Uncertainty Analyses of Future Rainfall and Temperature Conditions Over Ghara Sou River Basin in Iran

The release of greenhouse gases to the atmosphere is forecast by global climate models (GCM) to produce significant rainfall and temperature changes around the world. GCMs are not applicable in local studies. Studies downscaling global climate models to support local decision-makers in developing improved management plans in this region over the next century are therefore needed. Specifically, we focus on evaluating how climate change is likely to impact the range between min and max daily temperatures and the percent change in net rainfall depth over Ghara sou river basin. To account for differences and assess uncertainty stemming from model assumptions, 15 different GCMs with 3 different emission scenarios are employed to assess the changes and uncertainties of rainfall and temperature for three periods: 2011-2030, 2046-2065, and 2085-2099. Using a stochastical weather generator like LARS-WG, which has been employed in this study, is still common mostly between studies on climate change impacts on hydrological behaviors. LARS-WG uses the statistics of the historical data and generates weather variables with the same statistics. The results are satisfactory and reliable. Results for monthly rainfall show that in Jan and Feb usually face a general reduction in total rainfall, whereas from Oct to Dec there is an increase in net rainfall. Jun with the single highest increase compared to historical average experienced 185% rainfall increase compared to baseline for MIHR A1B and INCM3 B1 emission scenario. Sep for the middle and far-future scenarios, resulting in a 546% and 821% increase, respectively. Summers are the most affected by increases in the interquartile range for all three future periods; rainfall changes range from -27% to127% for the near future scenarios, -30% to 183% for the middle future scenarios, and -33% to 339% for the far future scenarios. Average seasonal min temperature increases with the highest absolute values of 3.54° in fall for the near future, 2.87° in summer for the middle future, and 11.81° in winter for the far future period. Based on the forecasted model results in three future horizons, Ghara sou river basin will experience higher temp in all seasons, and rainfall varies between -2% and 15%, compared to baseline historical rainfall records in the study area.