Adam Cloud Photograph: Mystery Solved!
April 10, 2013
Remember the Peanuts comic strip in which Linus points to the clouds above him and says he sees a map of British Honduras and the Stoning of St. Stephen? Charlie Brown, on the other hand, sees a duckie and a horsie.
For John Adam, University Professor of mathematics at Old Dominion University, his "eye" tends toward Linus'.
During the last decade, Adam, a nature photographer of some renown, has published nearly 50 photographs on the Earth Science Picture of the Day website. These include photos of clouds, all of which conjure up figures and themes that are much more complex than a duckie and horsie.
His latest contribution to the website - which insiders call EPOD - just may be the most complex yet.
Adam snapped "Deceptive Skies" during spring break this year while he was in the village of Bildeston, Suffolk, in his native England. "It was late afternoon on a chilly mid-March day. Surely the solid-looking cumulus congestus near the horizon was casting its shadow onto the high and much brighter cloud bank," Adam wrote in a summary of the cloud image.
He said he contacted James Foster, the scientist who oversees EPOD, and was assured that the photo was one that would qualify for publication. But the more Adam thought about the image, the more he realized something was wrong.
"I had written up a summary of what I thought was going on in the picture, but after thinking about it for a while I realized that it was not as simple as I thought. I decided to contact my friend Les Cowley, who created and maintains two superb 'sister' websites: Atmospheric Optics and Optics Picture of the Day. He is probably the foremost world authority on meteorological optics, and, to quote him, 'This picture gets more and more interesting.'"
"It appears at first as if the sun was behind me and casting a shadow of the cloud ahead of me," Adam said. "But the camera was facing in the opposite direction, almost toward the sun, which was to the right and just outside the field of view."
Adam next consulted with Ian Loxley of the Cloud Appreciation Society to identify the nature of the lower translucent cloud, and then Adam and Cowley together came up with a summary that was accepted along with the photo by EPOD.
"I named the photograph, very accurately I think, "Deceptive Skies," Adam said.
"The sky is not always what it seems," the final analysis notes. "The camera was facing in the opposite direction, almost toward the sun, which was to the right and just outside the field of view. And the sun's rays almost never shine upwards! So what is happening?"
As Linus might tell us, dense cumulus congestus clouds can tower up to 20,000 feet. In "Deceptive Skies" these clouds are casting a shadow downward onto thin, translucent clouds, possibly altocumulus stratiformis, that are actually at a lower altitude and closer to the camera, according to the summary.
"A trick of perspective makes the near and lower cloud, together with the shadow projected onto it, appear to be higher in the sky," Adam and Cowley write. "We see the shadow from the other side of the cloud, just like looking at the back of a movie or cinema screen."
Got that, Charlie Brown?
The summary continues on in Linus-like detail and can be read at http://epod.usra.edu/blog/2013/04/deceptive-skies.html.
Adam, who received his Ph.D. in theoretical astrophysics from the University of London in 1975, is the author of "Mathematics in Nature: Modeling Patterns in the Natural World" (2003 Princeton University Press). He co-authored "Guesstimation: Solving the World's Problems on the Back of a Cocktail Napkin" (2008 Princeton) with ODU physicist Lawrence Weinstein. More recently he has authored "A Mathematical Nature Walk" (2009 Princeton) and "X and the City: Modeling Aspects of Urban Life" (2012 Princeton).