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While the Gulf Coast was pounded with hurricanes last year, the southwestern part of the United States continued to suffer in the grip of a long, many-year drought.

This has led some people to think about how we might actively modify the weather: steer hurricanes clear of land, perhaps, or bring rainfall to parched farmlands.

People have been trying to alter the weather for thousands of years. From virgin sacrifices to firing cannons into the air, nothing worked — until Nov. 13, 1946, when a trio of General Electric scientists made snow fall out of a cloud over Mount Greylock, Mass.

“This is history!” exclaimed their leader, Nobel laureate Irving Langmuir. The other two scientists were Vincent Schaefer and Bernard Vonnegut — whose brother, Kurt, would later become a world-renowned author of science fiction.

The technique they had developed was cloud seeding.

Clouds are composed largely of water vapor and water droplets: that is, water in its gaseous form, and water in its liquid form. Water vapor can change into droplets when there are microscopic particles in the cloud.

Under the proper temperature conditions, the water vapor can begin to condense around these particles and form droplets of liquid water.

These microscopic particles are called condensation nuclei. They can be bits of dust, grains of sand, even fine ash from fires on the ground.

As the vapor in a cloud condenses into droplets, swirling air currents within the cloud make small droplets merge into bigger droplets. The cloud gets darker.

Eventually, the drops become too big and heavy to stay aloft. Raindrops fall. Or, if it is cold enough, the droplets freeze into crystals and snow falls out of the cloud.

The team of Langmuir, Schaefer and Vonnegut hit on the idea of seeding potential rain clouds with particles of silver iodide that could serve as condensation nuclei. If the seeding is done properly, a cloud can be made to produce rain. Or snow, as was done at Mount Greylock.

It’s a tricky business. You can’t produce rain out of a clear sky, but cloud seeding does allow you to squeeze some extra rain out of a cloud, perhaps 10 or 15 percent more rain than the cloud would have yielded if it hadn’t been seeded.

Once it became known that cloud seeding works — under the right conditions — rainmaking became a business. And a storm center of controversy.

In the western parts of the United States, rainfall is precious, and droughts are not uncommon. Professional rainmakers have been seeding clouds for decades, often being paid on the basis of the number of inches of rain produced per acre of ground. Often nothing happens, despite the seeding. Conditions must be just right for seeding to produce precipitation.

And how do you know that the rain that fell on your farmland was produced by the cloud-seeding operation, and not just plain old natural rainfall?

Rainmakers have been sued for failing to produce rain, and sued for causing floods. Farmers have sued rainmakers for robbing them of rain that would have fallen on their acres if the @#$%&* rainmaker hadn’t made it fall on the farm a few miles away.

While university scientists have tried to learn how clouds work and to understand the physics behind cloud seeding, professional rainmakers have eked out a precarious living and battled lawsuits.

Last year, the state of Wyoming announced it would fund a five-year, $9 million pilot program aimed at increasing the snow pack on the Medicine Bow, Sierra Madre and Wind River mountain ranges. A heavier snow pack means more water available in the spring and summer.

By seeding the moisture-laden clouds that build up in the winter, Wyoming officials hope to find a way to relieve the drought that has plagued their state for many years.

Unlike the cloud seeding operations of most professional rainmakers, the Wyoming program is being planned as a scientific experiment. Scientists from the National Center for Atmospheric Research will evaluate the effort, not the cloud seeders themselves.

Can a determined, well-planned, multi-year cloud seeding program help to ease a long-standing drought? Time will tell.

Meanwhile, in the wake of the disastrous 2005 hurricane season, several schemes for dealing with these enormous storms have been proposed.

One idea is to lay down an oil slick on the ocean’s surface in the path of an oncoming storm. The goal is to prevent the hurricane from sucking up the warm sea water that is the storm’s source of energy. Problem is, though, that a hurricane whips up the sea so badly that the oil slick would be quickly demolished.

Another possibility is using squadrons of airplanes to drop water-absorbing chemicals into the hurricane. This would dry out the clouds, which in turn would make the storm system collapse. The technique has worked on small thunderstorms. Hurricanes are much larger and more powerful. How much of the chemicals would be needed, assuming that the technique could work?

A quarter century ago, the National Oceanographic and Atmospheric Administration (NOAA) tried cloud seeding on hurricanes. Only storms that were far from land were seeded, for fear that the seeding might backfire and strengthen the hurricane or perhaps steer it toward populated areas. The results were not clear-cut: seeding appeared to lower wind speeds in the storms’ eye walls, but only temporarily.

Hurricanes are immense heat engines that release a megaton of energy every 15 minutes or so. Dropping a nuclear bomb into a full-grown hurricane would only make it stronger!

But scientists are still trying to find a way to handle these storms. We don’t have the brute strength to conquer hurricanes, but perhaps — in time — we will have the smarts to at least steer them away from populated region such as the Gulf Coast.

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Hurricane Wilma survivor Ben Bova is the author of more than 100 books, including “Mercury,” the latest novel in his acclaimed Grand Tour series. Dr. Bova’s Web site address is www.benbova.net.