Presumably in honor of Hurricane Sandy, folks at the Popular Science website dug up an old article published in PopSci magazine back in 1956 (you can read it here). The article details a plan to seed growing hurricanes with dry ice, an idea which was the brainchild of scientists at the government-sponsored National Hurricane Research Project in ‘an all-out search for the causes and cures of hurricanes’. (For the record, dry ice is in no way related to frozen water- it is really just cold, solid carbon dioxide. The ‘dry’ refers to the fact that as it ‘thaws’ it simply sublimates, transitioning straight from a solid phase to a gas phase.) Seeding hurricane clouds, they believed, may help them to divert hurricanes away from land and populated areas to minimize their destructiveness. Their hypothesis became the foundation of what would later become Project STORMFURY.
The idea of using dry ice to divert hurricanes was based on the principles of cloud seeding. ‘Cloud seeding’ is carried out by sprinkling cherry-sized pellets of dry ice on a cloud which is at a temperature below freezing. As dry ice meets cloud vapor tiny ice crystals are formed, and nearby water droplets nucleate on the tiny ice crystal. As the ice crystals grow they form snowflakes which become so heavy that they fall straight to the earth, eventually melting into rain as they travel through the atmosphere into warmer temperatures. The technique, however, is not specific to dry ice, as silver iodide eventually proved to be a more attractive nucleating agent. Dry ice was eventually thrown out altogether in favor of silver iodide, which has a molecular structure resembling ice. (Here’s a fun piece of trivia: The scientist who discovered that silver iodide could be used as a nucleating agent was none other than Bernard Vonnegut, Kurt Vonnegut’s brother. In Cat’s Cradle, Vonnegut [the author] mentions ice crystallography, presumably inspired by his brother’s work.)
|Cartoon of the 'STORMFURY hypothesis'. Image credit: National Oceanic & Atmospheric Administration|
Ultimately, researchers hoped that if enough of the clouds ‘fell away’ as rain, the storm center may be shifted enough that it would change the direction of the storm. By seeding the clouds of a growing tropical storm or hurricane, researchers speculated, they could potentially guide the storm away from land and onto the open ocean or at the very least attenuate the strength of the hurricane’s winds.
The government experimented with the method detailed above using silver iodide instead of dry ice, but the efficacy of cloud seeding as a storm ‘deterrent’ was never established. Project STORMFURY was finally discarded in the 1980s because it was unclear whether scientists’ interventions were actually making an impact on the course of the storms, and because it appeared that there was not nearly enough supercooled water in the hurricane clouds for the seeding agent to act on and too much natural ice.
Even today, cloud seeding as a method of producing precipitation in drought-ridden areas remains controversial. Even though Project STORMFURY ultimately went the way of the dinosaurs, it remains a testament to the ingenuity of scientists- and a testament to the indomitable strength of Mother Nature. (Fifteen minutes ago, I was reminded anew- a thirty foot tree is now strewn across my lawn, a sacrifice to Miss Sandy).
For a more detailed overview of Project STORMFURY and the results yielded by researchers working on the project, you can read this 1985 publication.
And FYI, New Jerseyans, according to Gov. Christie an executive order to reschedule Halloween this year will be filed in wake of Hurricane Sandy. Go figure.
|Gratuitous satellite image of Hurricane Sandy. Image credit: NOAA|