Nature is filled with many clues that can tell us about the conditions in the environment. In winter, one of these clues is the snowflake! It's common knowledge that each snowflake is unique, but each snowflake can tell us a lot about what is happening in the atmosphere around and above us. Snow falls in many forms, and the common names for these types of snow are snowball snow and powdery snow. Why does snow fall in these different forms? Why are some snowflakes smaller than others? Why does snow sometimes fall when it’s above freezing? Let's get into it!
Snow needs moisture and humidity in the atmosphere to form, so very dry places will not accumulate snow even if it is below freezing. This includes areas of Antarctica! Since warmer air holds more moisture, it tends to be less humid the further the temperature falls below freezing. Snow is formed simply by formation of ice crystals on particles of dust and the combination of these ice crystals in the atmosphere until they become so heavy that they fall to the Earth. Moisture is the most important factor for snow to form. Although snow is less likely to form when the temperature is below 0oF (-18oC), there is no minimum temperature for snow to form.
When the air temperatures are warm enough in the atmosphere, the snowflakes melt a little around the edges. Because water likes to stick to itself, the snowflakes combine in the air before reaching the cooler layer below. Once they fall down into a colder layer of air, they refreeze and form large clumpy snowflakes. This is what creates snowball snow that clumps together into a ball well. In order for this to happen there has to be a layer of warm air in the atmosphere between the clouds and the ground for the snowflakes to fall through. Otherwise the snowflakes will not combine and they will stay relatively small and powdery.
Snow requires the air in the atmosphere to be below freezing (0oC or 32oF), but the air near the ground surface does not need to be at freezing. In order for snow to accumulate, the ground needs to be less than 41oF. Snowflakes absorb the heat from the environment around them when they melt, which in turn cools the air, and if this happens enough it can cool the air to 32oF which then stops the melting and the snow can then accumulate. This kind of condition also forms snowball snow because of the melting and sticking of the snowflakes.
After a snowfall the environment is quieter. Most of the space within snow is trapped air, and these air pockets absorb sound, which is what creates the hushed landscape. The more air space within the snow the more sound is absorbed. You might think that the large clumpy snow would absorb more sound but it is actually the powdery snow that absorbs more. This is because the powdery snow is not sticking to itself as much so there is actually more air space between them overall.
There are many signs in our environment that clue us in to what is happening around us. Even a simple little snowflake has a story to tell. Whether a snowflake is large or small, if it clumps into a snowball or is light and powdery, tells us what is going on in the air around and above us. Snow even has the ability to change the temperature of the atmosphere once it has fallen to the ground. When it comes to snow, moisture is the most important variable, which is why even in some cold places it still doesn't snow if the air is too dry. Even in parts of antarctica. Next time it snows, pay attention to what the snowflakes look like, and see if you can predict if it will be powdery snow or snowball snow, and enjoy the peace and quiet the snow provides.