Analysis on the Temporal and Spatial Characteristics of the Shallow Soil Temperature of the Qinghai-Tibet Plateau

Abstract Shallow soil refers to the soil layer within 50 cm underground. Shallow soil temperature (ST) directly or indirectly affects many processes in the soil, such as seed germination, plant growth, water evaporation. Shallow ST is also affected by solar radiation, atmospheric circulation, air temperature and precipitation changes. Therefore, the study of shallow ST is of great significance in understanding surface energy, water cycle, ecology and climate change. This work collected the observational data from 141 meteorological stations on the Qinghai-Tibet Plateau from 1981 to 2020, analyzed the ST as well as its temporal and spatial change characteristics at different levels. The results show that: 1) The shallow ST has a gradually increasing trend from north to south, from west to east. From the perspective of time characteristics, the increasing trend is obvious. The temperature increase of 0-20cm (the surface layer of the shallow soil) is roughly the same. The average annual ST is 9.15–9.57 ℃, the interdecadal variabilities are 0.49–0.53 K/10a. The average annual ST of 40cm (the bottom layer) is 8.69 ℃, the interdecadal variability reaches by 0.98 K/10a; 2) Considering the 7 regions, the warming trend is obvious, and there are certain regional differences. The average annual ST in different regions ranges from 5.2°C (Northeast of the Plateau) to 17.1°C (Western Sichuan Plateau), with a difference of nearly 12K; the standard deviation ranges from 0.40K (Western Sichuan Plateau) to 0.61K (Qiangtang Plateau), with a difference of 0.21K. This work is significant for understanding the characteristics of the ST evolution and the land-atmosphere interaction on the Qinghai-Tibet Plateau.