Climate Change Impact on Reference Evapotranspiration, Precipitation Deficit and Vapor Pressure Deficit in Urmia

Climate change via variations in temperature pattern، precipitation and other climate variables patterns affects all the hydrologic processes. One of the main consequences of the climate change is its impacts on agricultural water use، which can cause serious challenges for water resources management. The purpose of this research was to investigate the global warming impacts on reference evapotranspiration، precipitation deficit (PD) and vapor pressure deficit (VPD) in Urmia synoptic station. To achieve this goal، using the HadCM3 global circulation model and LARS-WG5 weather generator، the minimum and maximum temperature and precipitation values for 2011-2030، 2046-2065 and 2080-2099 periods based on A1B، A2 and B1 scenarios were simulated. Then، using the forecasted parameters، the reference evapotranspiration، PD and VPD were calculated and compared with the corresponding base data (1971-2010). The results show that in each of the three periods the precipitation in the spring will be decreased but the autumn precipitation will be increased in comparison with the base period. Meanwhile، the maximum event of the precipitation will be shifted from the spring season in the base period to the autumn season in 2090. Moreover، similar to air temperature، the reference evapotranspiration، PD and VPD will be increased in 2090 and such increment will be more in the warm months than the cold months. The amounts of these parameters’ increments in the A2 scenario are more than those in the A1B scenario and also in the A1B scenario are more than those in the B1 scenario.