Scientists study ways to tame hurricanes

Every year, about the time of the first big storm, the calls and e-mails from concerned citizens into the National Hurricane Center in Miami pick up a bit.While most have questions about storm tracks and warnings, a few have suggestions about how to turn away -- or turn down -- the wrath of a cyclone.The ideas range from blowing storms up with bombs (nuclear or otherwise), to cooling off the warm tropical waters that sustain hurricanes by floating icebergs into the projected path, to setting up banks of giant fans to blow the storm back to sea.Invariably, if the forecasters and technicians have time to discuss the propositions, they mention the basic shortcoming of all the ideas."They fail to appreciate the size and power of tropical cyclones," says Christopher Landsea, the science and operations officer for the center and a noted hurricane researcher.A mature hurricane releases heat equivalent to a 10-megaton nuclear warhead exploding every 20 minutes. The center of the storms -- the eye and the ring of thunderstorms around it that make up the eye wall with the strongest wind -- is often 20 miles wide, and the effects of hurricanes typically extend hundreds of miles from the centers.Delivering enough energy or chemicals to reduce the heat or water-vapor content of a large storm has, in fact, often been considered, measured and even attempted several times with small fleets of military aircraft, only to be dismissed as colossally impractical.But now, as the human toll rises and the damage from even moderate tropical storms and hurricanes mounts into tens of billions of dollars already this season -- with the potential for several more hits this month alone -- some scientists are convinced it's worth another try to study ways to weaken or divert storms.A difference of 30 or 40 miles an hour in hurricane winds can determine whether most roofs stay put or blow away in an affected area. And a track shift of 40 or 50 miles by Hurricane Gustav this week meant the difference between a close call and another inundation for New Orleans.The potential payoff is so great, the scientists may convince the Department of Homeland Security to spend a couple million dollars to run some computer models and small, lab-scale experiments on several of the more promising techniques."We're not talking about going out and seeding clouds, but doing some limited research on some things that could have a huge impact," said Joe Golden, a scientist at the Cooperative Institute for Research in Environmental Studies at the University of Colorado at Boulder.Weather modification in the form of cloud seeding has been around for decades, with scientists around the world able to wring rain from reluctant clouds most, but not all, of the time.But tropical storms are a vital part of Earth's climate controls, part of the oceans' constant exchange of heat from the equator toward the poles. Some regions, including the southeastern United States, get much of their water supply out of rainfall from the storms. So steering a storm away from a stretch of coastline might not get cheers from everyone.One 1947 test, which involved an Air Force bomber's dropping 180 pounds of dry ice into a storm off South Carolina, was later blamed for causing the hurricane to stop moving away from the coast and turn back to strike Savannah, Ga. Weather officials eventually determined that the turn came before the dry ice was applied."I know it's very controversial, but as a scientist and as a citizen, if we have the slightest chance to doing something beneficial without harming the environment or causing some unexpected consequences, we owe it to the taxpayers to give it our best shot," said Golden, a veteran of the government's last venture into hurricane control, called Project Stormfury.Stormfury, run by the National Oceanic and Atmospheric Administration, shut down a quarter-century ago. It was the last and biggest of several programs launched after World War II to seed hurricanes with silver iodide in a bid to weaken and stall them out. While some changes were noted after the seeding, experts now believe the storms were simply going through natural fluctuations, such as eye-wall replacement, that the knowledge and instrumentation of that era didn't take into account.Partly because of all the flights into hurricanes made during Stormfury and thousands of forecast and research flights since, Golden says, scientists today have a much better sense of how the storms work -- and are better able to spot minute changes that modification might produce."It's a convergence of things -- better radar, satellites, better instruments in our aircraft, much faster computers and better models to take all this data and simulate hurricanes," Golden said. "All this puts us in a better position to evaluate various concepts."Last fall, Golden and others successfully pitched the notion to Jay Cohen, head of Homeland Security's Science and Technology Directorate, that the department should get a group of experts together to develop a research agenda for hurricane modification.That group met in Boulder in February and produced a report calling for $1.6 million to be spent on modeling before choosing three or four approaches for detailed tests. No large-scale tests are envisioned for at least six or seven years.Homeland Security has yet to move on the proposal, but Cohen told a congressional hearing earlier this year that while such projects are risky, "they offer the potential for leap-ahead gains in capability, should they succeed."Among the concepts that would be modeled: several new approaches to seeding clouds with sea salt or Saharan dust; applying a carbon-black aerosol to the tops of hurricanes to shut down their ventilation; and several ideas to pump deeper cold water or apply a biodegradable barrier in the sea ahead of a developing storm to rob it of warmth.And, Golden says, even if none of the technologies can divert or weaken a hurricane, "we may develop better ways to predict where storms will make landfall and at what intensity."On the Net: http:/www.noaa.govwww.dhs.gov/xres/(Contact Lee Bowman at bowmanl(at)shns.com.)