the field exceeded 50 kV m−1, chaff was dispersed during the next two passes underneath the cloud, and the field decay was recorded until the storm dissipated. Each seeded storm was matched by a control (unseeded) storm to obtain the field decay rate under normal conditions. The field tests showed that chaff seeding in moderate fields of 50 kV m−1 accelerated the field decay by a factor of 5. In one case a stronger field of 300 kV m−1 was seeded, and the field decay rate was faster by a factor of 10 than that of the seeded storms having moderate fields. The physical background of this process, its limitations, and its significance to the problem of lightning suppression are discussed.