by: Victor Boesen
The scene was a small laboratory on top of 6,280-foot Mount Washington in New Hampshire during World War II. Vincent John Schaefer was working as research assistant to Dr. lrving Langmuir, associate director of the General Electric Company's research laboratories, on some projects for the government that involved weather research.
From the window young Schaefer watched the west wind continually push moist air up the sides of the mountain. In the colder air of the higher elevation the moisture was con densed into cloud droplets, and for days on end the mountain was wrapped in supercooled clouds.
Schaefer realized that because of the low temperature which prevailed over Mount Washington supercooled clouds must be normal for this latitude and elevation. Therefore, he reasoned, most rain and snow must come from supercooled clouds, the rain starting as snow. But how?
Schaefer had read about Tor Bergeron, the noted No wegian meteorologist, who suspected that if somehow ice crystals got into supercooled clouds from the outside, or were caused to form within the cloud, the moisture in the cloud might freeze on the ice crystals. This would start snowflakes to forming, which would turn into rain in the warmer air below.
Schaefer also knew about the German weather authority, Walter Findeisen, who carried Bergeron's thinking a step further. What caused the ice crystals themselves to form in the first place?
As Findeisen pondered the question, it occurred to him that the ice crystals were created by supercooled moisture freezing on the dust specks in the atmosphere. Findeisen predicted the day when these dust specks, or nuclei, would be provide artificially.
When the war ended, Schaefer and Langmuir set out to learn more about supercooled clouds and the rainmaking processes They needed to reproduce a supercooled cloud of their own in the laboratory, so they could have control and see close- up what they were doing.
Schaefer got hold of one of the deep-freeze boxes which the company manufactured and made it over slightly for these purposes. He lined it with black chiffon and equipped the in- terior with a small, powerful searchlight.
Then, with the temperature in the four-cubic-foot space below freezing, Schaefer breathed into the box several times until the air was saturated with the moisture from his lungs. The box filled with gray fog-his own supercooled cloud.
The next step would be to turn the fog into snow. For weeks he patiently exhaled into the freezer and powdered the fog bound interior with different kinds of fine natural dust, one at a time. He tried scores of things: sea salt, clay, minerals, assorted particles from the atmosphere. Nothing happened.
He tried dropping the temperature of the box slightly- down to four below zero at the bottom of the box and fourteen above at the top. Still nothing happened. (He had no way of knowing, of course, that this was still too warm-that natural nuclei, as we now know, don't become fully effective until the temperature is around thirteen degrees below zero F.)
So it went. Nothing worked. How nature turned the moisture of supercooled clouds into snow and rain remained her secret -it looked as if she meant to keep it.
Then came July 12, 1946. The day was fiercely hot. To help cool the laboratory, Schaefer left the lid off his freezer box, as is done in supermarkets.
When he returned from lunch, he found that the tempera- ture in the box had risen sharply. It was now only a little below freezing at the top. All during his experiments he had wondered what would happen if something extremely cold were introduced into the fog of the supercooled cloud in the box. This seemed a good time to find out.
Schaefer found an eight-inch chunk of dry ice-which is frozen carbon dioxide, with a temperature 109 degrees below zero F.-and thrust this into the cloud. Instantly the beam of the little searchlight in the box filled with ice crystals-trillions of them-shimmering against the dark chiffon background.
As Schaefer watched, spellbound, the tiny crystals quickly formed into snowflakes, growing rapidly larger as they fed on the rest of the moisture in the box. The flakes fell to the bottom in a Tom Thumb snowstorm, covering it.
Schaefer now knew at least one thing. It appeared that at some point far below zero the water droplets in a supercooled cloud flashed into ice crystals on their own without the help of nucleating dust particles. At least this seemed to be what happened in the box.
He repeated the experiment several times using only a pinch of dry ice each time. The results were the same as with the large piece. A snowstorm always followed.
But how cold did it have to be for this to happen? At what point on the thermometer did this spontaneous flash-over of the water droplets into ice crystals take place? This was the next question to settle.
Schaefer and Langmuir froze a pellet of mercury in liquid air, which is close to three hundred degrees below zero Fahren heit, and put this into the cold box. Since mercury melts at minus-thirty-eight degrees F., they knew they had the answer when the melting started and the ice crystals stopped forming at the same time.
The answer was that water droplets change into ice crystals without the benefit of nucleating dust particles when the temperature gets down to about forty below zero F.
At any rate, that was the way it was in the laboratory. I was it the same outside, under nature's own conditions?
Nature was slow to provide the clouds Schaefer and Lang muir needed to find out. The summer passed and it was well into autumn, November 13, before some clouds appeared f looked as if they might be supercooled.
Schaefer flew above the most promising target, a mile-long cloud hanging over Mount Greylock in Massachusetts. He peppered a few pounds of dry ice over the side of the airplane. Langmuir, watching from the ground, saw long streamers snow break from the cloud and fall earthward. There was answer.
What was true in the controlled conditions of the labora tory also seemed to hold true out in the open sky. When was cold enough, liquid droplets of water turned into crystals by themselves without the need of nucleating dust particles.
Once started, the conversion from droplets to ice crystals to snowflakes went fast. Apparently, like water speeding up as it approaches a narrows, pulling other water after it, the space vacated by the droplets as they crowded after the growing snowflakes brought other droplets pushing in behind at accelerating rate.
Schaefer and Langmuir had made a good start on unlocking the clouds, using dry ice. Bernard Vonnegut, another member of General Electric's research staff, wondered if there might not be something better to use than dry ice. Dry ice was bulky, perishable, and inconvenient to handle. Perhaps there was something without these drawbacks which would do the job just as well.
Vonnegut studied the structure of a number of natural crystals, then discovered that the silver iodide particle, a compound of silver and iodine, had almost the identical structure of the ice crystal.
He tried vaporized silver iodide on the fog in Schaefer's laboratory cold box. Sure enough, ice crystals fairly exploded into being, followed by the Lilliputian blizzard.
Silver iodide proved to be very special indeed in its ability to act as a freezing nucleus for ice crystals. Schaefer tested many kinds of natural materials-the smoke from forest fires and from factory stacks, volcanic dust, bits of sea salt, windblown soil. None took effect until the temperature was down to near zero.
The best of the lot was soil dust from North Dakota-the kind that blew away by the millions of tons in the dust storms of the Dirty Thirties. This went to work fairly early, when the temperature was eighteen degrees. But even this was not good enough.
Silver iodide, by contrast, took effect much sooner, when it was as warm at twenty-five to twenty-eight degrees, only a few points below freezing. At fourteen degrees, where other par ticles were just starting to work, silver iodide was in full operation.
Many ways of vaporizing silver iodide were tried. One ex- perimenter, lrving P. Krick of the California Institute of Tech nology, developed a generator consisting of a small firebrick oven inside a steel box about the size of a television set, which has proved to be the most effective. In this one the silver iodide was impregnated in coke and burned at the white heat of 2,500 degrees. Impelled by a fan blowing through the fire, the vapor ized silver iodide rose invisibly from the little furnace and drifted off toward the clouds on the rising air currents, feeding the clouds at the rate of billions of particles a second.
As the silver iodide rose, it also dispersed widely. This was another advantage over dry ice. By the time it arrived at seeding levels, perhaps fifty miles from where it started, then particles could be spread throughout thousands of cubic mile of the atmosphere.
Silver iodide particles are inconceivablv small. Vincent Schaefer has estimated that if each of the two hundred million people living in the United States-every man, woman, and child-were given 10,000 silver iodide particles, and then each dropped his 10,000 into a common pile, it would make a heap the size of a grain of salt.
Now that the scientific basis of rainmaking at last had been found, there were soon lots of rainmakers in the field--not all unfortunately, as qualified as Vincent Schaefer. Ranchers wanted rain for their pastures and rangelands. Farmers wanted rain for the crops. Power companies wanted more water in the streams to turn their generators. Cities needed reservoirs filled. Mountain resorts could use more snow for the ski slopes.
It was a seller's market for the rainmakers.
They made contracts to bring rain to millions of parched acres charging a half to one cent an acre, for pasture, up to fifteen cents an acre for crop land. Some worked on a contin gency basis-no rain, no pay. Some operated with a few buckets of dry ice, heaved from an airplane. Many farmers and ranchers did the job themselves, passing up the professionals.
Less than a half dozen years after Vincent Schaefer thrust the piece of dry ice into his coldbox, finding the key to cloud seeding, eager rainmakers had seeded over one fourth of the United States. Rainmaking was going on throughout the world.
How much rain the rainmakers were making was a matter of argument. There were a good many dissatisfied customers To many people, this was simply more of the old witchcraft. The controversy split pretty much on a line between those who had obtained rain and those who had not.
The scientists were as divided as the rest. Some argued that cloud-seeding for rain made sound scientific sense. Others including top men in the United States Weather Bureau, insisted that the idea was nonsense.
To learn the truth, Senator Francis Case of South Dakota, who himself was involved in rainmaking experiments, introduced a bill in Congress providing for a President's Advisory Committee on Weather Control. President Eisenhower signed the bill into law on August 9, 1953 and on December 9 named the committee members. They included five from the Presi- dent's cabinet, along with the director of the National Science Foundation and five members of high standing in the fields of science, business, and agriculture.
The committee was headed by Captain Harold T. Orville who had been the Navy's chief weatherman during World War II and charted the weather for General James Doolittle's historic raid on Tokyo early in the war.
The job of the President's Advisory Committee on Weather Control, as Captain Orville spelled it out, was to "study and evaluate public and private experiments designed to modify the weather"-that is, make it rain. Everybody engaged cloud-seeding, whether for hire or as a scientist experimenting, was required to keep the committee posted on what he was doing.
"If the Advisory Committee finds that weather modification experiments cannot produce important results," Senator Case said, "it will so report and thus deter farmers and ranchers from spending their money unwisely."
The committee went at its work carefully. The members spent the first six months studying the subject of rainmaking meeting with scientists and making trips into the field. They even borrowed some silver iodide generators and tried some seeding tests of their own.
Four years later, December 31, 1957, the President's Ad- visory Committee on Weather Control reported its findings. Seeding the clouds for more rain did indeed work. Overall, seeding had boosted rainfall by nine to seventeen percent.
This increase was a great deal more than needed to be worthwhile. It takes only a little more rain to make a big dif erence in the size of the crop. A study by Dean A. M. Eberle of the School of Agriculture at South Dakota State College and vice-chairman of the President's committee, showed that just one percent more rain during the growing season paid the cost of the seeding at harvest time.
The National Academy of Sciences, however, was skeptical. Made up of the nation's leading scientists, NAS was founded in 1863, during the Civil War, as official adviser to the govern ment in all matters of science and technology. Ever since then it has been in the forefront of scientific development. Its coun sel led to the founding of many key public institutions, such as the United States Weather Bureau, the National Bureau of Standards, and the United States Forest Service.
NAS felt that the work of the rainmakers ought to be studied some more, and it named a panel to do so. For a half dozen years the panel pored over the steadily mounting mass of information on cloud-seeding, then it agreed that this was in fact an effective way to improve rainfall. Moreover, it raised the claims of the President's Advisory Committee by a few points, saying that seeding increased the rain by ten to twenty percent rather than nine to seventeen percent.
Also, the findings of the NAS panel were upheld by scien tists of the Rand Corporation, one of the nation's better known "think tanks," in Santa Monica, California. And-a special feather in the cap of the cloud-seeders-the weather bureau finally agreed there was something to be said for seeding.
The rainmaker at last had earned his credentials.
Meanwhile, ideas were developing to give the rainmaker more to do than just make it rain. The President's Advisory Committee had been excited by the promise of cloud-seeding and in its 1957 report had urged that researches be continued on a greatly expanded scale.
Perhaps cloud-seeding might be used as a weapon against storms, as well as against the old enemy, drought.
For example, the committee emphasized the problems of hail. In seconds hail often undid the good work accomplished by the rain from the same clouds, flattening the farmer's crop and destroying his work for the year. Hail is, of course frozen raindrops. Possibly if the cloud threatening hail were seeded soon enough, it could be turned to snow, preventing hail. This had seemed to work in at least one area, the committee learned. Look into this some more, it urged.
And what about lightning? The President's Advisory Com mittee spoke of this too. Lightning ran far ahead of careless campers as a cause of forest fires in the west. The conditions that produced hail were often the same as those that brought lightning. Therefore, possibly the same methods that stopped hail might also stop lightning. All at once man's ancient dream of asserting some authority over the elements was not so fanciful. If the views of many of the nation's leading scientists were accepted, Captain Orville said, the answer to the question was yes-control of the weather was possible.
There could hardly be a more momentous prospect. In the United States alone, storms cost 1,200 lives and $11 billion an- nually on the average, to say nothing of what it cost not to get enough rain.
In silver iodide it appeared man had found the key at least to temper these adversities. But before he could use the key effectively, he must first know in advance what the weather was going to do; he must be able to forecast it. This, in turn, called for knowing more about how the weather operated. For all his studying and pondering through the ages, he still knew very little about that.
Controlling the weather remained a complex problem which for every answer always seemed to raise more questions. Man was yet only at the beginning of what he needed to know.