Albedo is a word describing the portion of the sun’s radiation reflected from a surface. Albedo is also an important element of our weather.

Most sunlight passes directly through air with relatively little absorption. The reason it is usually warmer in the afternoon than at night is because of solar radiation heating the ground and the ground then heating the air via convection. Snow-covered ground has an albedo between 0.40 and 0.90, meaning snow cover reflects between 40 and 90 percent of the radiation (light and heat) coming in from the sun.

This is why a snow-covered field is so bright on a sunny day and also part of why it is so cold in winter. Dark, wet soil, on the other hand, has an albedo near 0, meaning it absorbs almost all the solar radiation it receives. This is why temperatures above 50 degrees are rare in spring until most of the winter snow melts.