science | BC Write

The bridge over the creek near my home always provides me with interesting photos.

Freshly-fallen snow can be a beautiful and magical sight. Snow has some disadvantages and even some dangers, including its cold temperature and the problems that it can create for travellers. When I’m wrapped up in warm and waterproof clothing and travelling through snow is a choice and not a requirement, however, the surroundings can be delightful.

I enjoy taking walks in the snow and taking photographs of the scenes that I see. I admire the beauty of nature, and I find the science of snow intriguing. I don’t drive in snow unless I have no choice, but walking through a snowy landscape is always interesting. In this article, I include some of my photos of snowy days and facts about snow discovered by scientists. I took the photos while it was snowing, which is why there is what appears to be mist in them.

Snow in the Lower Mainland Region of British Columbia

This winter has been unusually snowy for my part of the world. The lower mainland region of B.C. generally has wet winters with relatively mild temperatures. Any snow that arrives doesn’t last for long. This year has been different. We have had several snow events. The latest one in particular has hung around for a while, though as I write this the rain is falling and the snow is slowly disappearing. It hasn’t vanished, though. The temperature isn’t high enough for all the snow to melt.

Effects of Snow on Sound and Insulation

Snow can form attractive landscape scenes. It also has some interesting properties. Some people may have noticed that immediately after a heavy snowstorm outdoor sounds seem hushed. This is not due to their imagination. Freshly fallen snow that is still fluffy contains spaces that trap sound waves. These spaces disappear as the snow settles.

If snow becomes ice, the effect on sounds is different. The surface of the ice reflects the sounds. This can cause them to travel for longer distances and also make them clearer.

Though surface snow is cold, under some conditions it can be a good insulator. This ability is the result of air spaces in the snow. The spaces can trap heat and prevent it from escaping. It’s important to remember that in some cases it can be dangerous to be surrounded by snow. If someone wants to build a snow shelter, expert advice is required in order to stay safe.

The electromagnetic spectrum (Public domain image from NASA)

The Electromagnetic Spectrum and Visible Wavelengths

Snow is not always white. To understand why, it should be helpful to know a little about the electromagnetic spectrum and the visible light section of the spectrum. The term “electromagnetic spectrum” refers to the differing wavelengths of electromagnetic radiation, as shown in the illustration above. The wavelengths form a continuous sequence and are traditionally shown from long to short wavelength (and therefore from low to high frequency).

Readers may remember the acronym Roy G. Biv from their childhood school lessons. The name is a good way to remember the colours of the visible spectrum, which is a small section of the electromagnetic one. From the longest wavelength to the shortest one, the colours in the visible spectrum are red, orange, yellow, green, blue, indigo, and violet. A rainbow is a good illustration of the colours in the visible spectrum. It’s created by the effects of raindrops on visible light rays that strike them.

There is no such thing as colour without eyes to perceive it. You require eyes that are capable of differentiating between light of different wavelengths and a brain that can process the data in order to perceive colour.
Dr Suzanne Williams, Natural History Museum

Reflection, Refraction, and the Colour of Objects

An object’s colour depends on the light rays that strike it and the effect of the object on those rays. It also depends on the particular light rays that the object sends to our eyes and the brain’s interpretation of what they mean.

If an object reflects all of the incoming wavelengths in the visible spectrum to us, such as fresh snow does, it will appear white. If it absorbs all of the wavelengths and reflects none of them, it will appear black. If the object reflects only one or only some wavelengths, they are used by the brain to create the sensation of a particular colour. The first small illustration in the video screen above shows reflection.

Refraction of light also affects the colour that we perceive. Refraction is the bending of light rays as they pass from one medium to another. The process can change the wavelength and frequency of light, which affects the colour that we detect. The second illustration on the video screen above shows refraction.

Additional factors in the environment can affect the wavelength of light that we detect. The effects of our surroundings on wavelength and the brain’s interpretation of the results are very interesting to explore. It’s also interesting to note that some animals have different visual senses from us. Some insects can see ultraviolet light, for example, which is invisible for our body.

This double rainbow in Alaska is an example of the visible spectrum. If you look carefully, you should be able to see the fainter second rainbow above the darker one. (Photo by Eric Rolph at English Wikipedia, CC BY-SA 2.5 License)

Why is Fresh Snow Usually White?

The fact that fresh snow is white may seem puzzling, since snow is made of colourless ice crystals that are translucent. Transparent objects transmit the light rays that hits them. Translucent objects are not completely transparent, however. They refract some of the light rays that strike them. The total refraction in a patch of snow that contains multiple crystals is enough to create white light for our eyes and brain.

Blue, Green, Pink, and Red Snow

Snow isn’t always white. It may sometimes be other colours. Deep snow absorbs more red light than blue light. As a result, the light reflected by deep snow and reaching our eyes can make the snow look blue.

Snow may also be green due to the growth of green algae on its surface or just under the surface. It might seem strange that an alga could survive on snow, but researchers have found that multiple species can do so. Life often finds a way to succeed, even in seemingly strange habitats. The green algae in snow are unicellular but grow in groups, so they can be seen with the naked eye.

Snow on the ground sometimes has pink or even red patches and may be referred to by the interesting name of watermelon snow. This colour is also produced by unicellular algae, including Chlamydormonas nivalis. The species is sometimes pink in colour but is classified as a green alga. For part of its life, it is green. When snow arrives, the reproductive cells develop pigments called carotenoids, which have an orange to red colour.

Blood Falls, in Antarctica’s Taylor Glacier, also has red snow, but for a different reason. There, the deep red color is caused by saltwater leaking from an ancient reservoir under the glacier. This water is rich in a form of iron that oxidizes when it comes into contact with the atmosphere.
National Snow and Ice data center

I took this photo from a trail beside a road leading to a golf course.

Yellow, Grey, Brown, and Black Snow

Many people probably think that yellow snow is caused by the presence of urine. They would often be right. Air pollution can also cause yellow snow, however. In late winter or very early spring, pollen from plants can do the same thing. In some cases, snow can be yellow even as it falls.

Similarly, although muddy and dirty footprints and vehicle tires can turn snow grey, brown or black, so can air pollution such as soot. In addition, dust or sand from one area is sometimes carried by the atmosphere to another one, causing yellow to brown snow to be produced.

I was standing on a walking and cycling trail beside the road when I took this photo. I was most attracted by the snow-covered tree overhanging the path.

Extreme Weather (for Metro Vancouver)

Snow is a fascinating substance. It often looks like a simple white deposit, but it has multiple features and abilities. The science of snow is interesting. There is no doubt that the substance can cause problems, however, at least where I live.

Though some of the snow has disappeared from my neighbourhood, strange weather in the region continues. I live in a part of the Lower Mainland area known as Metro Vancouver, which is located near the ocean. Some parts of the region are currently experiencing strong winds, freezing rain, and flooding. The seawall in the area’s popular Stanley Park has been damaged by the ocean. I’d rather have snow than these weather events. It can be enjoyable to observe and study.