Storms Above the Desert


Tampering With The Weather


While Workman was reluctantly becoming a college president, scientists in a corporate laboratory half a continent away were preparing to modify the weather.

Before July 1946, the famous observation that "everybody talks about the weather, but nobody does anything about it" might as well have been a law of physics. Weather modification belonged in the realm of hokum until that July. Then, without warning or expectation, chance favored the prepared mind of a General Electric Laboratories scientist named Vincent Schaefer, and cloud seeding was born.

Although Schaefer's discovery was sudden and serendipitous, much of the research behind it had been going on at GE since 1940. In that year, Schaefer's boss, Dr. Irving Langmuir, was approached by the U. S. Chemical Warfare Service to study the filtration processes used in gas masks. That entailed generating various kinds of smoke and studying their properties on the particle level. Langmuir, a Nobel laureate and, by all accounts, one of GE's resident geniuses, had in Schaefer a hard-working associate who contributed greatly to the research. (Schaefer started his GE career as a machinist; after working with Dr. Langmuir, he came to be a respected scientist in his own right.)

Langmuir and Schaefer continued with this and other aerosol-related war research until 1943, when they began investigating the properties of supercooled clouds as part of a study of precipitation static. This led them into the problem of aircraft icing, which was especially timely; large numbers of aircraft were flying in icing conditions on missions that could not be delayed or aborted because of bad weather. They studied the problem on Mount Washington, New Hampshire, which experiences some of the worst winter weather in the world.

Irving Langmuir 
with camera

Irving Langmuir with camera.
New Mexico Tech Archives.

When he was not shivering atop Mount Washington, Langmuir made extensive calculations describing ice accumulation on various geometric shapes and materials. Combining these theoretical results with field observations, the researchers incidentally obtained a good working knowledge of cloud structures and the growth of cloud particles. Their work led them to study exactly what happens when water freezes. Schaefer needed to produce cloud-like conditions in the lab instead of seeking them in winter on a frozen, windswept mountaintop, so in 1946 he invented the "cold box," a home freezer--GE, of course-- with a black velvet lining and a viewing light.

By breathing into the cold box, he could produce a little cloud of water droplets that condensed from his breath. Like those in the higher reaches of a cloud, these droplets were supercooled--below the freezing point, but still liquid. Being able to recreate these cloud-like conditions in the lab was a major practical step in cloud investigations. GE's public relations people were almost as proud of it as he was (although they were exasperated by reporters who insisted on calling his freezer a Frigidaire.) In spite of the nomenclature dispute, this elegantly simple piece of equipment became a cornerstone of cloud research.

On July 13, 1946, Schaefer came to work and found that his cold box, usually kept at minus twenty-three degrees Celsius, had been turned off. Eager to recool it in a hurry, he went down the hall and got some dry ice. When he put the dry ice into the cold box, an abundance of ice crystals suddenly appeared in the fog. He experimented further and found that even a tiny grain of dry ice would produce this effect. (Later research showed that any substance with a temperature of minus forty degrees Celsius or below would do the job.)

Langmuir, who had been in California when Schaefer made the discovery, followed up with a theoretical study of the growth rate of ice nuclei produced by dry ice, calculating the velocity, fall time, and dissipation rate of the ice particles. When he saw how difficult and time-consuming this would be, he sought and found a junior member for the research team.

The man he found was Dr. Bernard Vonnegut, then in his first year with GE. He, too, had spent some of the war years studying airplane icing and had also worked on smoke filtration. His graduate work in physical chemistry had concerned the freezing points of very dilute aqueous solutions of various chemicals. As Vonnegut worked on the calculations with Langmuir, he realized that it might be possible to cause ice crystals to form in the cold box around particles whose crystal structure was similar to that of ice. These "ice nuclei," he hypothesized, might provide a kind of pattern or template on which water molecules would deposit themselves in the ice crystal arrangement.

Kiale Maynard a GE Lab technician

Kiale Maynard, a G.E. Labs technician. New Mexico Tech Archives.

The obvious next step was a systematic search for such nuclei. It was, at that time, a purely scientific investigation rather than a deliberate attempt to develop a new technique. After contemplating the crystal structures of more than a thousand substances, Vonnegut concluded that antimony metal and the iodides of lead and silver were the best candidates. At first, experimenting with various forms of these substances, he achieved little success--probably because (as he found out later) his bottle of silver iodide was heavily contaminated with sodium nitrate, a fairly good antifreeze. But on November 14, 1946, he introduced a smoke made of silver iodide particles into Schaefer's cold box and observed a spectacular fallout of ice crystals.

In the meantime, Schaefer had become the first person to seed a cloud. On November 13, Schaefer and pilot Curtis Talbot successfully used dry ice to induce precipitation in a cloud--"an unsuspecting cloud over the Adirondacks," as Schaefer put it in a technical report. Having caught the four-mile-long cloud unawares, he and Talbot proceeded to plow a trough along its top with particles of dry ice. Snow began to fall from the cloudbase. Although the snow melted and evaporated before it hit the ground, The results were dramatic enough to change cloud seeding from a laboratory curiosity into a practical technique.

The GE group made several successful flights that winter, proving that dry ice seeding did induce precipitation under certain conditions. But the project soon outgrew them; a full-scale cloud seeding program would require personnel, aircraft, and other resources that the lab did not have. Some far-sighted individuals in GE's legal department also pointed out the modifying the weather could involve the company in a great deal of trouble.

In February 1947 the Army Signal Corps, the Office of Naval Research, and the Air Force came to the rescue with aircraft and support for the seeding efforts. Schaefer dubbed the operation "Project Cirrus" because its goal would be to transform supercooled water droplets into ice crystals, the stuff of cirrus clouds.

Given the goals of the project, it was natural for the researchers to go to New Mexico. Although a substantial part of Project Cirrus, including the official headquarters, remained in the Northeast, the most rewarding results were obtained in New Mexico. Hundreds of clouds in the Albuquerque and Socorro areas were seeded during the course of the project.

The GE researchers, who came to New Mexico in 1948, were lured by the radars, cameras, and expertise of the R&DD, but they were attracted most of all by the unique thunderstorms of the region. During the summer months in central New Mexico, almost every day dawns with a clear blue sky. But by 10 or 11 A.M., puffs of cumulus clouds begin to appear over the mountains. By early afternoon on a good day the solid white mass of a cumulus cloud casts a shadow on the mountaintop. With the right amount of water vapor in the air, the correct degree of solar heating, and a bit of luck, the cumulus cloud continues to develop into a full-fledged thunderstorm. (Ironically, one of the advantages of the area is that the first two conditions are marginal. If there were much more water vapor and heating, the storms would grow too big too quickly for convenient study.)

Irving Langmuir and 
Bernard Vonnegut

Irving Langmuir (left) and Bernard Vonnegut on the desert near Socorro. Photograph courtesy of Charlie Moore.

Thunderstorms can develop in two ways. The giant ones that deliver torrential rains, large hail, and an occasional tornado are usually frontal storms. They arise when two large air masses of different temperatures collide, and they move with the fronts that gave them birth. Under some circumstances, all the storms along a front can turn into a mesoscale convective system, a kind of giant thunderstorm composed of many clouds. These storm systems, only recently recognized for what they are, cause more damage than any weather phenomenon short of the hurricane--which itself is a system of thunderstorms.

The scientists who study these big storms have to mount their equipment on trucks and chase the clouds down the highway. Those conditions are fine for studying the outward aspects of a storm, but they place severe limitations on the examination of its inner workings. Studying frontal storms has been likened to looking into a washing machine during the spin cycle and trying to figure out what articles of clothing are inside.

While the big frontal storms are spectacular and fascinating to study, they have never really been the business of researchers in New Mexico. The scientists there are interested in orographic air-mass storms, which arise over uplifted terrain because of solar heating. Although these storms get plenty of respect from the people below, as thunderstorms go they are rather puny. A typical one might reach 30,000 feet, and is generally the only storm for several miles around. These clouds are not only small and isolated, but also relatively stationary. With no large-scale winds to blow them around, they tend to move only a few miles during their lifetimes. This made them ideal for Project Cirrus, just as it makes them ideal for the kind of studies carried out today at Langmuir Lab.

The convection processes that build the classic New Mexico thunderstorm get their start in midmorning as the sun heats the local terrain. As the air within a meter or so of the ground gets warmer, it also becomes thinner and begins rising. In a process known as orographic lift, the terrain acts as a guide for the rising air. Parcels of warm air balloon up the slope until they reach the peak, where they begin to rise vertically.

Developing cumulus cloud

An anvil cloud

A midmorning cumulus cloud becomes a rainstorm and finally an anvil cloud in central New Mexico.
Marvin Wilkening photographs.

The rise of the parcels of warm air creates turbulence in the surrounding air by displacing the cooler, denser air above. The cool air has nowhere to go but down. Soon the warm, humid updrafts are surrounded by downdrafts of cooler air.

Relative humidity--the ratio of the amount of water vapor in a parcel to the greatest amount it could hold at that temperature--then comes into play. When the relative humidity is approximately 100 percent, the parcel is saturated and can hold no more water vapor. The temperature at which this occurs is known as the dew point.

As the parcel rises, its constant expansion helps it become saturated. Since gases cool as they expand, the parcel is constantly approaching the dew point. Non-saturated air cools at about ten degrees Celsius for every kilometer that it rises. Sooner or later the dew point is reached, and the water vapor can no longer remain a gas.

But the excess water vapor is still there, and once saturation occurs it begins to condense onto tiny particles in the atmosphere. These particles, called condensation nuclei, may be solid--dust, for instance--or liquid. When large numbers of the resulting cloud droplets are distributed throughout the parcel, they scatter enough light to become visible. (Even the most ominous-looking cloud is mostly composed of air; the water vapor and ice particles may weigh a million tons, but account for only a few millionths of the cloud's volume. By human standards, a cloud is much more of an optical phenomenon than a material thing.)

Once the air has become saturated, the rate of cooling as it rises becomes slower, for a reason grounded in the basic difference between a gas and a liquid. A gas, such as water vapor, has more thermal energy in it than a liquid. Thus, when the water vapor condenses, the excess energy has to go somewhere; it ends up heating the nearby air. This heating partially compensates for the cooling caused by the expansion. The parcel of air, still rising, is now cooling at only six degrees per kilometer, a figure typical of New Mexico clouds.

That figure, known as the moist adiabatic lapse rate, is the key to the growth of a cloud. The parcel of air, now far from the original heat source on the sunny ground, is cooling off. But the dry air through which it is moving is still getting colder at the dry adiabatic lapse rate of ten degrees per kilometer. The net result is that the cloud is still warmer and less dense than the surrounding air, so it continues to rise.

The rise and fall of neighboring air parcels causes turbulence, so that the warm, moist air and the cool, dry air mix, lowering the amount of water vapor per cubic meter. In addition, rising parcels sometimes rise too high, whereupon they sink and their water droplets evaporate. These two factors can combine to make the morning's first clouds literally disappear into thin air.

Sometimes, though, a convective system of rising air grows large enough to withstand a little mixing and evaporation. If there is enough moisture in the air, a fair-weather cumulus cloud forms. Cumulus clouds, the familiar cauliflower clouds of summer, look simple and peaceful from the ground, but a flight around one reveals billowing white masses boiling upwards on a scale that dwarfs the airplane. Each cumulus cloud is made up of many parcels of air, some on the rise, others on the way down. This continuous rise and fall of air parcels gives the cloud its characteristic billowing top. The cloudbase remains flat, marking the height at which condensation first takes place.

Even as scientists crane their necks hopefully at the cloud, many things can stunt its growth. A severe wind shear, a radical difference in direction between strong winds aloft, can limit the cloud's growth. Even worse is a temperature inversion, which means a stable air layer that the cloud turrets may not be able to poke through. And there simply may not be enough heat and moisture involved to support a big storm.

But if the conditions are right, one of these cumulus clouds, peaceful, rainless, and un-electrified, keeps on developing. Bigger and more vigorous than its neighbors, able to control the convective scene over many square miles, it grows in size and complexity: a cumulus congestus, dominating its region of the sky.

Within the cumulus congestus, several processes are happening at once. The cloud droplets collide with one another. Some of them bounce away, but others carry minute, opposing electric charges that help them coalesce, forming bigger droplets. As these droplets grow, some of them become involved in a tug of war between the updrafts and the force of gravity. As the droplets collide and coalesce, they become drizzle drops, and gravity begins to win the contest. The big drops fall, picking up any smaller cloud particles they happen to run into. Radars begin to show a precipitation echo within the cloud as rain begins to fall.

If the cloud keeps growing, it can develop into a cumulonimbus, a big, highly convective thundercloud. At this point, it becomes electrified, a process that still causes scientific controversy. But Langmuir and company were not primarily interested in thunderclouds in the late forties. They wanted clouds for rainmaking.

The Project Cirrus team arrived in New Mexico in October 1948, having been warned that the rainy season was already over. A popular local aphorism holds that anyone who tries to predict the weather in New Mexico is either a fool or a newcomer. Their arrival was greeted by rains. Torrential rains, causing flash floods down the arroyos. The anomalous weather was a bit embarassing for the R&DD staff, but it certainly demonstrated the area's potential as a site for atmospheric research.

Although the rain was a good omen, it wasn't a necessary condition for Project Cirrus. Cloud seeding works by causing minute ice crystals to form inside a supercooled cloud; it does not matter whether it is warm enough below for the falling crystals to melt.

Anvil cloud over Magdalenas

An anvil cloud over the Magdalenas, August 14, 1962.
Charles Treseder photograph.

Journalists in parched New Mexico were enthused about Project Cirrus. They quoted Mark Twain, as reporters are apt to do, then triumphantly refuted him. Finally somebody had done something about the weather! Some of the people who wrote about cloud seeding were well informed and cared about the scientific accuracy of their reportage. Balancing those conscientious individuals was the Albuquerque journalist who wrote that Langmuir had gone up in a B-17 and made a cloud disappear and that area residents should not be alarmed at the sight of oddly-shaped clouds.

Workman and Reynolds found themselves in the midst of all this weather modification activity, they were distracted from their thunderstorm and lightning research. There remained a research effort called the Thunderstorm Project, complete with a Thunderstorm Laboratory at the School of Mines, but the days of sitting in a field and watching a distant thunderstorm were far from their minds.

One day, Reynolds was in a B-17, flying around the mountains near Albuquerque in search of an appropriate cloud. "Drop the ice," he ordered when one was found. They dropped the ice--all in one solid 50-pound chunk. The experiment involved water ice, not dry ice, and the shaved material had frozen together in the flight through the high, cold air. Fortunately, they were over an unpopulated area in the high desert southeast of Albuquerque. But they were also near Kirtland Air Force Base, and someone had neglected to inform them about the bomber. Unbeknownst to Reynolds, a fighter had been scrambled to inspect the mysterious aircraft. The fighter was flying behind and below the B-17 when the ice was dropped. For once in aviation history, Murphy's Law did not apply. Some red faces were in evidence, but both the fighter and the careers of the B-17 crew escaped damage.

Despite such aerial misadventures, the cloud-seeding project was far more than a series of "let's try this and see what happens" experiments. As Project Cirrus grew, so did its scientific sophistication. Specialized apparatus was developed, including an automatic cloud-type identifier and an array of devices to control the sizes of the seeding particles. Planes laden with instruments flew in and around the seeded clouds so that scientists could tell exactly where the seeding materials were going and what effect they were having.

Workman's silver
		iodide smoker
Project Cirrus B-17 bomber w/ modifications

Workman's mobile silver iodide smoker in operation. New Mexico Tech Archives.

A Project Cirrus B-17 bomber with some optional equipment. New Mexico Tech Archives.

The idea of making rain, however, was certainly not the invention of Langmuir and Schaefer; what stereotypes the American Indian if not the rain dance? The celebrated rain-makers of the American West went the Indians one better, firing cannons and skyrockets to give drought-stricken sod-busters a good show for their money. During World War II, a Luftwaffe pilot even dropped 300 pounds of sand into a cloud over Yugoslavia, perhaps in a misguided attempt to provide condensation nuclei. But the days of shamans, confidence men, and earnest dilettantes had given way to the day of the scientist. Never mind whether Project Cirrus was going to help bring rain to New Mexico, the scientists were sure that the knowledge to be gained in the attempt would be a good return on the investment.

They experimented with silver iodide as well as dry ice. That was a more peaceful pursuit than dry-ice seeding, because silver iodide could be vaporized on the ground and borne up by the updrafts of a promising thundercloud. To mobilize the research, a 1948 Oldsmobile coupe was equipped with a flamethrower-like silver iodide smoker.

Seeding from ground level was nothing new; on an expedition to a Navajo village, Workman and Reynolds found that the Indians had been doing it since time immemorial. First, the scientists demonstrated nucleation with a portable cold box. Unimpressed, the Indians responded by burning the charred bark of a tree that had been hit by lightning. The scientists were using applied physics, while the Indians were using sympathetic magic, hoping that like would bring like. Both have claimed success.

The silver iodide seeding efforts eventually sparked a major disagreement between Langmuir and some of his colleagues. Langmuir, who was back in Schenectady, New York, at the project headquarters, had some R&DD people do a silver iodide experiment for him in Socorro. Beginning in late 1949, he had them seed the local clouds eight hours a day, three days a week. Langmuir eventually noticed a pattern. Several days after clouds were seeded in Socorro, it would rain in the Ohio Valley.

Come Thanksgiving 1951, the R&DD employees asked for a few days off, and Reynolds agreed. Langmuir was furious. Where was their dedication? But his temper cooled down when he checked the weather reports. Sure enough, a few days after they stopped seeding in Socorro, the expected rainstorm Ohio Valley failed to occur.

Langmuir came to the conclusion that his seeding project in Socorro was causing the Ohio Valley rains. It was a daring step, because researchers learn early that correlation alone does not imply causation. But to Langmuir, the pattern was stretching the bounds of coincidence.

Whether true or not, it was a disturbing conclusion. If local activity in the New Mexico desert was causing rain by the banks of the Ohio, something was going on that could not be explained. Langmuir arrived at the tentative conclusion that some type of resonance in the atmosphere was at work, that the seeding in Socorro was doing something to the atmosphere rather like striking a tuning fork. Such long-period resonances were known to exist, but little else was known about them.

Langmuir finally decided to present his results at a conference. His colleagues tried to dissuade him, reminding him of the local nature of the research effort and the great distance between Socorro and Ohio. Finally they simply told him that he was talking nonsense. He presented his results anyway.

Inside an instrument trailer
Outside an instrument trailer
Inside and (right) outside an instrument trailer, circa 1957.
New Mexico Tech Archives.

No one laughed out loud at the idea--after all, Langmuir was the patriarch of the entire field, and the weather pattern existed--but the break between Langmuir and the R&DD scientists had been made. By the late1950s, cloud seeding had gone completely out of favor in New Mexico. Workman had become a nonbeliever, and to a certain extent so had Reynolds. But Langmuir remained a believer until his death in 1957.

Does cloud seeding work? There is no doubt that introducing dry ice or silver iodide into a supercooled cloud in the proper way causes widespread nucleation and ice crystal formation. Plenty of hard physical evidence verifies that phenomenon. There is also good reason to suspect that Project Cirrus brought down hundreds of millions of tons of rain in New Mexico that would not have fallen naturally. The spreading disenchantment with rainmaking was caused not by doubts about its effectiveness so much as by questions about its predictability and ethicality.

A 1978 case involving the Adolph Coors Company, a Western beermaker, provides a sterling example. The farmers around Alamosa, Colorado, where barley was raised for Coors and other customers, demanded and received a hearing before a special master. They claimed that the company was deliberately overseeding the clouds to prevent rain from falling on Coors barley at harvest time. This, of course, also kept it from raining on neighborhood farms. Coors claimed that they were merely trying to suppress hail. Charles Moore, professor of atmospheric physics at New Mexico Tech, was called in to testify. He testified that the hail-suppression claim was indefensible, and that overseeding a cloud to the extent required by Coors could indeed cause the formation of too many ice crystals too small to reach the ground, thus suppressing rainfall. This view was accepted by the special master, who ruled against the cloud-seeding operation.

The special master's view was apparently also accepted by the Soviet Union. There have been reports of cloud seeding upwind of the Chernobyl reactor site during cleanup operations there. The goal, evidently, was to suppress rainfall that might wash radioactive contaminants into the soil and streams.

In October 1947, Langmuir himself was involved in an episode much bigger and more controversial than the Coors case. He had come up with the idea that scientists might be able to defuse a hurricane by overseeding it and thus disrupting the dynamics of the individual thunderclouds in the storm. Out went his team to penetrate and overseed a hurricane that was off the Florida coast and heading for Bermuda.

Something may have happened; that was the only firm conclusion that could be drawn. The newly seeded hurricane, which had been spending its fury on the empty Atlantic Ocean northeast of Jacksonville, quickly gained strength, made a 90-degree left turn, and roared ashore near Savannah, Georgia. A Miami journalist described the seeding as "a low Yankee trick." Langmuir was thoroughly pleased with himself, but GE's long-ulcerating lawyers were not pleased with Langmuir. The company immediately told their Nobel laureate not to boast about his achievement before the statute of limitations ran out.

But what did the low Yankee trick really accomplish? No one knows, and perhaps no one will ever know. A hurricane, essentially a vicious circle of thunderstorms moving as a collective entity, is one of the most freakish of natural phenomena. Perhaps the seeding gave the hurricane its new strength and steered it back towards land. Then again, perhaps the storm was going to make a 90-degree left turn anyway (hurricanes have performed maneuvers much more radical than that) and the seeding kept it from being even more powerful than it was. And perhaps the seeding had no effect on its course at all.

In any case, cloud seeding was bound to result in a great deal of disappointment, simply because public expectations were so high. A 1949 newspaper piece entitled "R&DD Technicians Saddle Thunderstorms" read, "Perhaps some day the weather man will be able to literally order the weather for the day." Both scientists and the public have learned since then. One of the best markets for the latest and fastest supercomputers is in numerical modeling of the weather. The variables involved are forbiddingly numerous, and no one really knows where to draw the line. The data pour in constantly from satellites, from ships at sea, from ground stations the world over. How much is useful information and how much is noise? Does the course of a butterfly's flight in Peking affect the weather in Hoboken a week later? Some scientists have suggested that it might. Today only the most sensational of the tabloids at the checkout stand would dare to predict the custom-ordering of the day's weather. How could we control the weather without first understanding it fully--and more importantly, how would we dare? The hubris of the Fifties has given way in the Eighties to chaos theory and to numerical modeling.

But, as Reynolds recalls, those were happy days to be a scientist--the days of the postwar technological miracle and the autogyro in every garage. All eyes were on the glory of the scientific future in a jet-propelled America that had split the very atom. Surely scientists could learn to control the weather!

Reynolds, who left Tech in 1955, witnessed Langmuir's tenure as a true believer in rainmaking, and he watched as Workman's enchantment flowered and died. For the past thirty years, he has been the State Engineer of New Mexico, the official in charge of water resources: a man of strong political influence who is known to look unfavorably upon tampering with the clouds. Nobody does much cloud seeding in New Mexico anymore.

Table of Contents

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