Global radiation, temperature and relative humidity
were used for the calculation of net radiation data,
obtained by applying a model derived from Brutsaert’s
equation (Ortega-Farias et al., 2000). This model was
chosen as it was set up for use at an hourly time step
and in Mediterranean conditions. The values obtained
were considered as sufficiently representatives of net
radiation above the canopy, meaning that there was
only vegetation under the sensor. An interception
formula was applied to calculate the below-canopy
values (Norman and Campbell, 1983). Data recorded
in field during the 2003 season were used for the
verification of the entire procedure.