Rodney Campbell's Blog

More of this amazing hoar frost this morning. Growing crazily off the cold wire fences. This is perhaps old hat for those who live in colder climates. Myself however I rarely if ever get to see this.

Frosted II

NIKON D750 + 28.0-300.0 mm f/3.5-5.6 @ 180 mm, 1/320 sec at f/5.6, ISO 200

Hoar frost refers to white ice crystals. Deposited on the ground or loosely attached to exposed objects such as wires or leaves.

These form on cold, clear nights when conditions are right. Heat radiates out to the open sky faster than it can be replaced from nearby sources such as wind or warm objects. Under suitable circumstances, objects cool to below the frost point of the surrounding air. Well below the freezing point of water. These occur when ground-level radiation losses cool air till it flows downhill and accumulates in pockets of very cold air in valleys and hollows. Hoar frost may freeze in such low-lying cold air even when the air temperature a few feet above ground is well above freezing.

The name hoar comes from an Old English adjective that means “showing signs of old age”. It refers to the frost that makes trees and bushes look like white hair.

Tendrills

NIKON D750 + 28.0-300.0 mm f/3.5-5.6 @ 170 mm, 1/100 sec at f/8, ISO 100

It was a quarter to nine now and the sun is in theory well and truly up in the sky. We still can’t see the sun however through the still very dense fog in this valley. We’ve been shooting for almost two hours now but no-one is interested in stopping for breakfast yet. Awesome… 🙂

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