Before the start of the aviation era, the sight of a glory — one of the more striking optical phenomena in meteorology — was rarely seen except by mountain climbers.
A glory is rings of colored light, mostly magenta and yellow, that surround an aircraft’s shadow against the top of clouds or a fog bank — such as those of a saint’s halo. If you look down on a cloud from an aircraft or even from a very tall structure when the sun is out, you can sometimes spot one.
Like a rainbow, a glory appears opposite the sun with the viewer in the middle. The colors are produced by tiny water droplets in low-level clouds that act as tiny reflectors of the sunlight.
As you fly along in an aircraft, the size of the glory will change depending upon the diameter of the water droplets in the cloud. As the size of the water droplets decrease, the diameter of the glory will increase.
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To produce a glory, the clouds must contain water droplets, however, and not ice crystals found in colder and higher-level cirrus or cirrostratus clouds. While ice crystals don’t work well in creating glories, they’re perfect for producing sundogs — halos that surround the sun — or other phenomena such as silver-blue night shining clouds or circumhorizontal arcs called fire rainbows that are caused by light waves bending around the crystals.
The colors can be brilliant, much like the feathers on a hummingbird.
According to Cliff Mass, an atmospheric scientist at the University of Washington, glories can be produced using the equations that describe electromagnetic waves and their interactions with droplets. According to Mass, a glory can be created when the diameters of atmospheric particles are similar to the wavelengths of the scattered light — known as Mie scattering.
At this time, however, the scientific description of glories is the subject of much debate.
Charles Thomson Rees Wilson, a Scottish physicist and meteorologist, worked as a temporary observer at the Ben Nevis weather station on the highest mountain on the British Isles at 4,409 feet. Motivated by the sight of a glory and other meteorological phenomena from this weather station, he built a sealed container for creating clouds at Cavendish Laboratory in Cambridge.
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PG&E safety tip: Take steps now to stay safe in the event of a power outage. Keep a battery-operated flashlight and radio within easy reach. Use safer LED candles. Wax candles are not recommended. Plan for another way to communicate. Don’t depend on a phone that requires electricity. Keep a standard handset or mobile phone ready as a backup. Store water-filled plastic containers in your freezer. You can use them as blocks of ice to prevent food from spoiling.
For more PG&E safety tips, visit www.pge.com.