Solar Energy and the Atmosphere

Radiation Earth’s atmosphere is heated by the transfer of energy from the sun. Is all forms of energy that travel through space as waves RADIATION Travels as waves at high speed 300,000 km/s

Electromagnetic spectrum Various types of radiation differ in their wavelengths The wavelengths of ultra violet rays, x-rays and gamma rays are shorter than those of visible light VISIBLE LIGHT

How does the atmosphere affect solar radiation? 20 % is absorbed by clouds, dust and gases Solar radiation enters the atmosphere 50% absorbed by Earth’s surface 30% reflected by clouds, dust, air and Earth’s surface back into space

Ozone is formed as ultraviolet rays are absorbed in the stratosphere and act upon the existing oxygen molecules.

SCATTERING- particles and gas molecules in the atmosphere reflect and bend rays. Sends some radiation back into space The remaining continues towards Earth’s surface Scattering is what makes the sky appear blue and the sun appear red at sunset REFLECTION- amount reflected depends on the characteristics of the material on which the solar radiation falls The fraction reflected by a particular surface is called ALBEDO 30% of solar energy that reaches Earth’s atmosphere is either reflected or scattered, Earth has an albedo of 0.3

Absorption Radiation that is not reflected is absorbed by rocks, soil, water and other surface materials. Infrared rays and visible light heat the Earth’s surface The heated materials convert the energy into infrared rays and reemit the energy at those wavelengths. The gas molecules in the atmosphere absorb the infrared rays heating the lower atmosphere and keeping the Earth warmer than if there were no atmosphere Sometimes warm air bends light rays to produce a MIRAGE

Conduction The transfer of energy as heat from one substance to another by DIRECT contact Air is a poor conductor because the molecules are so far apart. So, conduction only heats the lowest few cm of the atmosphere where air is in DIRECT contact with the Earth’s surface

Convection The process which air or other matter rises and sinks because of differences in temperature Heated air is less dense so the colder air pushes it up Cooler air becomes warmer, repeating the cycle. This cycle warms Earth’s atmosphere Atmospheric pressure differences between warm and cold air creates wind.