Frost kills our plants in the fall. It is the precursor to winter, and conjures up images of frozen pipes, windshields to be scraped, and cold fingers and toes. We have to wait for it to get out of the ground before we can do any serious digging, and it can single-handedly wipe out an entire year’s worth of apples, if timed correctly. Not exactly something you look forward to. But have you ever looked at it closely?
Frost on the hood of a car.
There are actually a number of types of frost. There is the usual, garden variety kind (pun intended), frozen ice crystals that are dusted over everything on a cold morning in fall. But then, there are its more complicated cousins, hoar frost and rime. Hoar frost happens when the night is cold and clear, and the air is “super saturated”, meaning the humidity level is greater than 100%. This results in a super-cooled dew that freezes quickly and grows into impressive ice crystals that grow on everything like a white beard, making the landscape look like it has been covered in snow.
Rime happens when fog freezes rapidly. The effect is a lot like hoar frost, except that it tends to be located only on the windward side of things, where the fog has been blown up against the unprotected side.
Looking closely at any of these frosts, it’s hard not to be impressed by the beauty and complexity of Mother Nature’s winter endeavours. Until it’s time to scrape those endeavours off the windshield, of course, and then it’s time to come back to reality!
Below are pictures of a December hoar frost in England.
And, because no discussion of frost and rime would be complete without a Robert Frost poem about winter…
Looking for a Sunset Bird in Winter
by Robert Frost
The west was getting out of gold,
The breath of air had died of cold,
When shoeing home across the white,
I thought I saw a bird alight.
In summer when I passed the place
I had to stop and lift my face;
A bird with an angelic gift
Was singing in it sweet and swift.
No bird was singing in it now.
A single leaf was on a bough,
And that was all there was to see
In going twice around the tree.
From my advantage on a hill
I judged that such a crystal chill
Was only adding frost to snow
As gilt to gold that wouldn’t show.
A brush had left a crooked stroke
Of what was either cloud or smoke
From north to south across the blue;
A piercing little star was through.