John, thanks for bringing this up.
First time I had ever heard of Rime Ice was two days ago in town. The vast majority of people were calling it Hoarfrost. Not even my wife, who is from the north, had heard of Rime Ice before.
Now for the real kicker. I did a web search to see what the difference is. Found this site:
https://www.dtn.com/rime-ice-or-hoar-frost-there-is-a-difference/
According to the article, Rime Ice comes in two types; hard and soft. The article states:
[i:566f245cbe]Hard rime is often very dense, and an entire tree may be coated evenly with it, as seen in the image below. This type of ice occurs due to freezing fog when wind speeds are high, and temperatures are in the range of 17-28F.[/i:566f245cbe]
[i:566f245cbe]On the other hand, soft rime is not as thick and may appear fragile or sugary. When you take a close look, you can see how it has individual spikes. It is more likely to happen during a freezing fog when winds are calm.[/i:566f245cbe]
[i:566f245cbe][b:566f245cbe]Hoar Frost[/b:566f245cbe]
On a calm, clear night, ice crystals may attach to grass, leaves, and branches. Humid air will skip the droplet stage and go straight to crystallizing. When the sky is clear, the temperature can quickly drop since there are no clouds providing insulation. As the surface of a snowfield rapidly cools, the interior ends up warmer than the exterior. This heat will radiate out along with humidity from melting snow, and the moisture then contributes to the growth of the frost.[/i:566f245cbe]
Our temps have been below 0F at night and into the single digits above in the daytime. Winds have been calm. Air has been crystal clear, EXCEPT when these huge waves of fog come dropping down (low clouds with LOTS of moisture).
Our temps exclude Hard Rime. So what about soft? The article states that soft looks sugary, but close inspection looks like it's made of tiny ice spikes. That last part leaves this out, as our frost is just as blunt as can be, and largely looking like it is made up of flat snowflakes.
No matter how one looks at it, I [i:566f245cbe][b:566f245cbe]think[/b:566f245cbe][/i:566f245cbe] what we have would technically be described as Hoarfrost. All I know is, this frost is beautiful!! It's also very rare! This is the only time we can remember an event like this in the time we've lived here, which is roughly 20 years. This is also a wetlands area, but not sure that has a lot to do with it other than the ground here is some of the lowest around.
I've lived in MN since 1998, and am just now learning about Rime Ice. Had never heard of Hoarfrost until a few years ago. So PLEASE don't tout me as being some sort of expert. That couldn't be further from the truth. And that's why I thanked you for bring up the subject, as it's the perfect chance for me to learn more about the environment in which I live. I may be Texas born-N-bred, but I absolutely LOVE winter!
A comment I told the wife on the way to town was, I bet it would be easy to get lost in the woods with all this frost. Makes everything look too much different. I suppose one could knock the frost off of limbs to mark the trail....so long as they didn't end up in the same spot the next day. I guess true northern outdoorsmen would have some good ideas about that, but I'm not one of those. I'm basically just a long-term tourist up here. :wink:
