Evaluation of RegCM4 Regional Climate Model simulations for the land surface water budget components in Toyserkan plain

In regional and local climate studies usually coarse- resolution global climate models’ outputs are downscaled to produce necessary fine scale data. Regional climate modeling is a dynamical downscaling method. In this study HadGEM2 general circulation model outputs have been downscaled by RegCM4 Regional Climate Model coupled with CLM4.5 land surface model. The model was run over Toyserkan plain for a reference period (1999-2005) and up coming period (2015-2025). For reference period, daily, monthly and yearly modeled precipitation, temperature and runoff were compared with observed values at monitoring stations in the region. Modeling efficiency, correlation coefficient, bias, mean absolute error and root mean squared error statistical indices were used to evaluate model’s simulations. Model shows its best performance for monthly temperature, runoff and precipitation respectively. Predictions are based on RCP4.5 scenario of the Fifth Assessment Report of Intergovernmental panel on climate change. For this period spatiotemporal variations of surface water budget components including precipitation, evapotranspiration and runoff have been studied and water balance equation in the catchment has been evaluated.  Finally considering small area of the catchment and short time of prediction period that does not allow to detect impacts of climate change, model performance in estimating water balance for the catchment is acceptable.