Evaporation and Transpiration

EVAPORATION AND TRANSPIRATION are the two processes by which water is removed from the Earths atmosphere. Because it can sometimes be difficult to ascertain which one is occurring, the term evapo-transpiration [Page 399]is often used to describe the sum total of both processes. Evapotranspiration is an important part of the planet s hydrological cycle, and it is likely to change in a warming world.

Evaporation is the process of changing water from a liquid to a gaseous state. Water molecules are in motion, and if they generate enough speed and are going in the right direction, they essentially heat themselves to the equivalent of boiling, at which point, they have enough energy to escape the liquid state and pass into the atmosphere. Only a small percent ...