In the CRBasic programming language used by the data logger in the ET107 station, there is a programming instruction named ETsz. This instruction uses the short reference ASCE Standardized Reference Evapotranspiration equation. The outputs of the instruction are water loss in millimeters and the calculated clear sky solar radiation value for the site in MJ m-2. The inputs for the equation are temperature in Celsius, the relative humidity, the wind speed in meters per second (m s-1), and the solar radiation in total MegaJoules per meter squared (MJ m-2). The optimal interval for this calculation is hourly.