Convection-permitting climate simulations with COSMO-CLM over northwestern Turkiye under the RCP8.5 scenario

The performance of the climate simulations by the regional climate model COSMO-CLM forced by MPI-ESM-LR, as well as projected future temperature and precipitation conditions over northwestern Turkiye at the convection-permitting resolution, are shown in this study. In terms of mean, maximum and minimum temperatures and daily total precipitation, the model response was examined. Comparisons with observations were made on an annual and seasonal basis. The convection-permitting model (0.0275 degrees) provides a satisfactory representation of annual and seasonal mean temperatures according to bias, MAE and RMSE. Better results were found for precipitation with respect to RE, MAE and RMSE. Finally, we used the RCP8.5 emission scenario to investigate future climate changes in terms of average temperature and precipitation variations for northwestern Turkiye, including Istanbul, over two projection periods (2041-2060 and 2071-2090) compared to the reference period (1991-2005). The model predicts significant warming in northwestern Turkiye, particularly in Istanbul and its environs, by the end of the century, as well as a general decrease in precipitation, especially evident in the spring and summer. The findings of this study can be used to develop climate adaptation policies based on temperature and precipitation variables in and around the study area.