Research and Development

Aerial Electrostatic Weather Modification System

The Issue

The efficiency of the collision and coalescence of droplets is reduced when  cloud condensation nuclei (CCN) are in the form of dust, aerosols and/or pollutants. These CCN’s are very small and usually are hydrophobic. Therefore, these cloud droplets are very small resulting in a lack of collision and coalescence and instead tend to bounce off of one another instead of growing into a larger droplet. Furthermore, due to the shape and size, these droplets will not freeze and will become supercooled. This limits the amount of ice in a cloud which is a main component for precipitation in convective clouds. Secondly, with a limited number of droplets freezing, the latent heat released from the phase change is lessened which results in a shorter storm period with lower cloud tops and an overall less efficient cloud. 

Modified Electrostatic system on a Comanche aircraft.

The Solution

The USDA-ARS has patented an electrostatic system capable of charging droplets out of an agricultural aircraft. The technology only uses tap water, rather than silver iodide or calcium chloride. As the droplets are released from the nozzles, an electrostatic charge is applied to the droplets. Using the inflow of a convective thunderstorms, a high concentration of large charged droplets is transported into the warm cloud layer. The large droplets, with an electrostatic charge, take over the small cloud droplets and result in a more efficient warm rain process. These larger droplets will then reach the freezing level of the storm and change phase from liquid to ice. This will provide plenty of ice in the low portion of the cold cloud layer, breaking up and falling as precipitation. While this takes place, latent heat is released allowing the cloud to grow vertically and last longer. This technique has been shown to double the amount of additional rainfall generated compared to conventional cloud seeding methods, at a much lower operating cost.

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