Weather Whys; Snow Color

This is weather wise. New fallen snow is usually as white as white can be. But like many weather phenomena, there have been exceptions to the rule. For example, in rare instances, snowflakes can be yellow, brown, or even red. That happens because of the way the snowflakes form in the first place. It's very difficult for water droplets to become ice crystals all by themselves. In fact, because it's so difficult, there are often a lot of water droplets in the atmosphere that actually have temperatures below freezing. Those sub-freezing droplets are said to be super cool. But when a special kind of particle called a freezing nucleus comes along and contacts one of those super cool droplets, an ice crystal can form rapidly. Those freezing nuclei form the core of most ice particles in the atmosphere. Now scientists know that minuscule dust particles are some of the best freezing nuclei available,

and occasionally that dust can give snowflakes a brownish appearance. Also, a late spring snowfall can sweep large quantities of pollen out of the air, and that can lead to snow covers that take on a yellowish appearance. But there are even some areas of the globe that can experience more startling colors. For instance, there are numerous tiny plants that grow in fallen snow, and as a result produce a snowy blanket of green or even red. So there's more to snow than usually meets the eye, and the graying slush found on city streets several days after a snowfall isn't the only color option. If you'd like to know what you think of WeatherWise, please write us at WeatherWise KGOU Radio, the University of Oklahoma, Norman, Oklahoma, 73019-0250. For WeatherWise, I'm Drew Barlow.