Storms Above the Desert

Although E. J. Workman neglected thunderstorm research during his fling with rainmaking, a few diehard atmospheric electricians at the School of Mines continued to probe the inner workings of the thunderstorm. Among them were Steve Reynolds and, later, one of Workman's former students, Marx Brook.

Today, Brook could be called an elder statesman of atmospheric physics, but that honorific belies his tendency to carry on verbal battles with his colleagues through the halls and into the elevator--in a Brooklyn accent that leaves no irony unturned, and often at paint-flaking volume.

Since 1978 Brook has been the director of the R&DD , a senior administrator with little time for active research. But he remains a professor of physics and a mentor to graduate students, reigning over the R&DD as a benevolent tyrant. The spirit of Workman still walks the halls of New Mexico Tech.

In 1954, when Brook joined the Thunderstorm Project, Workman was alive and well and preoccupied with introducing foreign substances into cold clouds. Brook was no stranger to the work, having earned his bachelor's degree at UNM under Workman and Holzer during World War II. After graduation, he had stayed on until 1946, working both on charge separation in thunderclouds and on proximity fuses.

After the war came a four-year sojourn at the University of California at Los Angeles, where he earned his master's and doctoral degrees in physics. At UCLA he studied various properties of nitrogen gas and published three papers on the subject in the Physical Review. Soon, he found his interests turning back toward lightning research, so he asked his old professor for a job.

Brook came to New Mexico Tech with the idea that he was going to be strictly a researcher. But such aspirations are more commonly stated than fulfilled, especially at small colleges; within a year, Workman asked him to teach a few classes. Brook soon found himself to be an assistant professor of physics and has been a member of the teaching faculty ever since.

With senior researchers busy wafting silver iodide into the bottoms of clouds and dropping dry ice onto their tops, Brook found an opportunity. It lay on the Plains of San Agustin, an ancient dry lakebed west of the Magdalena Mountains. Today, the Plains of San Agustin are an important center of research, for the National Radio Astronomy Observatory's Very Large Array radiotelescope is located there. But Brook and a few other physicists from Socorro beat the astronomers there by thirty years.

In 1952, Reynolds and a colleague had set up a small network of "field mills" on the plains. Although the term encourages thoughts of windmills and grindstones, field mills are actually small rotary instruments--think of a coffee can with a small fan inside--that measure the electric field caused by charged clouds. By burying the field mills so their business ends were flush with the ground, the researchers could gather data on the charging of the clouds overhead. Using several field mills allowed them to figure out, by triangulation, how the field strength varied with position and distance from the storm. It was not an exact determination. A single field mill cannot tell the difference between a charged thundercloud a kilometer overhead and a technician rubbing a piece of Teflon a meter away. But two field mills do a fair job, and several of them spread out over a wide area give a good approximation.

Also on the plains were time-lapse cameras that could record the progress of the storms. But one of the most promising new tools the scientists used was radar. The wartime need to detect enemy planes had provided a windfall for atmospheric physics. At last scientists could see through clouds, picking up rain shafts, hail, layers of ice crystals, and other things that had to be located and measured.

The project was soon removed from the plains. Working there had not been without its hazards. Brook once found a rattlesnake curled up inside an instrument package. Reynolds went into a bar in the town of Datil, made an innocent remark to a rancher about the progress of a private rainmaking project, and got punched in the nose. But the real reason for the move was that the plains were not quite the right place for all this equipment and excitement; storms were not frequent enough and were too likely to travel.

By the time Brook arrived, the work was shifting to Mount Withington, at the southeast end of the plains, where small local storms occurred almost daily during the rainy season. One of Brook's early tasks was to help set up a radar on the mountain in an attempt to correlate the first radar echo in a storm with the first detectable electric field beneath it. A good correlation would be a rather broad hint--although not an ironclad proof--that whatever reflected the radar was also generating or gathering charge.

Obtaining a correlation between a radar echo and initial electrification took quite a while. Gathering data in atmospheric physics always does. The electronic equipment often has to be built by the scientists themselves; it is notoriously temperamental, and learning to use it efficiently takes time. Nature is, if not deliberately uncooperative, at least monumentally indifferent. A bone-dry week will end with a flash-flood warning, generally on the researchers' day off. There is no instrument an insect cannot crawl into and no cable a determined rat cannot gnaw through. Rarely will a field operation yield useful data before the third year; sometimes four or five years of frustration are in order.

Steve Reynolds (in cowboy hat) and E. J. Workman (in checkered shirt) prepare balloon-borne instrument package for launch.

Brook and Reynolds were lucky. They had results to present at a conference in 1956. Yes, the radar showed something in there at the same time that we recorded a foul-weather electric field on the ground. No, we didn't fly through the cloud and investigate firsthand, although we would have liked to. Of course, we need more money to continue this research, Back they went to pursue their work further.

By the time they returned, another pair of researchers had become active on Mount Withington. Bernard Vonnegut had left GE Labs to join the Arthur D. Little Company, a scientific think tank in Cambridge, Massachusetts. There he met Charles Moore, another scientist interested in atmospheric research.

Charlie Moore was among the last of a dying breed. Today, the Ph. D. is a researcher's basic union card. Moore had only a bachelor's degree in chemical engineering from the Georgia Institute of Technology in Atlanta. His qualifications for investigating the fundamental theories of atmospheric electricity were largely nonacademic. Armed with neither dissertation nor multiple sheepskins, he made do with peripatetic curiosity, an astonishing amount of energy, and the ability to keep smiling through the barrage of chemical engineer jokes that flew about him every time he picked up a pipe wrench.

Moore also had a singular past. He had done graduate level work in the Army Air Corps during World War II en route to becoming chief weather equipment officer for the China-Burma-India theater. After the war he went to work for General Mills, which had branched out from the cereal business into the balloon business. Moore was the pilot in the first flight test of a manned plastic balloon. He took the balloon up to 10,000 feet, attached to it by his parachute harness. He had several patents to his name and was one of the co-discoverers of traces of water vapor in the atmosphere of Venus--a discovery made from a balloon gondola.

Vonnegut and Moore made something of an odd couple. Moore is garrulous and energetic, with high-voltage blue eyes and a nonstop train of thought. Vonnegut is given to long thoughts and thousand-yard stares. But they had scientific problems in common, and soon they shared a field project. They first went to Mount Withington in the summer of 1956.

They went there in part because Vonnegut had made himself one of the most celebrated heretics in atmospheric physics. Vonnegut had a new and highly unpopular hypothesis of cloud electrification, and his investigations of it had outgrown the laboratory. A whole cloud was needed, and he knew from experience that Mount Withington was the place to find one. Moore came along to, add his meteorological expertise to Vonnegut's knowledge of physics.

Many suggestions have been made to explain how a cloud might become electrified. Most of them have been shown to be wrong for various reasons. Any new hypothesis has to account for the fact that thunderstorms are almost always negatively charged on the bottom and positively charged on top. The electrification scheme presented by a new hypothesis has to involve physically plausible processes and must cause potential differences large enough to result in lightning. A good hypothesis should also be useful in explaining how thunderstorms help maintain the electrical budget of the earth, which is negatively charged and has been for as far back as anyone can tell.

The question of how a quiet cumulus cloud becomes a giant electrical battery has perplexed scientists for a century or more. Lord Kelvin, the great English physicist, decided in 1860 that falling rain somehow charges the cloud. Although Kelvin had no real data behind his hypothesis, it was plausible and carried credence because of his reputation as one of the scientific giants of the century. His hypothesis was handed down through the years, occasionally refined and expanded, until it became one of the basic assumptions from which atmospheric physicists worked.

But Kelvin's hypothesis merely explained how electric charges of different polarities could become separated within a cloud. It gave no clue to where the charge came from in the first place. That was explained by various other means. One of the more popular explanations was the Workman-Reynolds effect. Workman and Reynolds had found that a potential difference existed at the border between an ice crystal and the water that was freezing onto it. They proposed that when water and ice met in a cloud, some of the water, with its negative charge, spattered off, leaving the positively charged ice behind.

The Vonnegut and Moore mobile laboratory at Langmuir Lab site, 1965. New Mexico Tech Archives.

It was later found that, although the Workman-Reynolds effect is real, the negative charges are bonded to the interface between the ice and the water and do not spatter off. Lightning has also been observed in "warm" clouds--ones that do not contain ice crystals--as well as in volcanic dust clouds. Nonetheless, many scientists still believe that the effect could account for charge separation in a typical storm cloud, although no single mechanism is likely to account for all charge separation in all clouds. The Workman-Reynolds effect is often combined with Lord Kelvin's hypothesis: falling rain carries the negative charges to the base of a cloud, leaving the positive ones at the top.

Vonnegut agreed that charged precipitation plays a significant role in cloud electrification, but he believed there was more to it--that charge could also be brought into the cloud from outside. He proposed in 1953 that positive space charge--clouds of positively charged particles known to exist above the ground--was carried to the top of convective clouds by the updrafts in the middle. The next step, as he saw it, was that the downdrafts around the clouds also carried negative charge downward.

Vonnegut's theory was ridiculed. In the mid-50s, many atmospheric scientists believed that there were no down-drafts during the development of a storm and that the winds converged instead of diverging at the cloudtop. If confirmed, this would have meant the end of the convective hypothesis. Vonnegut and Moore later found that a French scientist, Gaston Grenet, had proposed a somewhat similar mechanism in 1947. Grenet's theory had been ignored and was almost forgotten by the time Vonnegut learned of it in 1957.

Vonnegut had already created a stir by proposing that strong updrafts into the cloud base and divergent winds at the cloud top even existed in developing thunderstorms. By seriously proposing a hypothesis that most of their colleagues ridiculed, he and Moore left themselves no way out. They had to admit to a serious error or do whatever was necessary to vindicate their viewpoint. A few years later, a trip to Withington gave Moore a splendid, if serendipitous, opportunity to refine their hypothesis.

One drizzly afternoon in the summer of '58, the cloudbase enveloped the top of the mountain as Moore packed up his instruments to return to Boston. It had been a quiet cloud electrically--but suddenly lightning struck a nearby tree.

The event came as quite a surprise. Even more surprising was what happened a minute or two later. The instrument trailer Moore was in, having nearly been struck by lightning, was drenched by a gush of brief, heavy, localized rainfall. As he watched the storm's late-afternoon convective tantrum, lightning struck six more times in the vicinity. Each stroke was followed by a gush of rain.

Now his curiosity had been piqued. Obviously there was some connection between the lightning and the rain. This fact could be explained in terms of conventional theory: the falling rain, caused by God-knows-what, had brought negative charge close enough to earth for lightning to occur. But the more he and Vonnegut thought about it, the more the time lag seemed to suggest that the lightning might be causing the rain gushes. Very well and good, but they still had to prove it. Both rain and lightning were known to originate a kilometer or more up in the cloud. Moore had observed that the lightning came out of the cloud before the rain, but once again, correlation did not imply causation. Lightning travels much faster than raindrops. Perhaps the rain caused the lightning, just as orthodox thinking indicated, and the lightning simply beat the rain to the ground.

A long tradition existed in atmospheric physics of trying to relate rain gushes to lightning. Kelvin's hypothesis explained how falling rain could cause lightning. Earlier, Robert Hooke had noted a relationship between rain gushes and lightning in 1664. The Roman Lucretius had observed the correlation in 58 B.C. and concluded that thunder caused rainfall. Moore, ever on the alert for new sources of data, claims to have found a reference to the phenomenon in some translations of the Book of Exodus. In keeping with this tradition, Vonnegut and Moore figured out how lightning might trigger rain gushes, then published their own hypothesis.

Their explanation rests on the way that they envision the origin of a lightning channel high within a cloud. They believe that the channels do not branch so finely as to reach every charged droplet. Rather, they suggest that the top of a lightning stroke is only broadly tree-like, with branches but no twigs. The branches are channels densely packed with positive charge. They reach into cloud mass that contains negative charge, but at a comparatively low density.

Because oppositely charged particles attract each other, the positive particles move into the cloud and combine with negative ones. The bigger particle that results still has a positive charge, but not as much as before. These bigger, positively charged particles are attracted further into the cloud mass, where they hit and coalesce with more small ones.

As the process repeats itself, the particles keep growing. Before long they have grown into droplets and have been neutralized almost completely. As the droplets fall, they keep merging with whatever is in the way, but electrical charge no longer has much to do with it; all that is left is a mechanical process of collision and coalescence. Faster and faster these big drops fall until they come down as a rain gush.

Or so said Vonnegut and Moore. They worked out the mathematics of this process, which was quite plausible in theory. But they needed more than theory to prove their case to the scientific world. What they needed was an instrument that could tell them the precise order of events inside the cloud. The radars of that day were simply not up to the job.

In the meantime, some of the opposition to Vonnegut and Moore's theory was coming from Tech. Brook, an adherent to the conventional variation on Kelvin's hypothesis, does not doubt that rain gushes can occur after lightning. But he has also reported on a "lightning gush" in which lightning occurred after a heavy burst of hail. Why aren't rain gushes observed after lightning more often? Brook asks. He considers the phenomenon to be fairly uncommon; such organizations as the National Severe Storm Center in Norman, Oklahoma have searched for its origins in vain while studying other aspects of the relationship between rain and elecrification. Brook, who uses phrases like "tilting at windmills" and "beating a dead horse" to describe Moore's outspoken advocacy of the new theory, sometimes even hints that Moore enjoys his self-perceived martyrdom. In any case, Vonnegut and Moore have been tilting for a quarter of a century, and so far the windmills are still winning.

Another project that would have to wait was a direct test of Vonnegut's convective hypothesis. The controversial hypothesis suggested a good experiment: release space charge below a convective cloud and see what happens. A variety of schemes for his would be tried over the years, yielding suggestive partial results but no concrete evidence.

In the meantime, Moore and Vonnegut found other things to do. Moore tried ballooning on Mount Withington, with the idea of flying straight up into a thunderstorm in the gondola of a helium-filled plastic balloon. He was quoted as saying, "If the electric field gets too dangerous, we'll toss ballast and go through the top of the cloud." That turned out to be wishful thinking; he and his co-pilot, Lieutenant Commander Malcolm Ross, ended up miles from Withington, having proven once and for all that a balloon is not an appropriate manned research craft for thunderstorm work.

After three years of commuting between Massachusetts and Mount Withington, Vonnegut and Moore had some intriguing and significant results. Their principal work on Withington had been an extension of Reynold's and Brook's studies of the relationship between precipitation development and organized electrification in growing clouds. With instrumented captive balloons flown into the clouds and a radar directly below, Vonnegut and Moore found that organized electrification could be detected before the raindrops had grown large enough to be responsible for it. They also found again that gushes of rain often fell soon after nearby lightning.

Charlie Moore (left) presiding over the removal of the Tech hot-air balloon from a barbed-wire fence. New Mexico Tech Archives.

Other interesting phenomena were discovered: the end-of-storm oscillation (a lazy foul-to-fair-to-foul alternation of a dying storm's electric field) and curious electric-field excursions just before the arrival of rain. But despite their discoveries, the two were still not much closer to a thorough and basic understanding of the thunderstorm electrification process.

As Vonnegut and Moore surveyed the work that had yet to be done, they were dismayed by the prospect of commuting from Cambridge every year and working out of trucks all summer. September 1958 found Vonnegut at a cloud physics conference in Australia and Moore atop Withington packing up their equipment between rain gushes. With the truck loaded, Moore and Brook sat in a bar in the nearby village of Magdalena. Moore proposed that they jointly build a small, permanent lab on Withington. Brook was interested in the idea and soon passed it on to Workman, who, unknown to Moore, had once proposed such a laboratory on Sandia Crest near Albuquerque.

While all the scientists agreed that a permanent lab would be a good idea, they could not agree on where to put it. The New Mexico Tech scientists wanted it to be in the Magdalena Mountains, which were just east of Mt. Withington and the San Mateo range. This location would greatly simplify the logistics of supporting the lab and would permit line-of-sight microwave data transmission to Tech. Moore preferred Withington, where summer thunderstorms occurred three times more often than in the Magdalenas.

For a time, two independent efforts were made to build a mountaintop thunderstorm lab in the area: Moore's and Workman's. In mid-September, Workman wrote to the chief of the U.S. Forest Service to propose a joint New Mexico Tech-Forest Service project to build a road to the top of South Baldy Peak, the highest point in the Magdalenas. The Forest Service administrators in Washington were less than enchanted with the idea, but Workman kept trying.

In the meantime, Moore designed a lab building for Withington and secured the cooperation of forest rangers there. But when he went to the National Science Foundation for money in 1960, he ran into a stone wall. The NSF, which is supposed to fund university-affiliated research only, had no intentions of supporting such an effort on behalf of the Arthur D. Little Company. They liked the idea, however, and encouraged Moore to leave the company and become associated with Tech.

That looked like a difficult business for Moore, who had no Ph.D. and was a controversial figure to boot. Moore and Vonnegut gave their support to Workman's project, despite South Baldy's marked inferiority as a thunderstorm producer. As it turned out, however, Moore would have both a permanent mountaintop laboratory and a tenure-track associate professorship at New Mexico Tech by 1965.

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