Abstract/Summary

Electric charge is always present in the lower atmosphere. If droplets or aerosols become charged, their behaviour changes, influencing collision, evaporation and deposition. Artificial charge release is an unexplored potential geoengineering technique for modifying fogs, clouds and rainfall. Central to evaluating these processes experimentally in the atmosphere is establishing an effective method for charge delivery. A small charge-delivering Remotely Piloted Aircraft has been specially developed for this, which is electrically propelled. It carries controllable bipolar charge emitters (nominal emission current ±5 µA) beneath each wing, with optical cloud and meteorological sensors integrated into the airframe. Meteorological and droplet measurements are demonstrated to 2 km altitude by comparison with a radiosonde, including within cloud, and successful charge emission aloft verified by using programmed flight paths above an upwards-facing surface electric field mill. This technological approach is readily scalable to provide non-polluting fleets of charge-releasing aircraft, identifying and targeting droplet regions with their own sensors. Beyond geoengineering, agricultural and biological aerosol applications, safe ionic propulsion of future electric aircraft also requires detailed investigation of charge effects on natural atmospheric droplet systems.