Droplet charging by high voltage discharges and its influence on precipitation enhancement

Laboratory experiments were performed to determine the effect of electrical charges transferred on droplets by electrical discharges on their growth by collision and coalescence. A twin cloud chamber was built inside a large cold room and was filled with cloudy air. One chamber was used as the control chamber and, therefore, was left unperturbed. On the other hand, in an experimental chamber, electrical discharges were produced. Droplets grow during a free fall of 1 m, and the droplet spectrum was sampled by microscope slides covered in Formvar. The experimental arrangement could also measure charge on individual drops between 325 and 415 μm in diameter by using small induction rings. comparing the spectra from both chambers, a shift towards larger sizes was observed in the cloud that sustained electrical discharge. Also, by measuring the charge on the droplets, it could be observed that the electrical discharge transferred charges of both signs. Discussions about the relevance for cloud seeding and fog elimination are carried out.