Snow, though not a new experience for most of us, has an enormous amount of science behind it that answer some of the most interesting questions. Let’s address some of those questions, here.
What is snow?
Snow starts with a single snow crystal which is formed when water vapor freezes, and as it falls it morphs into a hexagonal shape. At some point, collisions with other snow crystals occur. This combination of snow crystals slamming into each other increases in size until it becomes a snowflake. Since snow is an accumulation of packed ice crystals, the state of the packed snow determines a variety of characteristics, such as temperature, color, and the amount of water contained in the snow. As weather conditions vary, the snowpack can also change, and this in turn affects the attributes of the snow.
The surface characteristics of the snow after a snowfall are dependent upon the configuration of the crystals as they were formed and on the weather conditions at the time of snowfall. Let’s say the snowfall occurs along with strong winds, the snow crystals are splintered into smaller fragments and will thus be more densely packed. Snow may melt or evaporate, after a snowfall, or it may stay on the ground for extended periods. If snow remains on the ground for any length of time, the size, texture, and shape of individual snow grains will change even if the temperature of the snow stays below freezing, or if the temperature rises, they may melt and refreeze when the temperature drops again, and will at some point, be compacted by subsequent snowfalls.
The snowpack usually accumulates over the course of the winter months and develops a complex structure made up of layers of assorted snow grains, which reflect the prevailing weather and climate conditions at the time of the snowfall, as well as internal changes to the snow cover as time goes on.
For example, warm temperatures mean higher levels of moisture, thereby creating wet snow. In warmer, more moist conditions, the edges of each snowflake to melt, thus causing them to stick to one another, producing bigger, heavier snowflakes.
Colder weather conditions result in less moisture, creating dry snow. Since these snowflakes do not stick together they are much smaller, and lighter, These flakes are often referred to as “powder”, and are preferred for skiing.
Snow requires moisture in the atmosphere. Snowfall is also relative to temperature, but not necessarily the ground temperature. Snow forms when the atmospheric temperature is at or below freezing (0 °C or 32 °F). Typically, the temperature on the ground must be at or below freezing for the snow to reach the ground. However, it’s possible for the snow to still reach the ground when the ground temperature is above freezing if certain conditions exist. In this scenario, snowflakes start to melt as they reach this higher layer of warmer temperatures. However, the melting princess produces evaporative cooling, which cools the air immediately around the snowflake, thereby slowing down the melting process. As a rule of thumb, snow will not form if the ground temperature is at or above 5 °C (41 °F).
Although it will not snow if it is too warm, it is never too cold to snow. Snow can materialize at remarkably low temperatures, provided there is a source of moisture and a mechanism to cool and lift the air mass. The majority of heavy snowfalls occur when the air near the ground is comparatively warmer, -9 °C (15 °F) or warmer.
Snow development requires moisture, which means very cold, but very dry areas may seldom experience snow. Valleys in Antarctica are freezing but extremely dry, resulting in minute amounts of snowfall.
Is snow always white?
Is snow always white? Snow generally appears white. This is because the full spectrum of visible light is white. Most of the visible light hitting the snow or ice is reflected without absorbing any particular frequency of light. Objects appear to be a certain color because they reflect that color. Virgin snow reflects most of the visible sunlight, thereby appearing white. The amount of the snowpack’s reflectivity is referred to as its albedo.
Snow may also appear to be blue. Ice grains scatter a large amount of light. When light waves travel any appreciable distance, they must keep scattering to not be absorbed. When one observes the light coming back from near the surface, where it has only been scattered a short distance, the snow will still appear white.
More red light is absorbed by the snow than blue. The difference is miniscule, but over a substantial distance, for example, a meter (3.3 feet) or more, the snow layer reflects more blue light than red light, so if you dug a hole in the snow a meter deep, the snow at that depth would appear blue.
Organisms in the snowpack may also change the color of the snow. Watermelon snow appears pink or red due to a species of fresh-water algae that thrive in cold conditions and contain a bright red pigment. Watermelon snow is most common during the summer months in high mountains regions, as along coastal polar regions. Blood Falls, in Antarctica’s Taylor Glacier, has snow that appears deep red, and is caused by saltwater emanating from an ancient reservoir under the glacier. The water contains large amounts of a type of iron that oxidizes upon contact with the atmosphere, creating a blood-red waterfall. Other types of algae can create green snow. Pollutants such as soot can cause the snow to be gray or blackish. And of course, we all know that yellow snow is caused by the presence of urine.
Why is it always quiet after a large snowfall?
Why is it quiet after a large snowfall? The reason is that snow is able to absorb sound because it is porous. Snowflakes are six-sided crystals that are filled with open spaces. Those spaces absorb sound waves, resulting in quiet surroundings.
A small amount of snow won’t absorb much sound. Usually, a few inches of snow is required to have appreciably dampened sound waves.
As snow loses its silencing ability as it melts. The size of the spaces between the crystals is reduced as it melts. As temperatures oscillate in winter, new snow can partly melt and then freeze. Once snow becomes ice, instead of dampening soundwaves, it amplifies sounds since ice reflects sound waves instead of absorbing them.
