Sunday, November 25, 2018

Greenhouse Effect and Radiative Heat Transfer

Most of the heat that warms our biosphere comes to us in the form of Infrared Radiation (IR) that is easily absorbed by greenhouse gases as it both enters our atmosphere and as it is reradiated from the surface of the planet after being absorbed and reradiated.

A portion of visible light is, also, transformed into kinetic energy (heat) after it strikes the surface of our planet. This kinetic energy generates and re-emits long waved IR radiation in all directions. That which is radiated outwards is easily reabsorbed by the larger gaseous molecules in the atmosphere. As these greenhouse gas molecules increase their rate of kinetic vibration (heat), they re-emit IR in all directions 

Note: Long waved IR is more easily absorbed than shorter waves visible light. 
Also, add the incoming IR from the sun to the amount of IR and visible light that has already struck the Earth’s surface as is being reradiated as IR, and you soon find yourself grateful that the atmospheric greenhouse effect isn’t any stronger than it already is (though this is gradually changing).

Note: Thermal radiation is one of the three principal mechanisms of heat transfer. It entails the emission of a spectrum of electromagnetic radiation due to an object's temperature. Other mechanisms are convection and conduction. The interplay of energy exchange by thermal radiation is characterized by the following equation...

Read “interchange of Energy” section in Thermal Radiation: