Physics Photo of the Week

October 21, 2022

First Rime Ice - Fall 2022

This Wednesday morning (October 19, 2022) brought the first rime ice deposit on the Great Craggy Mountains overlooking Warren Wilson College in the midst of fall colors.  This is a sign that winter is about to descend.

The whiteness on top of Craggy Gardens, which I call "Craggy", is due to the frost on the twigs and remaining leaves on the trees of the mountaintop at high elevations (higher than 5000 ft above sea-level).  What looks like frost from a distance, is frozen cloud droplets, that were below the freezing point while within a descended cloud.  The cloud droplets were super-cooled below the freezing point of water (32 deg F).  As soon as the droplets collided with a leaf or twig, they were stimulated to freeze immediately because the twigs and leaves provided nucleation sites to attract the crystallizing super-cooled water.


A much more vivid color photo was made the last time Physics Photo of the Week posted a feature on "Rime Ice" (April 3, 2020) shown again at left. 

The early winter shown this year (2022) and late winter in the spring of 2020 are statistical "flukes" of the on-going trend of global warming. Last year PPOW published a "a peak of the fall colors" on Nov. 11, 2021 of a photo taken on October 29.  That is 2 weeks later than this week's peak of fall colors.  However when we look at the 50 year trend of statistical averages, the effects of global warming are alarming.

An up-close photo of rime ice was featured in the February 22, 2022 post.

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department. These photos feature interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation. Atmospheric phenomena are especially welcome. Please send any photos to dcollins@warren-wilson.edu.

All photos and discussions are copyright by Donald Collins or by the person credited for the photo and/or discussion.  These photos and discussions may be used for private individual use or educational use.  Any commercial use without written permission of the photoprovider is forbidden.

Observers are invited to submit digital photos to:

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