Reference Evapotranspiration (ETo)

CIMIS uses the Modified Penman-Monteith Equation to calculate the reference evapotranspiration rate of grass.  CIMIS uses hourly inputs generated by the weather stations using the following variables: air temperature, relative humidity, wind speed, vapor pressure, elevation of station above sea level and calculated net radiation.

To learn more about meteorological factors determining ET visit - Crop evapotranspiration - Guidelines for computing     crop water requirements - FAO Irrigation and drainage paper 56

The equation for estimating ETo is complex and could be viewed in detail at the following sites: .

To understand Evapotranspiration further visit these sites:, - from UC Davis Biometeorology