Hoarfrost Crystals on My Rain Gage

February 22, 2017

Hoar Frost b (2)

Photographer: Marion O. Weaver
Summary Authors: Marion O. Weaver; Jim Foster

Shown above is my backyard rain gage, near Olmstedville, New York, coated with hoarfrost crystals. On this January morning, rather large crystals covered the gage and almost everything else fully exposed to the sky. The temperature at the time the photo was snapped (about 8:00 a.m.) was 11 F (-11.5 C). Though I occasionally notice hoarfrost on my weather instruments, these crystals were particularly noteworthy. Hoarfrost grows best when the air is not only very cold, but moist as well. As you can tell from the photo my gage is located in an open area toward the bottom of a slope, and not far from a stream – the likely source of water vapor for the crystal growth. Later in the morning, these hoarfrost crystals sublimated in the warming sunshine. Photo taken on January 16, 2017.

Photo Details: Apple iPhone 6s Plus; 1/718 sec. exposure; f/2.2; 4.15 mm (35 mm, eq:29 mm).

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