Scientists electrically charge ‘constipated’ clouds to make them rain

A new scientific experiment has proven that electrically charging clouds can change the size of the droplets in fog or, possibly, droplets in a cloud that is having trouble moving to fall as rain.

The new experiment assists a "constipated cloud" in becoming rainy, according to a report published by The Guardian on Thursday.

"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 Giles Harrison, lead author, professor of atmospheric physics in the department of meteorology at the University of Reading, U.K.

Harrison and his colleagues contend that giving a cloud an electrical charge can help the droplets adhere to one another and accumulate weight since cloud droplets are larger than fog droplets and are thus more likely to collide.

The tests saw the drone fly in a circular, horizontal pattern over a measurement site where the electric field and droplet characteristics were recorded.

The UAV's positive and negative charge emitters were turned on alternately. An onboard optical sensor in a fixed location gazing down was monitoring changes in visible radiation below. The observed radiative responses were divided into groups according to the various operating emitter combinations for study.

More water droplets formed in the fog when either a positive or negative charge was released, according to their research.

The experiment

The experiment noted that the release of unipolar ions into a fog by a UAV is connected to brief changes in the fog's reflectance and radiative characteristics. The droplet size distribution largely determined these characteristics.

Thus, variations in the droplet size distribution caused by charges explained the radiative changes. Bipolar ions, in contrast to unipolar ions, resulted in a relatively low mean droplet charge but speeded up the process of reaching a steady-state charge distribution.

The experiment's results purport to demonstrate for the first time drone charge release into the fog, potentially revealing a new route to influence cloud and fog without leaving behind chemical byproducts, which are normally used in cloud seeding.

The research could be used to help clouds release rain in arid places of the world like the Middle East and North Africa.

Cloud seeding

A substance called silver iodide (AgI) is typically used in cloud seeding procedures to help ice crystals develop, making rain. Low amounts of silver iodide are found naturally in the environment, having no negative effects on living beings.

Despite the future-sounding humans "managing the weather," cloud seeding has a lengthy history dating back to 1946 when General Electric research facilities induced snowfall close to Mount Greylock in Massachusetts.

Over 50 programs have been identified by the National Oceanic and Atmospheric Administration (NOAA), which keeps track of cloud seeding activities in the U.S., since 2000.

These initiatives get a lot of cash from the government. Utah spends up to $700,000 yearly on one of the biggest cloud-seeding initiatives in the U.S. The acting director of the state's Department of Natural Resources recently appeared to promote cloud seeding as a new strategy to try and save the Great Salt Lake.

The new experiment, however, offers an alternative to cloud seeding, making it rain close to more naturally than ever.

The findings of the experiment/study were first published in Geophysical Research Letters on September 3.

Study abstract

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 or 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.