Physics drop level 37 archive#

The absorption is preferential: More red light is absorbed than blue. The observer sees the light coming back from the near surface layers after it has been scattered or bounced off other snow grains only a few times, and it still appears white. That is, it must keep scattering and not be absorbed. If light travels over any distance, it must survive many such scattering events. As light waves travel into the snow or ice, the ice grains scatter a large amount of light.

Deep snow tends to absorb red light, reflecting the blue tints often seen in snow. Snow most frequently appears white, but deep snow can act as a filter, absorbing more of one color and less of another. How much sunlight the snowpack reflects to the atmosphere is characterized as snow's albedo. Clean snow, however, reflects most of the visible sunlight, creating a white appearance. Most natural materials absorb some sunlight, which gives them their color. Most all the visible light striking the snow or ice surface is reflected back without any particular preference for a single color. Generally, snow and ice present us with a uniformly white appearance. Over the winter season, the snowpack typically accumulates and develops a complex layered structure made up of a variety of snow grains, reflecting the weather and climate conditions prevailing at the time of deposition as well as changes within the snow cover over time. If snow persists on the ground, the texture, size, and shape of individual grains will change even while the snow temperature remains below freezing, or they may melt and refreeze over time, and will eventually become compressed by subsequent snowfalls. After a snowfall, snow may melt or evaporate, or it may persist for long periods. For example, when a snowfall is accompanied by strong winds, the snow crystals are broken into smaller fragments that can become more densely packed. The character of the snow surface after a snowfall depends on the original form of the crystals and on the weather conditions present when the snow fell.

Credit: Rich Herrmann/Flickr Snow on the ground The sun emerges after heavy snow hit Mount Vernon, Iowa. As weather conditions change, the snowpack can change as well, and this affects the characteristics of the snow. Snow is an accumulation of packed ice crystals, and the condition of the snowpack determines a variety of qualities, such as color, temperature, and water equivalent. As a result, this extremely cold region receives little snow. The Dry Valleys are quite cold but have very low humidity, and strong winds help wick any remaining moisture from the air. Antarctica's Dry Valleys, for instance, form the largest ice-free portion of the continent. It is true, however, that most heavy snowfalls occur when there is relatively warm air near the ground-typically -9☌ (15☏) or warmer-since warmer air can hold more water vapor.īecause snow formation requires moisture, very cold but very dry areas may rarely receive snow. Snow can occur even at incredibly low temperatures, as long as there is some source of moisture and some way to lift or cool the air. While it can be too warm to snow, it cannot be too cold to snow. As a general rule, though, snow will not form if the ground temperature is at least 5☌ (41☏). In this case, snowflakes will begin to melt as they reach this higher temperature layer the melting creates evaporative cooling, which cools the air immediately around the snowflake. However, the snow can still reach the ground when the ground temperature is above freezing if the conditions are just right. If the ground temperature is at or below freezing, the snow will reach the ground. Snow forms when the atmospheric temperature is at or below freezing (0☌ or 32☏). Snowstorms also rely heavily on temperature, but not necessarily the temperature we feel on the ground. Exchange for Observations and Local Knowledge of the Arctic (ELOKA)įor snow to fall, moisture must be present in the atmosphere.

Physics drop level 37 archive#

NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC).Greenland Today & Antarctic Ice Sheet Today.