Reflected Shortwave Solar Radiation
regions on this map reflect the suns energy back into
space: The white or beige areas show sunlight reflecting from
Africas Sahara Desert, as well as from high clouds over
the tropical oceans, Amazonia, and tropical Africa. On the
other hand, darker areas show sunlight penetrating the atmosphere
in the cloud-free areas of the oceans.
This view illustrates the earths reflectivity, or albedo.
The earths average albedo is about .3, which means that
the earth reflects about 30% of the sunlight that hits it
overall. However, different areas reflect different amounts
of energy: Clouds, deserts, and snow have high albedos and
reflect away most of the sunlight they receive; vegetation
and water, with lower albedos, absorb more of that energy.
These processes form the earths energy budgetand
they are key in determining climate: Sunlight that penetrates
the atmosphere heats the earths surface. Some of that
heat is trapped by the atmosphere, keeping the planet warm.
Thats why studying the balance between absorption and
reflection is a fundamental step in understanding climate.