poster - International Conference of Agricultural Engineering

4. Conclusions
Sensitivity coefficients of reference crop evapotranspiration to mean air temperature, net
radiation, Vapor pressure deficit and wind speed were calculated and analyzed by ASCE-
Penman-Monteith method in Kerman, Baft, Bam and Jiroft (Southeast of Iran) using daily
dataset. The study results show that on the whole, net radiation is the most and air
temperature is the least sensitive meteorological factors for most of measurement locations.
Our results are not directly comparable to those of other sensitivity analyses since the
predictions for vegetation surfaces (Beven, 1979; Saxton, 1975) or open-water surfaces (Mc
Cuen, 1974) were considered in the other available papers. However, all studies (Mc Cuen,
1974; Saxton, 1975; Coleman and DeCoursey, 1976; Beven, 1979) showed that potential
evaporation or evapotranspiration was much more sensitive to radiation and humidity.
Therefore, accurate estimation of evapotranspiration rates in all the measurement stations
depends primarily on the solar radiation. For highest S Rn (0.88), increase of 10% in net
radiation may cause increase of 8.8% in ET o . We can conclude that vapor pressure deficit is
the second controlling factor to ET o among the climate variables. The results provide a new
approach for ET o estimation in Kerman province, and also can be used as a theoretical basis
for future research on the response of reference evapotranspiration to climate change.
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