عنوان مقاله [English]
نویسندگان [English]چکیده [English]
In this study sensitivity of reference crop evapotranspiration (ETo) to the changes in meteorological parameters at two weather stations namely Sanandaj and Sabzevar were analyzed. For this purpose monthly data of meteorological parameters were used in the period 1964-2005. The amount of each meteorological parameter including mean air temperature, wind speed, actual vapor pressure and net radiation was changed in the range of ±20% and the corresponding change in ETo was calculated. This was accomplished either for the individual or for the combination of the parameters. Results showed that at both stations the maximum sensitivity of ETo belonged to Tmean, at both annual and monthly time scales. However, the less sensitive parameter in both time scales was actual vapor presuure. At the annual time scale, 20% increase in Tmean increased ETo for about 11.23% and 12.68% at Sanandaj and Sabzevar stations, respectively. However, 20% increase in ea decreased ETo for about 3.29% and 3.59% respectively at the same stations. At monthly time scale, Sanandaj ETo was less sensitive to weather parameters variations than that of Sabzevar station. In general, it could be concluded that at both stations the most influential parameter on ETo was the mean air temperature.