Super Coooool Snow
The average annual precipitation of highland tundras varies greatly, with most being greater than lowland tundras. Most or all of the precipitation in a highland tundra is in the form of snow.
Snow is made of transparent ice crystals (solid materials whose particles are arranged in a repeating pattern). These crystals are formed when water vapor in the air freezes. The process of a vapor changing directly to a solid without becoming a liquid is called sublimation. This occurs when water vapor condenses at temperatures below the freezing point. As snow crystals fall and collect on the ground, air becomes trapped among the crystals. Thus snow is puffed up with air, making it not only soft and fluffy but also larger in volume than the water it is made from. So when 1 inch (2.5 cm) of snow melts it will not produce 1 inch (2.5 cm) of water. A measurement for annual precipitation is a measurement of liquid water. For example, if snow is the only precipitation, and the average annual precipitation is 20 inches (50 cm), this annual precipitation measurement means that enough snow falls to equal 20 inches (50 cm) of rain.
Air is a good insulator, so it helps to keep heat from escaping. Because of the trapped air in snow, snow is a good insulator. In the tundra, snow acts like an insulating blanket that traps some of the heat given up by the ground. Ground covered by air-filled snow cools slowly because of the insulating snow. Thus when the air temperature is below freezing, 32°F (0°C), the ground covered by snow is warmer than the air above the snow. Many small tundra animals, such as shrews, gophers, and mice, live under layers of snow and remain active during the winter. These animals can breathe because the snow is so full of air. Plants also benefit from the warm temperatures due to snow covering. Above-ground plant parts can survive in the insulating snow. Animals living under the snow, as well as larger animals such as elk, mountain goats, and sheep, seek loose snow where they can uncover edible plants.
To measure the volume of melted snow.
- masking tape
- straight-sided transparent plastic drinking glass at least 5 inches (12.5 cm) tall
- metric ruler
- snow (shaved or finely crushed ice will work if snow is not available)
- Place a strip of tape down the outside of the drinking glass.
- Starting at the bottom of the tape strip, measure the height of the strip in centimeters. Write this measurement on the top of the strip of tape.
- Scrape the glass across the snow to fill it, then level the top of the snow in the glass by scraping the edge of the ruler across the mouth of the glass. Take care not to pack the snow in the cup. Fresh snow works best.
- Allow the filled glass to sit at room temperature until the snow melts.
- Mark the height of the water in the glass on the strip of tape. Measure this height in centimeters and write it on the tape. Compare the height of the snow to the height of the water it forms when melted.