Abstract
The change of soil temperature can affect the regional climate, so it is of great significance to research the spatial and temporal evolution characteristics of regional soil temperature over a long period of time for the research of the land-air interaction, climate change and ecological agricultural construction. We use the v2.0 and v2.1 data set combined with GLDAS and Noah models to analyze the spatiotemporal variation of temperature in soil layers of 0 - 200 cm in China during the period of 71 years from 1948 to 2018. Firstly, the Mann-Kendall test method is used to research the variation trend of soil temperature over the past 71 years in China and the spatial variation of these trends. Secondly, by calculating the spatiotemporal coefficient of variation (CV) of soil temperature, the spatial-temporal fluctuation of soil temperature in China is further studied and analyzed. Finally, the Hurst index is used to analyze the possible future trend of soil temperature in China. Based on these methods, we have drawn the following conclusions: 1) The soil temperature in most areas of northern China had an increasing trend, especially in the northeast China. The soil temperature in most of the south China had a decreasing trend. The temperature trends of the four soil layers had little difference, and it remained stable on the whole. 2) The regional difference of soil temperature in China remained stable before 1999, and decreased suddenly in 2000. After 2008, the regional difference increased. Compared with the previous period, the temperature in some areas increased or decreased abnormally. 3) The soil temperature in eastern, southeast China and Xinjiang had a relatively significant variation in the 71 years. From 0 - 10 cm soil surface to 100 - 200 cm soil bottom, the spatial difference of temperature gradually decreased, which was due to the fact that the soil temperature was more affected by the surface atmospheric temperature. 4) The soil temperature in the north and northwest of China will continue to grow, and in the southern—most will continue to decrease. The soil temperature in the north of central China will become a decreasing trend, while the temperature in the south of central China will become an increasing trend.
Highlights
Soil temperature, an important physical property of soil, can affect the energy and water exchange between land and atmosphere by changing the surface thermal state, and affect the regional climate [1]
We use the v2.0 and v2.1 data set combined with global land data assimilation system (GLDAS) and Noah models to analyze the spatiotemporal variation of temperature in soil layers of 0 - 200 cm in China during the period of 71 years from 1948 to 2018
Jiang et al [14] and Wang Wen et al [15] confirmed the applicability of GLDAS in China, and the data had been widely used in the research of soil temperature in China [5] [9] [16] [17] [18]
Summary
An important physical property of soil, can affect the energy and water exchange between land and atmosphere by changing the surface thermal state, and affect the regional climate [1]. According to the ground climatic data from 1971 to 2000 of annual and monthly average soil temperature, air temperature and precipitation, Zhang Huizhi et al [11] analyzed the seasonal variation of soil temperature in China as well as the characteristics of the regional differentiation, and analyzed the influence of temperature and precipitation on soil temperature. Based on IBIS model, Zhu Qiu’an [12] simulated the annual and monthly average soil temperature of the upper soil layer of 1 m in China from 1955 to 2006, and they used the Mann-Kendall method to analyze the trend of annual and monthly average soil temperature They drew the conclusion that for the annual average soil temperature, the north had significant increasing trend, but the south had weak increasing trend. The fourth part carries on the summary analysis to draw the research conclusion
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