A Winter’s Frost
A few days ago a friend of mine Elisa Campbell posted an account to my Eastern Native Tree Society of frost crystals she encountered. She wrote: “On Christmas morning I hiked up part of the Mt Holyoke Range in the middle portion of the Connecticut River valley of Massachusetts. The weather was foggy – as I approached the range, I couldn’t see any mountains at all” Upon finding the frost crystals she goes on, “It wasn’t like when we get freezing rain and it looks as if the twigs have been encased in glass; instead, there were millions of little ice crystals attached to things like spikes, thorns, or needles; some were attached to each other, forming a dangling chain like a Christmas tree decoration (harder to photograph with my little pocket camera). Beech branches looked as if they had sprouted a multitude of protective spiky thorns.”
http://groups.google.com/group/entstrees/browse_thread/thread/e13c7dbc8644c083?hl=enPlease check out the link above to see some of the photos.This started a longer discussion about frost crystals. I commented that the photos of the Hoarfrost looked beautiful. There was some questions and debate about the nature and name of the type of frost crystals seen. There is a lack of consensus about the names of different types of frost crystals.
In usage the definitions seem to generally agree that “hoarfrost” forms directly from water vapor, while “rime” forms from water droplets in fog or cloud freezing on a cold surface. The crystals in Elisa’s photos seemed more feathery to me suggesting they are hoarfrost, formed directly from water vapor rather than the more solid icy form of rime.
Specifically it looks much like what is in Wilkipedia as: Advection Frost, a subset of hoarfrost.http://en.wikipedia.org/wiki/Frost
Advection frost (also called wind frost) refers to tiny ice spikes forming when there is a very cold wind blowing over branches of trees, poles and other surfaces. It looks like rimming the edge of flowers and leaves and usually it forms against the direction of the wind. It can occur at any hour of day and night.
This discussion started me on a search on the Internet for different photos of frost crystals. The variety I found on the web is amazing. I am looking forward to examining frost crystals this winter and trying to photograph as many as possible.
I remember in another discussion of photography tips about photographing clear or translucent objects. The key to getting good definition of the subject was to place a dark black background behind the clear object and to then use side-lighting or an angled back lighting to highlight the object. Time to experiment.
The image above is by Limulus, Picture of frost on a hedge in my backyard, Saskatoon, SK, Canada, December 4, 2009. This file is licensed under the Creative Commons Attribution ShareAlike 3.0 License. In short: you are free to share and make derivative works of the file under the conditions that you appropriately attribute it, and that you distribute it only under a license identical to this one.