The Science of Leonardo's Storm Drawings

WE should have paid more attention to Leonardo da Vinci's storm drawings. His insight into thunderstorm downburst winds might have helped avoid some aircraft disasters in our time. The relevant scenes appear in the 11 drawings called ``Deluge or Visions of the End of the World'' that Leonardo executed late in his career. The drawings of wildly swirling winds attacking land and water have seemed to be unnatural fantasies. But Stanley D. Gedzelman of the City College of New York's Department of Earth and Planetary Sciences finds them astonishingly true to meteorological reality.

In a paper published in the Bulletin of the American Meteorological Society, Professor Gedzelman shows that Leonardo's presumed fantasy accurately portrays the downburst phenomena. You can see winds flowing downward from beneath a thunderhead to form a whirling vortex that spreads out rapidly over the ground. This kind of outflow, invisible unless it picks up dust, can catch the unwary off guard.

Just such an encounter caused the Eastern Airlines crash at New York's Kennedy Airport on June 24, 1975. This tragedy sparked the modern research that has shown the nature, prevalence, and danger of downbursts. Now air-traffic controllers and pilots know what to look for.

``These findings have probably saved hundreds of lives already, but hundreds more might have been saved if credence had been given to da Vinci's `Deluge' scenes,'' Gedzelman observes.

Leonardo was not the first artist to notice storm winds or to be intrigued with vortexes; many artists have depicted atmospheric phenomena realistically. But, while meteorologists can appreciate Constable's clouds, they generally don't look to artists for help with science. Leonardo, who was both an artist and a scientific researcher, should have had a stronger claim on their attention.

Gedzelman points out that Leonardo based his downburst drawings on both astute observation and specific experimentation. In fact, the Renaissance engineer took the same care to understand the fluid dynamics these drawings reveal as he did to understand the anatomy that guided his sculpture. He used water as his ``model'' fluid for his research and employed techniques still used by fluid dynamicists to trace flows. Sawdust and other materials served as flow tracers. Shadow patterns on the bottom of well-lit shallow basins revealed waves and other motion.

Modern scientists would be uncomfortable with Leonardo's theoretical explanation of his findings, for he thought in terms of Aristotle's physics. But keen observation enabled him to depict the physical phenomena correctly. ``Remember first, when discoursing about water to adduce first experience and then reason,'' he wrote.

Summing up his assessment of Leonardo's work, Gedzelman says: ``His explanations of convective clouds constitute a mixture of classical ideas, replete with their misconceptions, and his own incisive reasoning based on careful observation and experiment.... [He used the latter] to obtain a far better visual and conceptual picture of thunderstorms than anyone before him.''

So much for the thesis that the ``Deluge'' drawings are the fantasies of an old man who could no longer get his act together. It's unwise to discount the work of a proven genius just because it may seem bizarre. It may well hold wisdom from which posterity can profit.

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