ASSESSMENT OF THE METEOROLOGICAL PARAMETERS EFFECTS ON THE DAILY PENMAN REFERENCE CROP EVAPOTRANSPIRATION

The FAO-24 corrected Penman method has gained acceptance as a standard method of estimating daily reference crop evapotranspiration (ET_r) as it takes into account almost all the factors which are known to influence ET_r. However, the Penman-Monteith method is currently favoured by the FAO over the FAO-24 corrected Penman method.
In this paper, daily ET_r estimated using the Penman-Monteith and FAO-24 corrected Penman methods with daily meteorological data from an Automatic Weather Station (AWS) which is sited at Piperia (Northern Greece) are compared.
The analysis indicates that the FAO-24 corrected Penman ET_r estimates are higher than the Penman-Monteith estimates and the difference is 33% in the estimate of two year ET_r. Although theoretically sound the FAO-24 corrected Penman and Penman-Monteith methods become increasingly empirical when net radiation (R_n) has to be estimated.
In this paper, to assess the R_n effects on the FAO-24 corrected Penman and Penman-Monteith estimates of daily ET_r for the Piperia AWS site comparisons are carried out using measured R_n data and R_n values computed by an empirical relationship with different empirical values.
It is found that the different empirical values used to estimate R_n give different daily ET_r estimates being higher than the measured R_n data for the two methods.

II International Symposium on Irrigation of Horticultural Crops

D.M. Papamichail, G.A. Terzidis

FAO-24 corrected Penman, Penman-Monteith, Automatic Weather Station, reference crop evapotranspiration

https://doi.org/10.17660/ActaHortic.1997.449.40