Abstract/Summary

Charge influences the properties of liquid droplets, such as evaporation rates, hydrodynamic stability and sticking probabilities. Modifying droplet charge therefore provides a possible method of influencing fogs or clouds. An instrumented, remotely piloted aircraft has been equipped with positive and negative corona emitters to cause droplet charging. With the aircraft circling at 20 m altitude, effects of ion release were compared in clear air and natural fog. In clear air, the surface atmospheric electrical field changed whenever the emitters were activated, but without significant differences in the short-wave radiation as the aircraft passed over previously ionized air. In fog, radiation fluctuations showed a Gaussian distribution before either emitter operated and when both emitters were operating, but with different distributions during unipolar ion emission. Introducing unipolar ions led to a maximum change in fog reflectivity of ~2%, about 25 s later.