Investigation of climate change effect on Temperature, Rainfall and intensity-duration-frequency Curves in Arid Areas (Case Study: Tehran-Karaj Basin)

the required information from the Mehrabad synoptic station in the Tehran-Karaj area of Tehran and Alborz provinces was prepared and then the parameters of rainfall, maximum temperature and minimum temperature were calculated by the SDSM scale scaling model under the new meteorological scenarios (AR5) and the CanESM2 general circulation model.Then, according to the outputs of the model, intensity, duration and frequency curves were extracted in different return periods for observation periods (1986-2018) and future (2051-2020 and 2051-2080).The results showed that although the winter and summer rainfall in the periods (2051-2021) and (2051-2020) in all three scenarios increased, the total annual precipitation would decrease for all three scenarios and in both periods (6.17 %, 8.02% and 8.48% respectively for scenarios of 2.6, 4.5 and 8.5, for the period 2021-2020 and 9.43, 7.98 and 8.56% during the period 2080-2080).Despite the fact that the average annual temperature does not show any significant changes compared to the observation period, the study of temperature data trends in different scenarios suggests an upward trend of the average annual temperature in predicted periods.Also, rainfall intensity in the periods 2021-2020 and 2080-2080 will decrease in all three scenarios: 2.6, 4.5 and 8.5 compared to the observation period (1986-2018). So that In the statistical period 2021-2050scenario 2.6 and In the statistical period 2051-2080, scenario 4.5, will have the highest reduction in rainfall compared to the observation period.