Could cloud-seeding weaken hurricanes?

Researchers propose cloud-brightening to avert strong storms

A composite NOAA image of Hurricane Andrew, in 1992.

By Summit Voice

SUMMIT COUNTY — While hurricanes are often feared as a destructive force of nature, they are also one of nature’s great climate regulators, helping to disperse ocean and atmospheric heat away from the equatorial region.

But some environmental scientists think it might be a good idea to reduce the intensity of hurricanes by seeding clouds to decrease sea surface temperatures when hurricanes form. Theoretically, the scientists claim the technique could reduce hurricane intensity by a category.

The team focused on the relationship between sea surface temperature and the energy associated with the destructive potential of hurricanes. Rather than seeding storm clouds or hurricanes directly, the idea is to target marine stratocumulus clouds, which cover an estimated quarter of the world’s oceans, to prevent hurricanes forming.

“Hurricanes derive their energy from the heat contained in the surface waters of the ocean,” said Dr Alan Gadian from the University of Leeds. “If we are able to increase the amount of sunlight reflected by clouds above the hurricane development region then there will be less energy to feed the hurricanes.”

Along with dispersing summer heat, hurricanes also play an important role in the maintenance of many marine ecosystems, including mangrove-coral atolls, where the storms help clean away sediment. In some cases, they help build new land areas.

Nevertheless, the University of Leeds team says it could be worth pursuing the idea of weakening hurricanes if it can be shown that there would be no adverse impacts, including affects such as reduced rainfall in other areas.

“Much more research is needed and we are clear that cloud seeding should not be deployed until we are sure there will be no adverse consequences regarding rainfall,” concluded Gadian. “However if our calculations are correct, judicious seeding of maritime clouds could be invaluable for significantly reducing the destructive power of future hurricanes.”

The researchers propose using marine cloud brightening, which has also been eyed as a way to reduce large-scale global warming. Under their theory, unmanned vehicles could spray tiny seawater droplets, a good fraction of which would rise into the clouds above, increasing their droplet numbers and thereby the reflectivity and duration of clouds. That would bounce more sunlight back into space and reduce sea surface temperature.

“Data shows that over the last three decades hurricane intensity has increased in the Northern Atlantic, the Indian and South-West Pacific Oceans,” said Gadian. “We simulated the impact of seeding on these three areas, with particular focus on the Atlantic hurricane months of August, September and October.”

The calculations show that when targeting clouds in identified hurricane development regions the technique could reduce an average sea surface temperature by up to a few degrees, greatly decreasing the amount of energy available to hurricane formation.

One potential drawback to the idea is the impact of cloud seeding on rainfall in neighbouring regions. The team noted concerns that seeding in the Atlantic could lead to a significant reduction of rainfall in the Amazon basin and elsewhere. However, if different patterns of seeding were used, such rainfall reductions were not found over land.

 

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One Response

  1. James Fleming’s book Fixing the Sky: The Checkered History of Weather and Climate Control explored historical attempts to weaken hurricanes with cloud seeding in the past. Mostly didn’t work, although if I recall correctly there was one instance where they might have influenced a hurricane to change course 180, towards land! Oops. One can see the potentially massive liability issues there.

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