Evaluation of CORDEX regional climate models in simulating temperature and precipitation over the Tibetan Plateau

Using a regional climate model (RCM) is generally regarded as a promising approach in researching the climate of the Tibetan Plateau, due to the advantages provided by the high resolutions of these models. Whilst previous studies have focused mostly on individual RCM simulations, here, multiple RCMs from the Coordinated Regional Climate Downscaling Experiment are evaluated in simulating surface air temperature and precipitation changes over the Tibetan Plateau using station and gridded observations. The results show the following: (1) All RCMs consistently show similar spatial patterns, but a mean cold (wet) bias in the temperature (precipitation) climatology compared to station observations. The RCMs fail to reproduce the observed spatial patterns of temperature and precipitation trends, and on average produce greater trends in temperature and smaller trends in precipitation than observed results. The multi-model ensemble overall produces superior trends in both simulated temperature and precipitation relative to individual models. Meanwhile, RegCM4 presents the most reasonable simulated trends among the five RCMs. (2) Considerable dissimilarities are shown in the simulated quantitative results from the different RCMs, which indicates a large model dependency in the simulation of climate over the Tibetan Plateau. This implies that caution may be needed when an individual RCM is used to estimate the amplitude of climate change over the Tibetan Plateau. (3) The temperature (precipitation) in 2016-35, relative to 1986-2005, is projected by the multi-model ensemble to increase by 1.38 +/- 0.09 degrees C (0.8% +/- 4.0%) and 1.77 +/- 0.28 degrees C (7.3% +/- 2.5%) under the RCP4.5 and RCP8.5 scenario, respectively. The results of this study advance our understanding of the applicability of RCMs in studies of climate change over the Tibetan Plateau from a multiple-RCM perspective.