Climate change has become one of the most widely discussed topics in the world due to its significant impact on human lives. Climate change impact prediction is the key feature when it comes to select suitable adaptation strategies for future climate change scenarios. The weather and climate prediction can be done by many weather models available. This study aims to compare the performance of WRF and RegCM weather models on Upper Mahaweli river basin, so the WRF (Weather Research & Forecasting Model) & RegCM (Regional Climate Model) Models were calibrated and validated to the upper Mahaweli basin using Observed point rainfall data of four gauging stations within the study area and Global Climate Model (GCM) data. During the calibration process the Physics options of both models were changed to fine-tune the models to our study area. The sensitivity of the change of physics options were assessed by calculating the Root Mean Square Error (RMSE) values. Three Extreme events with known precipitations were selected from the precipitation data obtained. They were used for calibration, validation and comparison respectively.
