Ask Ms. Scientist: Winter cold & black ice
Why are some winters worse than others?
One reason why we have different winters from year to year is two special climate patterns: El Niño and La Niña. These two climate patterns alternate with each other, often year by year. El Niño and La Niña are defined by how they affect the average ocean temperatures around the world; El Niño raises ocean temperatures, while La Niña lowers them. However, their biggest impact on us is how they affect our weather and amount of rainfall. In the northern U.S., La Niña episodes mean that we get a lot more precipitation than usual, meaning if La Niña happens in the winter, we get a lot of snow. Episodes of El Niño don’t make a huge difference in the north where we are, but they make the winters in the southern portion of the U.S. a lot wetter and colder. So, be sure to bundle up this winter and stay warm, regardless of the episode we're in.
What is black ice?
Winter is officially here and it brought along slippery roads and sidewalks coated in ice sheets. But, certain patches of ice are more slippery than others. These are often referred to as “black ice” patches. However, what exactly is black ice, and what makes it so much more slippery than other ice patches? Here is some helpful information to help you identify the slippery spots when walking to class this week. To start, black ice is not actually black. The name comes from the typical color of the road that the black ice patches are found on. The ice freezes over a relatively dry spot on the sidewalk or road making it hard to identify without much snow around. The ice patch freezes clear, which makes it appear the color of the road. It is often caused by a light drizzle of rain or icy rain, and the thin patch is nearly invisible. Automobile exhaust can also be a causing factor. Salt can help to alleviate black ice, but once the temperature dips below zero degree Fahrenheit, salt only adds to the problem. Be careful on those slick sidewalks this winter.