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The Brockenspectre and the Glory
Fri Oct 28, 2005
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Being high in the mountains has many rewards. Two not to be overlooked are the Brockenspectre and the Glory. Hi, I'm Bryan Yeaton for The Weather Notebook.
The Brockenspectre is just the observer's shadow cast onto a mist or cloud, often seen surrounded by a rainbow-like halo formed around the antisolar point. However, the shadow can often be several meters high. The name derives from a prominent peak in Germany's Harz Mountains the Brocken where mountaineers viewed the phenomenon in the early 1800s, and thought it a haloed spirit beckoning them.
Viewing the Brockenspectre requires standing above or in front of a cloud, or falling mist, with a bright sun directly behind you.
Sometimes, around the head of the Brokenspectre, is a ring of light known as the Glory. A glory appears when light traversing the cloud scatters back to the observer's eye. They are not rainbows, nor are they as easily explained.
In the returning sunlight, diffraction bends light slightly as it passes around the droplet edges. The degree of bending depends on the light's wavelength relative to the droplet size. Glories are 5 to 20 degrees across, with smaller droplets producing larger glories.
Diffraction produces light, dark, or colored bands by interference among overlapping light waves. The Glory's center generally appears bright with darker, often iridescent, rings around it. The more uniform the droplet-size, the more distinct the rings appear. Glories are often seen from aircraft flying above the clouds.
The Brockenspectre and the Glory don't just appear at high altitudes. With proper lighting, they can occur anywhere uniform-sized water droplets are suspended in the air.
Thanks to our contributing writer, meteorologist Keith Heidorn. The Weather Notebook receives funding from The National Science Foundation, and Subaru.
Today's Links
The Glory
http://www.sundog.clara.co.uk/droplets/glory.htm
The Brockenspectre and Glory
http://www.meteoros.de/glorie/glorie_b.htm
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