Future projection for extreme indices of precipitation and temperature over the period 2026-2100 based on the output of CMIP6 models (Case study: Mashhad)

In this research, 11 extreme climatic indicators out of 27 indices defined by the ETCCDI task team have been studied. The capability of the CMIP6 model in the simulation of selected historical climatic extreme indices has been evaluated. The observation and future periods are considered to be 1989-2014 and the three 25-year periods of 2026-2050, 2051-2075, and 2076-2100, respectively. Three Earth System Models (ESM) including ACCESS-CM2, MIROC6, and MRI-ESM2-0 were evaluated for this study. CMHyd and Rclimdex software are used for downscaling and estimating the daily mean and extremes of precipitation and temperature under three SSP scenarios of SSP1-2.6, SSP2-4.5, and SSP5-8.5. The results showed that among the three ESM models, the ACCESS-CM2 model has a better capability when compared to other models in simulating historical extremes of precipitation and temperature, so, it was selected as the appropriate model for future projection. The results showed that, in all SSP scenarios and over three near, mid, and far futures periods, the cold night index (TN10p) has decreasing trend and the warm nights (TN90p) percentage has a significant increasing trend at 95% confidence level. The number of Summer days (SU25) has an increasing trend in all SSP scenarios in the near future at a 90% confidence level. It has also increasing trend in mid future under SSP2-4.5 and SSP5-8.5 and far future in SSP1-2.6. Awareness of the future perspective of extreme rainfall indices due to their impact on soil erosion can be used in soil management planning and also Information on rainfall and temperature extreme events can be used in water resources management planning.