The science behind rime ice

The video above shows a form of winter-time precipitation called rime ice coating the trees on top of Clinch Mountain in Virginia. While rime ice is beautiful, it can cause travel trouble.

So what is rime ice? Rime ice is a type of frozen precipitation that forms when supercooled liquid droplets freeze onto surfaces. The droplets usually come from fog or low-lying clouds, and they freeze instantly upon contact with a surface that is at or below freezing temperature.

Rime ice is often white and feathery in appearance, and it can accumulate rapidly, making it a significant hazard to aircraft and ground transportation. Rime ice is also known as "hoar frost" or "soft rime."

The feathery texture of rime ice is caused by the way the supercooled droplets freeze. As the droplets freeze, they release heat, which causes the surrounding air to expand rapidly. This expansion causes the droplets to break apart and form a mist, which then freezes to form feathery crystals of rime ice.

Rime ice typically forms on exposed surfaces, such as the leading edges of airplane wings, power lines, and trees. It can cause problems for aircraft by adding weight to the wings, increasing drag, and altering the airflow over the wings, which can affect the plane's lift and control. Also in some outdoor activities like climbing and hiking, rime ice can pose danger by making the surfaces slippery and unstable.