Trends in the frozen ground temperature on the Tibetan Plateau simulated by RegCM4.7-CLM4.5

The changing characteristics of the frozen ground are essential indicators of climate change. The soil temperature on the Tibetan Plateau (TP) during 1987–2018 is simulated using the coupled model of RegCM4.7-CLM4.5. The results show that there is a significant warming trend in the soil temperature on the TP, and the warming trend is higher in October–May (0.040 °C∙decade−1) than in June–September (0.026 °C∙decade−1), with the maximum value in February (0.058 °C∙decade−1). Spatially, the warming is most significant in the Three River Source Region (0.15~0.20 °C∙decade−1) and near the Himalayas and Kunlun Mountains (0.20~25 °C∙decade−1), with the warming trend greater in winter and spring than in summer and autumn. Air temperature, total precipitation, maximum snow depth, and maximum frozen ground depth are all significantly correlated to soil temperature. Air temperature (R = 0.851) and total precipitation (R = 0.411) are positively correlated with soil temperature, while maximum snow depth (R = −0.381) and maximum frozen ground depth (R = −0.770) are negatively correlated with it. Air temperature has a strong influence on the soil temperature in all the four seasons, while the effect of the total precipitation is strongest in autumn (R = 0.836). The retarding effects of maximum snow depth and maximum frozen ground depth are strongest in summer (R = −0.772 and −0.35, respectively). The frozen ground on the TP shows a degradation trend, and the consequent hydrological, ecological, and climatic effects deserve sufficient attention.