Evapotranspiration Condition in Yazd Station under Uncertainties of Different GHG Emission Scenarios and ET Estimation Models

Drought as a prevalent phenomenon has seriously affect water and agricultural resources of Iran, especially in recent decade. Evapotranspiration (ET) is an important climatic factor of drought occurrence that would change as a result of global climate change. In this regard, uncertainties that almost arise in ET simulation approaches would be important and however, would affect ET projection results in upcoming decades. This research investigates uncertainties of ET simulation results under different Green House Gas (GHG) emission scenarios and different ET estimation models in Yazd meteorological station. For this purpose, reference ET was first determined using historical data of studied station through Hargerives-Samani and Thornthwaite approaches. Then, simulated daily Tmin and Tmax data of HadCM3 model that were resulted from GCM-runs based on the IPCC-SRES scenarios of A2 and B2 were used for projection of potential ET in 2010 to 2039 period, as well. Results of the study show increase of Tmin and Tmax in 2010 to 2039 compared with the historical period (1961-1990). Also the results indicate that potential ET of Thornthwaite approach would have an increase of about 0.4 mm per day in the future three decades, while the projected ET of Hargerives-Samani approach would not be increased, significantly.