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Category Archives: Meteorology
Are the number of thunderstorms in Wisconsin decreasing?
This question comes from one of our readers, based on casual observation. It is always good to get data and analyze such a generalization to find the best answer. So, we turned to the Wisconsin State Climatology Office.
The National Weather Service records the number of thunderstorm days at several sites across the U.S. A thunderstorm day is when thunder or lightning is detected at least once during the day. Since the mid-1990s, the nation’s primary surface weather observation network is the Automated Surface Observing Systems, or ASOS program, which has essentially replaced human observers. Continue reading
Category: Climate, Meteorology, Severe Weather
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Why was the sun so red this past week?
Light is a form of electromagnetic energy that does not need matter to propagate. We can characterize this energy by its wavelength, which is the distance along a wave from one crest to another. Our eyes are sensitive to light with wavelengths between approximately 0.4 to 0.7 microns. Blue colors have shorter wavelengths, while red colors have longer ones.
When light interacts with particles suspended in air, it can be scattered or absorbed. Energy that is scattered causes a change in direction of the light path. The amount of light that is being scattered is a function of the size of the particle relative to the wavelength of the light falling on the particle. While all colors are scattered by air molecules, violet and blue are scattered most. The sky looks blue, not violet, because our eyes are more sensitive to blue light. Continue reading
Category: Meteorology, Phenomena, Weather Dangers
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Can record high and low temperatures help define regional definitions of seasons?
Though it now seems to be fully in swing, the spring has sure seemed delayed in coming this year in southern Wisconsin. This made us wonder if there might be a more refined, and local, way to think about the calendar-day boundaries of the seasons.
In research undertaken to write a recent column, we catalogued Madison’s record high and low temperature data for each calendar day employing data that went back to 1939. An interesting partition of the full year resulted from this simple analysis. Continue reading
Category: Climate, Meteorology, Seasons
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What are gravity waves?
Picture a rock thrown into a lake on a calm day. That is an excellent example of what a gravity wave looks like.
Ripples migrate from where the rock hits the water, causing an up and down motion along the water’s surface. As we get farther away from the point where the rock hit the water, the waves dampen, becoming less defined. Continue reading
What causes April showers?
The weather this past week in Madison has been very interesting.
On at least three occasions we experienced a mix of precipitation types — with snow, hail, graupel and rain in various combinations. Continue reading
