Temporal and Spatial Variation of Soil Moisture and Its Possible Impact on Regional Air Temperature in China

Guolin Han,Guofeng Sun,Yuying Pan,Yu Song,Shangqian Ma,Zizhong Wang,Zhihua Pan,Na Huang,Ziyuan Zhang,Ruiqi Peng,Jialin Wang,Cong Liu

doi:10.3390/w12061807

Abstract

Soil moisture is closely related to the hydrosphere, atmosphere, and biosphere, which makes it one of the most significant climate variables. Using data from the National Environmental Forecasting Center (NCEP), this paper analyzes the temporal and spatial characteristics of soil moisture at a depth of 0–10 cm in China for the period of 1948 to 2014. In addition, the soil moisture’s possible interaction with air temperature is explored. Mainly using statistical analysis, the results showed that annual soil moisture decreased significantly (p < 0.01) in most areas. The tendency of decreasing soil moisture was relatively higher in spring and autumn than that in summer and winter. As to the national annual average soil moisture, there was a sudden change in the 1970s. The soil moisture had a relatively high value with a larger deviation before the abrupt change, but after that, the soil moisture was at a relatively low level with a smaller deviation. It was also found that the soil moisture at 0–10 cm showed a negative correlation with the 2-m air temperature above ground in the northern part of China, where the speed of the temperature rise was higher. The results are expected to help improve the understanding of the link between regional soil moisture variation and climate change.

Highlights

Soil moisture is a key variable of the climate system [1], as well as an important variable in biogeochemical cycles, connecting the atmosphere, hydrosphere, and biosphere [2,3,4,5]
The relative low-value areas are concentrated in northwestern China (NWC), while the relative high-value areas are in central China (CC) and Northeastern China (NEC). (2) Soil moisture is prone to decrease in all four seasons significantly (p < 0.01); the rate of decrease is relatively larger in spring and autumn, and the amplitude is smaller in summer and winter
All the regions show a decreasing trend except for southern China (SC), with the most significant decreases occurring in CC in spring, northern China (NC) in summer, and NEC in autumn

Summary

Introduction

Soil moisture is a key variable of the climate system [1], as well as an important variable in biogeochemical cycles, connecting the atmosphere, hydrosphere, and biosphere [2,3,4,5]. Soil moisture can alter the transmission and distribution of water and energy on land surfaces by changing surface evapotranspiration, albedo, and soil thermal capacity. This causes a change in atmospheric circulation, eventually resulting in a climate anomaly [6]. Soil moisture, being the main variable in the earth and biosphere interface and its biochemical cycle, is essential in the study of many other relevant issues, such as food security, human health, and ecosystem function [10,11]

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