Numerical simulation and evaluation of soil temperature on the Qinghai–Xizang Plateau by the CLM4.5 model

The CRUNCEP V7 dataset was used to drive the Community Land Model version 4.5 (CLM4.5) to simulate the spatiotemporal changes in soil temperature in the Qinghai–Xizang Plateau from 1981 to 2016. The simulation results were compared with observations, ERA-Interim, and Global Land Data Assimilation System-Community Land Model (GLDAS-CLM) soil temperature reanalysis data. The results show that (1) the CLM4.5 can accurately reproduce the dynamic changes in the observed soil temperature over time in two soil layers (0–10 cm and 10–50 cm) at most sites, with a significant positive correlation with the observations. (2) The CLM4.5 can depict the spatial distribution of soil temperature in the plateau area, and the distribution characteristics are consistent with those of the reanalysis data. The soil temperature increases from north to south, and the values in the Qaidam Basin are significantly higher than those in the surrounding area. The CLM4.5 results are similar in value to the ERA-Interim product, while the GLDAS-CLM soil temperature values are generally higher. (3) The simulated value shows the trend of ‘increasing–decreasing-increasing–decreasing’ (+ − + −) from the west to the east in summer and autumn, while in winter and spring, the trend is generally increasing, but a decreasing trend is observed in some isolated locations. The temperature variation trends in the ERA-Interim data in winter and the GLDAS-CLM data in the middle of Sanjiangyuan in spring and the Qinghai Plateau in winter are consistent with those of the simulated data. The above results are all tested with 95% confidence. (4) From 1981 to 2016, the soil temperature on the plateau showed a significant upward trend, especially in spring and autumn. The two layers of the plateau have obvious seasonal changes, with the whole year characterised by a ‘single peak shape’. From March to September, the shallow soil temperature is higher than the deep soil temperature, and from October to February, the deep soil temperature is higher than the shallow soil temperature.