Climate change projection over the Tibetan Plateau based on a set of RCM simulations

Tibetan Plateau (TP, with the height > 3000 m) is a region with complex topographical features and a large diversity of climate both in space and time. The use of higher resolution regional climate models (RCMs) to downscale global climate model simulations is of high importance. In the present study, future climate change over TP and the surrounding areas is investigated based on the ensemble of a set of the 21st century climate change projections using the RCM RegCM4. The model is driven by five different GCMs at a grid spacing of 25 km under RCP4.5. The focus is on the December-January-February (DJF), June-July-August (JJA), and annual mean temperature and precipitation, with comparisons against the driving GCMs also provided. Overall, the RegCM4 greatly improves the simulation by providing finer scale spatial details of both temperature and precipitation distributions over the region. The topographic effects are well reproduced by RegCM4 but not the GCMs. For the projected future changes, general warming and increase in precipitation are found in both GCM and RegCM4 simulations. However, substantial differences exist in both the spatial distribution and magnitude of the changes. The added value of RegCM4 for temperature, in addition to the finer spatial details, is characterized by a more pronounced warming in DJF over TP compared to its surrounding areas. The projected changes of precipitation show also differences between RegCM4 and the driving GCMs. The increase of precipitation is more pronounced and over the basins in DJF for RegCM4, and in general with a better agreement across the simulations compared to the driving GCMs.