Validation of temperature and precipitation variables of CMIP5 models in Iran under CORDEX-WAS and NEX-GDDP projects

No study has so far evaluated the NEX-GDDP and CORDEX-WAS downscaling methods to validate the output of CMIP5 models in Iran for temperature and precipitation parameters. Therefore, this study is the first in Iran to compare the MPI-ESM-LR model performance from the CMIP5 model series for temperature and precipitation variables with the combined approach of dynamic and statistical downscaling methods for the historical period of 1980-2005. The verification was performed using the MBE, RMSE, and R statistics. The slope of the data trend in the time series is estimated using Sen’s non-parametric method. The findings revealed that degrees of bias equal to -0.34 and -0.46 C were recorded in CORDEX and NEX-GDDP projects, respectively, indicating the better performance of the MPI-ESM-LR model under the CORDEX dynamic downscaling project than the NEX-GDDP statistical project in temperature simulation. In both projects, the maximum and minimum temperatures were simulated in Iran's southern coasts and north-western heights. The MBE index shows a decreased bias in the NEX-GDDP project (-2.60 mm) compared to the CORDEX project (-8.21 mm), suggesting the better performance of the MPI-ESM-LR model in the NEX-GDDP project than the CORDEX project in precipitation simulation. Both projects' maximum and minimum precipitations were simulated in the Zagros highlands and the southeast of Iran, respectively.