Page 140 - James Rodger Fleming - Fixing the sky

relating to fog as a physical entity have at once fascinated the untrammeled mind
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of the wild inventor and harassed the mind of the cautious investigator.” This
was written in 1938 by Edward L. Bowles, director of the Round Hill Research
Division at MIT and supervisor of its fog research.
Undoubtedly, MIT meteorologist Henry Garrett Houghton Jr. (1905–1987)
considered himself a “cautious investigator” engaged in fog research, and
most certainly he regarded Warren as a “wild inventor.” The theoretical pro-
cesses involved in precipitation formation—the Wegener-Bergeron-Findeisen
ice crystal process (in cold clouds) or the collision-coalescence process (in
warm clouds)—had only recently been defined. In 1935, working on the basis
of research done by Alfred Wegener, Norwegian meteorologist Tor Bergeron
published his hypothesis that the growth of ice crystals in a cloud containing
both ice and water droplets could lead to precipitation; three years later, Walter
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Findeisen clarified and expanded on Bergeron’s ideas. The key to fog removal
seemed to lie in the reversing of these processes.
In 1938 Houghton and his colleague W. H. Radford surveyed the various
approaches to fog removal and categorized them as physical, thermal, or chemi-
cal removal methods. Here is a synopsis of his report:

n Physical methods. one imaginative approach to freeing airfields from fog
involved the installation of powerful fans and ventilation ducts beneath the run-
ways to provide a fresh-air circulation system. This technique would not work,
however, if the airport was covered by a large fog bank and the fans merely cir-
culated moist air. Another plan envisioned forcing a stream of air through a set
of baffles to slow it down and to condense some of the moisture on contact, but
such an apparatus would likely be huge, inefficient, and impractical.
What about high-intensity sound waves? Experiments had demonstrated
that they could clear the air of smoke and dust. The theory was that the energy
generated by the sound echoing off the walls of a small, enclosed space triggered
the precipitation of suspended matter in the air. But an airport is not a table-
top experiment. It is not an enclosed space. Fog particles in the free air are much
larger than smoke or dust particles, and air travelers and airport neighbors could
not safely or pleasantly be subjected to high-intensity sound waves every time the
fog rolled in.
What about electricity? Warren’s technique of sprinkling electrically charged
sand above fog or clouds should, in theory, lead to the coalescence of the cloud
droplets. In practice, however, it was fraught with practical problems and had
met with only limited success. Alternatively, spraying charged water drops might
also be effective, but could result in the formation of additional fog. An electrical

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