What is ETo?
Evapotranspiration (ET) is the combination of evaporation of water from the soil and plant surfaces and water transpired due to plant growth. ETo is evapotranspiration from standardized vegetation surfaces (grass or alfalfa) with known biophysical characteristics. A standard vegetation surface is required because different plants have different biophysical characteristics and it is not practical to formulate equations for each type of planting. The standard reference surface for CIMIS ETo estimation is well-irrigated, clipped grass.
