The difference between hoarfrost and rime ice coating Calgary
When winter rolls around, frost-covered trees in Calgary become one of the season’s most beautiful sights, and while many assume that it is hoarfrost, it can actually be another weather phenomenon called rime ice.
Daily Hive spoke to Christy Climenhaga, a scientist with Environment and Climate Change Canada (ECCC), to dive into what the difference between hoarfrost and rime ice actually is.
Climenhaga says a big difference between the two is how they look. Hoar frost tends to look light while rime ice appears to look heavier.
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“When you’re looking at rime ice, it’s a lot heavier. It’s not quite that feathery, light appearance that you see with hoar frost.” Climenhaga explained.
She also mentioned characteristics of the two, noting that hoar frost can often be blown off of surfaces like tree branches, while rime ice is much thicker and can be either soft or very hard depending on the wind when it is formed.
Climenhaga also explained how they are formed. “So if you’re looking at a cold, clear winter night in the prairies, and you wake up to that ice, and it’s been very clear, that’s when you’re looking at hoarfrost.
Rime ice, on the other hand, often forms on foggy nights as a result of water droplets freezing onto surfaces. “It’s often very cold, super cool droplets below zero, but stays liquid in the air, and then freezes onto very cold surfaces, creating that kind of milky, icy conditions.”
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So, if you’ve noticed the frost on Calgary’s trees recently, it’s likely you’ve actually been looking at rime ice, rather than the hoarfrost many assume it to be.
“If you’ve got a lot of fog day after day, you can get very thick rime ice, and that’s kind of what we’re seeing in the Calgary area,” Climenhaga says.
Climenhaga also spoke about the differences between the effects of hoarfrost and rime ice and how rime ice can potentially cause more issues. Due to its weight and thickness, rime ice can cause issues with power lines if it freezes onto them, as well as affect trees and freeze onto aircraft.
“It can build up and be really, really heavy, whereas hoarfrost is so light it can get blown away very easily.”