Friday, 25 May, 2012

What is sleet? ENLARGE Photo: Generation X-Ray When precipitation droplets refreeze before hitting the ground, you get sleet. Sleet is translucent balls of ice that are frozen raindrops. The most common forms of precipitation are rain, snow, freezing rain, and sleet. In Wisconsin, precipitation usually begins as ice particles in a cloud. The temperature conditions [...]

Where does the water come from in Midwestern snow storms? ENLARGE Photo: NOAA/NASA GOES Project Water can travel a long way to dump onto the Midwest as snow. This picture shows the storm system that cause the massive February 2011 storm. Last week we were visited for the second time this winter by a sizable [...]

Do abundant snowstorms suggest global warming is not occurring? ENLARGE Graphic: Rutgers University Global Snow Lab This graphs shows the area of land covered by snow over the past few decades in North America. No. These storms are individual weather events, which cannot be used to support or refute climate trends. Which also means that [...]

Why does snow disappear? ENLARGE Photo: Amanda Graham Sublimation in action. When the snow builds up on my patio, it starts to evaporate after a few days, even though the temperature is still below freezing. On average, what percentage of our snowfall each year evaporates back to the air? The transition of water from the [...]

How do snow fences work? Photo: flickr via Wikimedia Commons, by John Talbot. Snow fence might not have helped here (Ottawa, Canada). Snow carried by wind can reduce visibility and cover roads. We cannot “switch off” the wind; but we can slow it with obstacles. Obstacles like trees and fences break wind into a swirl [...]

Is Madison, Wisconsin in a snow belt? What is the origin of the term? While the lakes around Madison provide many winter recreation activities, the local lakes do not yield a snow belt. Map by Pierre cb We refer to agricultural regions in the United States as ‘belts’, such as the cotton belt and wheat [...]

What is ‘black ice’? The term ‘black ice’ refers to either a new layer of transparent ice on water, which allows us to see the deep water below, or a layer of clear ice on a roadway, which makes for hazardous driving. In both cases, the ice is transparent, not black, and so it shows [...]

I thought I heard thunder during a snowstorm. Is that possible? Yes. A storm that includes any occurrence of thunder with snow is called a thundersnow event or thunder snowstorm. Lightning and thunder go together; you can’t have one without the other. Thunder is generated when the lightning heats the air five times as hot [...]

Why does snow sometimes sparkle? Photo of snow in west Sierra Nevada by Itrovert Sometimes on a sunny day, freshly fallen snow may appear to sparkle or glitter. This happens because when light hits an object light, it can be absorbed, in which case the object is heated; transmitted, in which case light passes through [...]

Snow can make both ‘squeaky’ and ‘crunchy’ sounds. Snow is a mixture of ice crystals, liquid water and air, and the sound it makes when you walk on it depends on the proportions of this mixture.