• PENMAN-MONTEITH will calculate potential evapotranspiration (PET) by the Penman-Monteith method. The calculation will be for the reference crop, i.e., clipped grass of 0.12 m height.

  • For the reference crop, the internal (stomatal) resistance (s/m) is equal to 200/L, where L is the leaf-area index, L = 24 hc, with hc = 0.12 m.

  • The external (aerodynamic) resistance (s/m) is equal to 208/v2, where v2 is the wind velocity at 2-m depth.

  • The input data is [mean monthly] temperature (degrees Celsius), the given month, [mean monthly] net radiation (cal/cm2/day), relative humidity (%), wind velocity at 2-m depth (km/day), and atmospheric pressure (mb).

  • The output data is daily PET (cm) and monthly PET (cm).

  • Allowable input data ranges::   Temperature is restricted in the range 0-40 degree Celsius; [mean monthly] net radiation in the range 0-1000 cal/cm2/day; relative humidity in the range 0-100%; wind velocity at 2-m depth in the range 0-1000 km/day; atmospheric pressure in the range 500-1013.2 mb. Input values outside of these ranges will cause the respective value to reset to the closest limit [Example: entering 1100 for wind velocity will cause its value to reset to 1000].

Click  -here- to view a sample data set.

RUN!

DISCLAIMER: The developer makes no warranties, expressed or implied, concerning the accuracy, completeness, reliability, or suitability of this program for any one particular purpose. It is understood that the user proceeds at his/her own risk.