Today, I noticed an interesting variant on a familiar pattern while walking along the beach: snow distribution sculpted by infrared radiation. An unexpected dusting of snow overnight had set the stage for the patterns.
Most people spend little time thinking about infrared radiation (IR), yet it is all around us. Everything emits in the IR by an amount (almost entirely) determined by its temperature. Rocks emit, trees emit, clouds emit, people emit. The warmer the object, the more energy is emitted.
Similarly, everything absorbs IR radiation from the things in its line of sight. So, an object loses energy based on its temperature, but gains based on what it receives from its surroundings. Whether an object’s temperature rises or falls depends on whether it gains more than it loses, or vice versa.
Consider the ground at night (so, we are not dealing with sunlight). If the ground temperature is, say 10C and the (effective) sky temperature is -20C, the ground will emit more IR radiation than it absorbs from the sky and so it will will cool: the ground temperature will drop.
That is assuming the ground has a clear (hemispheric) view of the sky, either because the surface is flat, or we are on the top of a ridge. But, what if we are dealing with the ground in a valley? The valley bottom will see only a portion of the colder sky, but also a portion of the warmer valley walls. It will end up warmer than the ridges owing to it also receiving from the warmer valley walls.
The first two pictures were posted three-and-a-half years ago as beach frost. They serve to set the stage for the last picture which was taken today.
That overnight, the footprint ridges have become cooler than the valleys is clear from the distribution of dew.
The same is true of frost: it forms preferentially on the colder ridges. Of course, unlike dew which darkens the sand, the frost makes the ridges appear lighter.
In the previous two pictures, the variation of temperature from ridge to valley determined where condensation took place. In the picture, below, it determines where melting takes place. A dusting of snow had covered the whole beach, but it melted first in the warmer valleys caused by footprints.
Anniversary bluebirds
Today marks the tenth anniversary of this website. It was launched on March 15th, 2005.
The original, and abiding, objective of the site was neither commercial nor promotional. It was merely a notebook of things learned about my surroundings. Had someone else built such a website, I would have been content to learn from it. No one else did, so I set to work.
Ten years later, the website and its blog receive about seventy-thousand page viewings a year. Most visitors are from Western Canada, but many come from other provinces and lands. Such numbers are small potatoes in the modern world of febrile social media. For me, relative obscurity is good: I am not a populist, but a backwater naturalist consulting his muse.
Yet, a decade does represent a satisfying anniversary for the project. How should it be marked? I thought about a reprise of favourite images, but decided that it would be more fun to just press on.
Fortunately, an observation this last week provided the ideal subject material, the Western Bluebird. (Thank you, Darcy Samulak for showing me where to find it.)
Locally, we encounter two species of the beauteous bluebird. I had seen the Mountain Bluebird other years (Puffed blue, Bluebird of unhappiness), but had not seen the Western Bluebird until last week. Unlike the Mountain, with its powder-blue breast, the Western has an orange breast and shoulders. The male’s colours are bright; the female’s are muted.
What a grand present: an anniversary bluebird.
The male Western Bluebird has a blue head and wings, but an orange breast and shoulders.
He is seen chasing some unsuspecting insect.
The female has muted colours.
She is seen here pouncing on and then wrestling with a larva.
Seen from the back, the male is strikingly ultramarine blue, sometimes with touches of orange.
