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Category Archives: Phenomena
Why don’t we see rainbows at noon?
The classic rainbow is a single, brightly colored arc. Red is the outermost color of this arc, and violet is always innermost.
On occasion, you may see two rainbows at once. The lower rainbow is the primary rainbow, and the higher, more faintly colored arc is the secondary rainbow. The color sequence of the secondary rainbow is opposite to the primary; red is on the inside of the arc and violet is on the outside. Continue reading
What causes urban flooding?
Urban flooding occurs when water flows into an urban region faster than it can be absorbed into the soil or moved to and stored in a lake or reservoir. It can be caused by flash flooding, coastal flooding, river floods or rapid snow melt.
On Tuesday, the Madison area experienced urban flooding caused by an intense rainfall. On that day, a daily record rainfall of 1.46 inches fell at Dane County Regional Airport, breaking the city’s previous May 27 record of 1.27 inches. The city sewage system and draining canals did not have the necessary capacity to drain away the large amounts of rain that fell in a short period of time. Continue reading
What was that column of light extending above the setting sun?
A vertical shaft of light extending above a setting or rising sun is called a sun pillar. You could have seen this optical phenomenon if you were looking at the sunset on Jan. 18.
While sun pillars look like vertical beams of light projected above the sun, they are actually a collection of reflections of millions of ice crystals floating in the atmosphere. Continue reading
How do the Yahara lakes freeze?
Lakes freeze from the surface downward to the lake bottom. Ice floats because it is less dense than liquid water.
The density of liquid water depends on the water temperature. The density of water is highest at a temperature of about 40 degrees Fahrenheit. So, why is that important? Continue reading
What was that dashed line in the sky on Nov. 3?
If you watch jets fly high above, you may notice that sometimes white clouds trail them. These condensation trails are called contrails. Most clouds form as air rises. Contrails form by a mixing process that is similar to the cloud you see when you exhale and “see your breath”. Continue reading
