Section 2: Atmosphere Energy Transfer

Almost all of the energy in Earth’s atmosphere comes from the sun.  Radiation is the transfer of energy by electromagnetic waves. This is energy that can travel through space.  About 99% of radiant energy from the sun that reaches Earth is either visible light, infrared radiation, or ultraviolet light.  The majority of sunlight is visible light in the form of a mixture of all the colors you see in the rainbow.  Infrared radiation is a form of energy with wavelengths longer than visible light, and it is not visible but can be felt as heat.  The sun also gives off ultraviolet light, which has short wavelengths and can break chemical bonds.  As sunlight enters the atmosphere, it is converted to infrared radiation and is trapped by gases in the air called greenhouse gases. This is a natural process to regulate temperature on Earth, which is one of the most important elements of weather.  These gases create a blanket around Earth, which is called the greenhouse effect.

There are three types of thermal energy transfer that work together to heat the troposphere: radiation, conduction, and convection.  Radiation is the direct transfer of energy by electromagnetic waves.  Conduction is the transfer of thermal energy by contact particles of matter.  It occurs when the atmosphere touches Earth.  Convection is the transfer of thermal energy by movement of particles within matter. This is how air currents are heated.  Convection currents are formed when less dense air that is warmed by Earth’s surface is forced to rise by the downward movement of cooler, denser air.

Stability refers to whether circulating air motions will be strong or weak.  Stable conditions are caused by weak circulating air; unstable conditions are caused by strong moving air, usually producing thunderstorms.  Temperature inversion takes place in the troposphere when the temperature increases as altitude increases.  Trapped pollution can be the result of temperature inversion.

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