SIOUX FALLS, S.D. (KELO) — If you thought to yourself at any point that these last few nights have felt especially cold, you’d be right.
We all know just how warm the first week of November was, with several records either challenged or broken. The swing to the chillier side of the pendulum has been rough enough, but the last few nights have been especially cold.
We’ve had a perfect set-up for these colder nights, with three main ingredients in place: Clear skies, calm winds, and snow on the ground. To explain why this cools us down so much, let’s look at something called “Albedo”.
Albedo is a measure of how well or poorly a surface absorbs solar energy…or in this case heat…on a 0 to 1 scale. If a surface has an Albedo near 0, that means it absorbs this energy very effectively. An Albedo closer to one indicates the opposite. Bare ground, for example, has an Albedo of around 0.25. That means it reflects about 25% of the solar energy that comes down and absorbs the rest. Fresh snow, however, is a poor absorber of solar energy. With an Albedo of 0.9, that means snow reflects nearly 90% of the energy that comes down.
With no cloud cover in place to keep the warmth trapped at the surface, all that heat goes back into the atmosphere. The end result is a noticeably colder snow-covered night as opposed to a night with no snow.
Though we have one more rather cold night on the way tonight, there is change on the way. As our weather pattern nudges closer to more seasonable conditions, our snowpack will continue to fade away and overnight lows won’t fall as far down the thermometer.