One-kilometre monthly air temperature and precipitation product over the Mongolian Plateau for 1950-2020

The fragile ecological environment of the Mongolian Plateau (MP) is sensitive to climate change. It is necessary to fully understand the temperature and precipitation changes on the MP to ensure regional sustainable development. Most existing studies are conducted based on station observations which suffer from sparse distribution and limited spatial representativeness and cannot perfectly represent the climatic conditions of the whole region. By contrast, the long-term, spatially continuous reanalysis products offer new opportunities for MP climate change research. However, the coarse spatial resolution and large uncertainties of reanalysis data limit their applicability to provide reliable climate information at finer scales. Within the delta downscaling framework, we downscale and correct the state-of-the-art European Centre for Medium-range Weather Forecasts ReAnalysis 5 land portion (ERA5-Land) using a high-resolution WorldClim reference climatology and generate a long-term (1950-2020) 1-km monthly air temperature and precipitation downscaled dataset. During the downscaling process, the results obtained by nearest neighbour, bilinear and bicubic interpolation methods are evaluated and compared. Air temperature result of bilinear method and precipitation result of nearest neighbour method, which have the best accuracy, are taken as the final downscaled data. The evaluation shows that the downscaled data has acceptable accuracy (overall MBE = -0.41 degrees C, Corr = 0.997, RMSE = 1.51 degrees C for air temperature, and MBE = 1.58 mm.month(-1), Corr = 0.747, RMSE = 24.24 mm.month(-1) for precipitation), and outperforms the original ERA5-Land and widely used Climatic Research Unit (CRU) data. In addition, the downscaled data can also provide accurate and detailed temperature and precipitation change trends over the MP. With fine spatial resolution, long-time span and good spatial continuity, the downscaled air temperature and precipitation will be a useful data source to explore climate change over the MP.