Projection of Precipitation and its Variability under the Climate Change Conditions in the Future Periods (Case Study: Tabriz)

In this research, projection of precipitation in the three distinct 20-years future periods (i.e. 2021-2040, 2041-2060, and 2061-2080) was performed using the LARS-WG6 statistical downscaling model. For this purpose, two scenarios of the IPCC fifth assessment report (namely RCP4.5 and RCP8.5) and MPI-ESM-MR general circulation model, which is known to be a CMIP5 coupled models were utilized. The precipitation trends were analyzed in the base and future periods using the Mann-Kendall method for both seasonal and annual time scales. Sen’s estimator method was used to estimate the slopes of trend lines. The results showed that winter precipitation will be increased during the three considered future periods. Moreover, in the spring and autumn, according to the RCP8.5 scenario, precipitation will be decreased in all future periods. The precipitation in December and January would be increased in all three future periods using both scenarios. March, July, September, and October will also experience a decline in precipitation in the three future periods, according to both scenarios. The mean annual precipitation in the future period of 2061-2080 would be decreased based on both scenarios. The highest reduction in precipitation would occur in the period 2061-2080 belonged to the RCP8.5 scenario in which the amount of reduction in mean annual precipitation is equal to 10.4%. In addition, based on the RCP4.5 scenario, the highest increase in the average annual precipitation during the future period of 2041-2060 was equal to 8.1%. There was no significant trend in precipitation series at 5% level. The slope of the trend lines in the base period and the future periods, based on the scenario RCP8.5, was found to be negative in all seasons. While in the future period, based on the RCP4.5 scenario, the trend line slope was positive for in all seasons.