Sky Watcher
FEW topics so command attention, particularly in northern environs, as the weather. Each year, it seems, is hotter or colder, wetter or drier, stormier or something else-er than any other. The talk goes on and on - "wretched day!" "at last, the sun!" "will it never rain?" "will it never stop raining?" But, contrary to conventional wisdom, there are those who do something about it. JOSEPH M. BIRD '40, deputy director of the Office of Weather Modification, for one.
After 31 years as an Air Force meteorologist, Bird retired in 1972 with the rank of colonel to join the National Oceanic and Atmospheric Administration of the U.S. Department of Commerce. NOAA's weather modification office monitors operations nationwide and conducts research into more effective means of altering weather to increase precipitation, dissipate fog, suppress hail, and lessen the impact of harmful storms. It also keeps an eye on "inadvertent modification," changes that result from urban "heat islands" and from "all the stuff we throw into the atmosphere," as Bird puts it.
Systematic weather modification goes back to 1947, but weather lore, much of it now scientifically explicable, is deep in every culture. Such legends as rainfall inevitably following battles, Bird suggests, can't be dismissed as old wives' tales, since dispersal of cannon smoke into the air is basically akin to the modern technology-by which clouds are stimulated to release moisture or to the concentration of air-borne pollutants that produce greater rainfall downwind from large cities.
Cloud seeding, he explains, is a.process of injecting into waterbearing clouds particles around which suspended moisture condenses to form drops. In "dynamic seeding" - based on the physical principle that pure water does not freeze at 32 degrees Fahrenheit - particles dispersed into high clouds in effect pollute pure water, causing it to freeze and fall as rain or snow. The seeding agent is most commonly silver iodide; the method of dispersal may be from the ground or from aircraft.
In the absence of a national weather modification policy - legislation to that end has been authorized by Congress - 31 states have laws governing such activities. Although NOAA has no regulatory power, operators are required to submit project plans and detailed reports, including environmental-impact statements. Rain dances and other "ceremonies, rites, and rituals intended to modify the weather" are specifically exempted.
Of the 88 projects reported last year, some were sponsored by states, counties, and community associations concerned usually with enhancing precipitation, others by airlines or airports generally bent on dispersing cold fog, power companies or municipal districts out to increase water resources, or federal agencies engaged almost entirely in research. The great majority occurred in the West, and well over half were at least partially aimed at increasing rain or snowpack.
"That cloud-seeding has resulted in 10 to 15 per cent more precipitation downwind from the target area" than might otherwise have occurred is "strongly indicated," Bird says. Such verbal hedging is necessitated, he explains, by the difficulty of establishing a causal relationship. But preliminary results of the recently completed five-year Florida Area Cumulus Experiment present the same "strong indications" of increases ranging from 20 to 70 per cent. Elaborately controlled dynamic seeding of super-cooled water in rising cloud towers was apparently effective not only in increasing the size and rain production of individual convective clouds, but also in promoting cloud merger and increasing rainfall from groups of clouds over a large target area.
STORMFURY, a project designed to diminish the impact of severe hurricanes by enlarging the diameter of the storm's eye, uses the same technique. When supercooled water just outside the eyewall is seeded, the freezing process releases heat, making the clouds more buoyant. As they rise through convection, they form a new eyewall of greater diameter, thus reducing wind velocities. The analogy. Bird explains, is to the figure skater who picks up speed in a spin by drawing the arms close to the body and slows down by spreading them out. STORMFURY seeded four hurricanes with inconclusive results between 1961 and 1971, when it became relatively inactive. Now, with sophisticated new equipment, the project awaits an eligible hurricane for a full-scale test of improved technology that could substantially reduce the havoc.
The nature of their work makes weather-modification personnel a magnet for all manner of correspondence - anguished pleas to "send rain," angry denunciations for conspiring to prevent it, questions of whether one man's rain is another's drought. "Rain clouds depend on nature," Bird says. "All seeding can do is increase precipitation when the potential is there." He doesn't buy the "robbing-Peter-to-pay-Paul" theory that cloud-seeding in one area reduces rain in another. "Of all the moisture carried in the atmosphere as it comes in over the land from the Pacific Ocean or the Gulf of Mexico, only about three per cent falls before it reaches the Atlantic coast. Most cloud formations are not very efficient rain-producers."
Of fewer than a dozen legal actions over weather modification since 1950, most have claimed flood or hail damage allegedly resulting from cloud-seeding; in all but two or three still pending, the plaintiffs failed to prove cause-and-effect. One suit still before the courts arose from the disastrous 1972 flood in Rapid City, South Dakota. "In that case," Bird says, "the operator was using salt, not very effective since it absorbs water, and the area was not significant." Such a huge storm, he adds, "is already 100 per cent efficient - it dumps everything it's got in it - so there's no way seeding could have increased the rain."
The long-range potential for operations in one part of the globe having catastrophic effect on another led to the signing only last year of an international agreement to outlaw what is commonly called "environmental warfare." The treaty binds the signatory nations - 43, to date - "not to engage in military or any other hostile use of environmental techniques having widespread, long-lasting, or severe effects as a means of destruction, damage, or injury to any other state party."
Bird, who holds a graduate degree in international relations, was a member of the U.S. negotiating team, along with men from the Arms Control and Disarmament Agency, the Department of Defense, and the CIA, that hammered out the specifics with their Russian counterparts at meetings in Moscow and Washington. He found the Russians good hosts and hard-line negotiators, most intractable predictably on the issue of monitoring, but he considers the agreement an important step in keeping the peace.
Weather modification is an imprecise science still in its infancy, Bird points out, but the potential of future technology is incalculable. "There is a theory, for instance," he says, "that heat could be transmitted by radar, thereby changing the thermal atmosphere and hence the jet stream," with devastating effect on climate and food production.
Without international agreement not to indulge in unrestrained use of yet-undiscovered techniques to alter the environment, there might one day be no one left to talk about the weather.
