A new experiment has shown that zapping clouds with electrical charge can alter droplet sizes in fog or, potentially, help a constipated cloud to rain.
Last year Giles Harrison, from the University of Reading, and colleagues from the University of Bath, spent many early mornings chasing fogs in the Somerset Levels, flying uncrewed aircraft into the gloop and releasing charge. Their findings, published in Geophysical Research Letters, showed that when either positive or negative charge was emitted, the fog formed more water droplets.
“Electric charge can slow evaporation, or even – and this is always amazing to me – cause drops to explode because the electric force on them exceeds the surface tension holding them together,” said Harrison.
The findings could be put to good use in dry regions of the world, such as the Middle East and north Africa, as a means of encouraging clouds to release their rain. Cloud droplets are larger than fog droplets and so more likely to collide, and Harrison and his colleagues believe that adding electrical charge to a cloud could help droplets to stick together and become more weighty.