17.2 – Heating the atmosphere – Part II

Do Now What percentage of incoming solar radiation is reflected by clouds?

Do Now What percentage of incoming solar radiation is reflected by clouds? 20%

Key Words Transmit Efficiently

Vocab Words Reflection Scattering Greenhouse Effect

Solar Radiation When radiation strikes an object, there usually are three different results. Some energy is absorbed by the object. Substances such as water and air are transparent to certain wavelengths of radiation. Some radiation may bounce off the object without being absorbed or transmitted.

Reflection and Scattering Reflection occurs when light bounces off an object. Reflection radiation has the same intensity as incident radiation. Scattering produces a larger number of weaker rays that travel in different directions.

Scattering Spreads light both forward and backward More energy is spent going forward. About 30% of solar energy is reflected back to space, mostly by scattering. Small dust particles and gas molecules in the atmosphere cause the scattering. Scattering also accounts for the brightness and even the blue color of daytime sky.

Absorption About 50 percent of the solar energy that strikes the top of the atmosphere reaches Earth’s surface and is absorbed. The greenhouse effect is the heating of Earth’s surface and atmosphere from solar radiation being absorbed and emitted by the atmosphere, mainly by water vapor and carbon dioxide.

Group Activity Copy and label the picture page 486 (Figure 12), make sure to include all percentages!!