The other two types refer to the calculation methods set out in p. 4 of the document “Sunshine duration –
Vuerich.pdf”. In particular:
- Step Algorithm (SA)
- Carpentras AKA Meteo-France Algorithm (MFA)
The first method requires the measurement of global radiation (averaged over one minute) and the angle of
elevation of the sun (§4.2.3.1).
Fig. 26 – Example of calculated measurement configuration of type "Sun visibility (Step Algorithm)”
The second, like the first, requires the measurement of global radiation and the angle of elevation of the sun
(§4.2.3.1) and the coefficients A and B, respectively set to the default values 0.73 and 0.06.
Fig. 27 - Example of calculated measurement configuration of type "Sun visibility (Meteo France)”
4.2.3.4 Penman-Monteith evapo-transpiration
The calculation of evapo-transpiration according to Penman-Monteith model is based on the original FAO
document available at http://www.fao.org/3/X0490E/x0490e06.htm. The calculated index is named ET0 and
refers to a land area with grass having specific characteristics. In this way the calculation is independent of
the type of crop present at the measuring site and provides comparable results to other sites with different
types of cultivation.
The FAO document shall specify the use of the following measured quantities:
• Temperature
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