Atmosphere And Weather

Cloud Seeding an Overview



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The 2008 Opening Ceremonies of the Beijing Olympics went off without a hitch. Beautiful venue. Beautiful performances. And a beautiful night. The Chinese put a lot of effort into every aspect of the event - including controlling the weather.

Does this mean that they provided umbrellas, ponchos and shelter in case inclement weather should break out? No. It means they went to the skies and sought to keep the inclement weather away from that night altogether. They started cloud seeding.

WHAT IS CLOUD SEEDING?

Cloud seeding can change the weather by bringing on and even changing precipitation. It can reduce fog and hail, increase the amount and intensity of rain, and result in the break up of clouds so that areas (like Olympic arenas) will be in the clear.

It may sound crazy but it's not new. It has been practiced for more than 60 years. Two scientists, Vincent Schaefer and Bernard Vonnegut, developed cloud seeding methods in 1946. The first attempt was made in November of that year using Schaefer's method. Snow fell near Mount Greylock in Massachusetts that day.

On that day, and many times since then, scientists took to the skies. They distributed chemicals in targeted upper level clouds. The idea was to simulate and accelerate the precipitation process. The chemicals - typically either dry ice or silver iodide - cause ice crystals to grow to the point that they "precipitate out" creating rain (or snow depending on the climate).

This process can be carried out from airplanes or from the ground. Reports said that the Chinese would shoot rockets or other artillery into the sky with canisters targeting the clouds around Beijing. Other scientists use devices, like generators, that will disperse the chemicals into the air currents from below.

WHO PRACTICES CLOUD SEEDING?

Countries around the world have used cloud seeding for various reasons over the years. It's a matter of general interest to many scientists who study weather and precipitation. And, of course, there those scientists like hurricane researchers who attempted to use cloud seeding to reduce the ferocity of hurricanes in the 1960s. Unfortunately, it didn't work. Perhaps they will find a way that cloud seeding research can help deter or predict other phenomena.

Many nations use cloud seeding as a way to deal with drought. Areas in the U.S., including Utah and Nevada, have been known to practice it as a way to bring moisture to their typically dry terrains. They even have state water resource divisions that manage its use in their states.

Outside the U.S., countries like Canada, Australia, Russia, China and others in Southeast Asia have also used cloud seeding to deal with situations that could use a little extra precipitation - drought, dust storms, and pollution to name a few.

Some governments have practiced cloud seeding to sway other sorts of situations in their favor. Cloud seeding is said to have been used over North Vietnam in the late 1960s and early 1970s to prolong the monsoon season and complicate the Vietcong's efforts there. Additionally, some accuse the U.S. of cloud seeding over Woodstock in 1969 in an attempt to wash out the Hippie music fest.

Others have carried out less strategic but far more superficial and/or routine uses of cloud seeding. Russia and China both attempt to keep national holidays (or Olympic venues) clear and dry. Canada keeps its ski slopes in business. And airports around the world consider it for keeping things up and moving in the skies.

SO WHAT'S SO CONTROVERSIAL ABOUT CLOUD SEEDING?

Many scientists feel that cloud seeding is too unpredictable. Part of its failure in subduing hurricanes in the 1960s came because researchers feared their efforts might make hurricanes worse. They just couldn't risk creating a monster storm that might wreak havoc on coastlines.

Hurricanes are a good example of weather conditions with multiple factors in play. When wind, temperature, or other meteorological conditions are accounted for, there is no guarantee that cloud seeding will have the desired effect. It could bring about more precipitation, like a monster storm, it could do absolutely nothing at all, or it could bring less precipitation.

This doesn't go over so well with some scientists or citizens. Especially when if they'd just left well enough alone, there could have been enough natural precipitation to end the drought, quell the dust storm, or wash away the pollution. And then there are the people like those in China who got very upset when the regular use of cloud seeding in some areas let other towns "steal" their rain. Tinkering with nature has always been a controversial exercise - weather is no exception.

Controversy can also surround the unintended consequences of cloud seeding. Chemicals are distributed in the air, after all. That doesn't sound great and in some cases it may not be. Most places don't seed clouds often enough for the chemicals to do any significant damage. However, in areas where "rainmaking" is a more regular practice, levels of silver in the ground are at toxic levels. For now though, this has really done little more than coincide with an increase in algae levels in surrounding waterways. But "toxic" levels of anything don't go over well with the general population.

Other controversies can arise in how cloud seeding is carried out. A recent story out of Russia described how cloud seeding packets of cement were dropped from a plane. These packets contained a silver iodide and liquid nitrogen mixture that would "make rain". When the packet failed to mix and the cement failed to disintegrate, an unhappy Russian man found himself with a big hole in his house. While this sort of thing doesn't happen often, it is always a possibility when things are being dropped from planes or shot into the sky.

Just like the idea of keeping rain away from the Olympics, it all seems a little surreal. It seems a little like playing God, and that is probably the biggest controversy of all. What circumstances really justify interfering with the natural way of things? At what point does playing with weather become playing with fire?

Responsible scientists must weigh these questions, all the potential consequences, and what they hope to accomplish. As long as cloud seeding is around, they will probably all come up with different answers. But with ongoing droughts, pollution, and the need for beautiful nights and days, cloud seeding will continue.

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