The Hairy Issue of Hurricane Modification
When last we met, authorities had approved the audacious proposal of a brash young meteorologist to save Miami from the devastating effects of Hurricane Calamity.
Needless to say it didn't work, but at least there was enough leftover Prozac for the local, state and federal officials to somewhat relieve their dread of impending disaster and feeling of helplessness to prevent it.
While I await an offer for the movie rights to this fictional tale, let's get back to the real world of possibilities for modifying hurricanes in ways that would reduce the potential loss of life and property.
Keep reading for more on hurricane modification. For local weather, see our full forecast through the weekend.
Project Cirrus in the late 1940s and early 1950s and Project Stormfury in the 1960s and '70s were two of the earliest attempts to modify hurricanes. Without getting too geeky, the fundamental approach was to seed clouds within specific regions of a storm with tiny particles of silver iodide or dry ice, providing surfaces around which moisture can collect and condense. Promoting and accelerating condensation of water vapor into raindrops, it was thought, would change the distribution within the storm of the heat energy released when water changes phase from gas to liquid. In principle, this could lead to changes in the storm's structure, intensity and motion, because it is this heat energy (known as latent heat) that fuels and drives hurricanes.
As it turned out, some hurricanes seeded in Projects Cirrus and Stormfury did indeed appear to undergo fairly rapid changes in strength and/or motion. The initial gee-whiz excitement and optimism of these experiments, however, proved unjustified. The problem here, as with virtually all weather modification efforts, is the inability to distinguish confidently between changes due to human intervention and those which occur naturally.
For example, in Project Cirrus, a storm that appeared to be moving out to sea suddenly changed direction -- seemingly in response to seeding -- and made landfall near Savanna, Ga., causing extensive damage. But it was later discovered that the storm's shift in direction actually occurred shortly before seeding began and was instead due to changes in the upper-level steering winds.
In Project Stormfury, the working hypothesis was that cloud seeding could be used to expand the diameter of the hurricane eye by replacing the existing eyewall with one further from the storm center. The net result would be to reduce the difference in pressure between the storm center and eyewall and, consequently, decrease the intensity of winds around the eye. So far so good. However, it was later recognized that these so-called eyewall replacement cycles are a natural part of a hurricane's evolution, making it virtually impossible to distinguish between changes in the storm due to seeding and those that would have happened naturally.
Serious efforts to explore hurricane modification waned considerably after the end of Project Stormfury. That is until renewed interest was sparked by the destruction and loss of life wrought by hurricanes Katrina, Wilma and Rita in 2005. Last February, National Oceanic and Atmospheric Administration hosted a workshop sponsored by the Department of Homeland Security to identify and evaluate the feasibility of new approaches for modifying hurricanes. Among the options considered by scientists were creating oil slicks to slow evaporation and heat transfer from ocean to atmosphere; decreasing instability in the atmosphere by warming the upper layers of the hurricane with what amounts to spray painting cloud tops black with some kind of soot, causing the clouds to absorb more heat from the sun and thus reducing the vertical change in temperature in the atmosphere; and deploying floating buoys designed to cool the sea surface by pumping warm surface water down and drawing cold water up.
Although these ideas are not as totally nonsensical as the approach illustrated in the cartoon above -- in principle, it's conceivable they might succeed in altering hurricanes in one way or another -- I doubt they will ever be employed, except possibly in computer simulations. As with Projects Cirrus and Stormfury, it would be difficult to directly attribute changes in hurricane behavior to such efforts. Not to mention the cost, technical and logistical challenges, and ecological considerations would be extremely prohibitive.
And then there's the legal factor. Steering a storm away from Miami, for example, to a less-populated region could destroy towns that otherwise might have escaped damage. Or, tinkering with a hurricane could weaken it or cause it to completely miss an area in need of drought-busting rainfall? Just imagine the blizzard of civil suits and prolonged litigation that would likely ensue.
Finally, one cannot ignore the law of unintended consequences. Hurricanes are a vital instrument in the global balance of heat and moisture in the atmosphere and oceans and, therefore, play a critical role in the overall climate system. Science has shown that humans already are having a profound impact on Earths' climate. Fooling any further with Mother Nature may only compound our problems.
| October 23, 2008; 11:00 AM ET
Categories: Tracton, Tropical Weather
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