Weather Whys; Earth's Energy Balance

This is weather wise. The Earth and its atmosphere are in a state of energy balance. That means the energy coming in is equal to the energy going out. The planet receives energy from the sun and some of it is reflected or re-radiated back into space. In fact, over the entire Earth, an average of 20 percent of the incoming solar radiation is repelled by clouds alone. Scientists say the Earth and its atmosphere have an average albedo of about 31 percent. The albedo of a substance is a measure of how much solar radiation will be reflected by it rather than absorbed. Let's say the sun sends 100 units of energy toward the Earth. And we could expect about 80 of those units to make it past the tops of the clouds. About six of the remaining units are scattered by the atmosphere, and another 19 are absorbed by the atmosphere and the clouds.

Then, even as the remaining 55 units hit the ground, four of them are sent right back where they came from by reflection from the Earth's surface. Snow and white sand are the main reflectors. In fact, fresh white snow can reflect as much as 95 percent of the radiation that hits it. So of the 100 hypothetical units the sun sent to Earth, only about half of them actually make it to the ground. In other words, just a little over 50 percent of the sun's radiation is normally absorbed by the Earth itself. That energy is re-emitted in various ways, which keep the system in balance. How do scientists know that's true? As they say, if the incoming and outgoing radiation aren't in balance, the Earth would be increasing or decreasing in temperature. But since the average temperature is very nearly constant, they know the radiation must be in balance. Whether wise is a production of KGOU radio and the Center for Analysis and Prediction of Storms at the University of Oklahoma.

I'm Drew Barlow.