A MEASUREMENT BASED SENSITIVITY ANALYSIS OF THE PENMAN-MONTEITH ACTUAL EVAPOTRANSPIRATION MODEL FOR CROPS OF DIFFERENT HEIGHT AND IN CONTRASTING WATER STATUS
G. Rana et N. Katerji, A MEASUREMENT BASED SENSITIVITY ANALYSIS OF THE PENMAN-MONTEITH ACTUAL EVAPOTRANSPIRATION MODEL FOR CROPS OF DIFFERENT HEIGHT AND IN CONTRASTING WATER STATUS, Theoretical and applied climatology, 60(1-4), 1998, pp. 141-149
This paper presents a study of the sensibility of the Penman-Monteith
evapotranspiration model to climatic (available energy and vapour pres
sure deficit) and parametric (aerodynamic and canopy resistances, r(a)
and r(c) respectively) factors in a semi-arid climate, for crops in c
ontrasting water status (well irrigated and under water stress) and of
different heights. Three experiments were carried out in southern Ita
ly on reference grass (approximate to 0.1 m), grain sorghum (approxima
te to 1 m) and sweet sorghum (approximate to 3 m). For this analysis t
he sensitivity coefficients, taken as hourly means, were evaluated dur
ing the growth season when the crops completely covered the soil. The
relative errors on evapotranspiration were also evaluated for r(a) and
r(c). The results showed that, for reference grass, available energy
and aerodynamic resistance play a major role. For crops under water st
ress the most important term to evaluate is canopy resistance. For a t
all crop, as sweet sorghum, the role of the vapour pressure deficit is
fundamental, both when the crop is in good water status and under wat
er stress.