Simulation of precipitation and water flow as climatic parameters in Tehran province under CanESM2 model (based on an adaptation of SPI and SSI drought indices)

In the present study, to monitor droughts, the RCP4.5 scenario of the CanESM2 model of the Fifth IPCC Report and the most appropriate distribution functions of drought indicators were used to assess the current climate change and drought conditions in the present and future. Since the drought in an area can be affected by various climatic parameters, in this study, in addition to using SPI as a practical index, the important SSI index was also used to assess drought.

In the present study, the following steps were performed to monitor, evaluate, and inform the occurrence of droughts in Tehran province.
1.Quality control of precipitation and  water flow parameters during the period 1986-2018
2.Prediction of these parameters during the period 2020-2050 based on daily output data of CanESM2 model under the RCP4.5 scenario using SDSM model
3.Selecting the most appropriate distribution function with time series for both SPI and SSI index
4.Drought detection and simulation using SPI and SSI drought characteristics during the next period (2050-2050).

The results for future showed that Sharifabad station has the highest drought index (-2.74) based on SSI, and according to SPI, the highest drought index (-2.17) is for Latian station. It should be noted that the matching of the two indicators at Namroud and Latian stations was also studied and the results showed that the difference in the numerical values of these two quantities did not fit well for a 5 year period.