Weather Expert to Explain Tricks of Nature’s Light

In “All That’s Best of Light and Dark,” Bohren will explain why clouds, snow and other weather phenomenon appear to vary in brightness. The lecture, sponsored by the physics department at Wake Forest, will be at 8 p.m. in Room 101 of the Olin Physical Laboratory.

“Understanding the world we perceive visually requires blending psychology with physics,” Bohren said. “If we were equipped only with a knowledge of optics, our predictions about what humans perceive would be inaccurate or even ludicrous.

“Everyday life is rich with these and other examples (of the difference in perceived brightness of clouds and snow, wet and dry objects) accessible to everyone yet often escaping notice,” he said. “This talk is intended to be an eye-opener, both literally and figuratively.”

Co-author with Donald Huffman of “What Light Through Yonder Window Breaks?” and the editor of several papers and presentations on the scattering of light in the atmosphere, Bohren has drawn wide attention for his explanation of a phenomenon of severe weather known as “green thunderstorms,” in which observers report seeing green clouds before violent storms.

While other scientists have speculated that the thunderclouds themselves are not green but are framed against a backdrop of green airlight, Bohren believes the clouds themselves may appear green to the eye.

If the light is sunlight reddened at sundown, Bohren says that the blueness of clouds from water could cause a subtle shift in the perceived color of the clouds from blue to green. Since most clouds are so thin, and have so few particles absorbing water that the light they transmit is not markedly colored, Bohren believes only the most massive storm clouds are large enough to absorb enough water to shift the color of sunlight and produce the phenomenon of “green thunderstorms.”

For more information about Bohren’s lecture, call Natalie Holzwarth at 910-759-5510 or the Wake Forest University Physics Department office at 910-759-5337.