Detecting significant decreasing trends of land surface soil moisture in eastern China during the past three decades (1979–2010)

Abstract

Understanding the historical trends and driving mechanism of China's soil moisture change is an important step in combating climate change. Using the time series satellite-derived Essential Climate Variable Soil Moisture (ECV_SM) product, we detected a significant decrease trend in land surface soil moisture in eastern China over a 32 year period . Theoretical sensitivity analysis suggested that soil moisture is regulated collectively by precipitation (P), potential evapotranspiration (PET), land surface conditions such as land cover/use changes, landscape features, irrigation and urban expansion, (m), and the water balance between input and output water supplies O (the input water supplies minus the output). The change in spatial pattern and temporal trend of P/PET is highly consistent with the corresponding change in soil moisture. The magnitude of soil moisture variation is also well correlated with that of P/PET (R 2 = 0.43; p < 0.001). Therefore, P/PET is believed to be the dominant factor in determining the temporal trends of soil moisture change. Among the 29 drainage basins with significant decreasing trend of soil moisture change, the areas of forest cover increased by 36.08% and the average topographic slope was twice steeper than that of other regions. Therefore, besides the climate factor (P/PET variable), land surface conditions (such as land cover changes and topographic) also played important roles in regulating the trend of regional soil moisture change. 1998;Uitdewilligen et al., 2003;Chen et al., 2012]. Due to its longer wavelength, the microwave can penetrate deeper into the media (i.e., soil and vegetation canopy) than the optical electromagnetic wave, and the CHEN ET AL.CHINA'S 32 YEAR SOIL MOISTURE 5177

Detecting Sustainability of Desertification Reversion: Vegetation Trend Analysis in Part of the Agro-Pastoral Transitional Zone in Inner Mongolia, China

“…The two-stage comparison showed an effect of interdecadal climatic fluctuation, which mitigated water limitation by increasing rainfall in the period (b) of 2000-2015, though it began at an extremely low level around 2000 [53]. As shown in previous research, over the last half-century, the annual mean temperature, precipitation, and relative humidity suggested a warming and drying trend in the Horqin Sandy Land [54]; over 1979-2010, the soil moisture of land surface was significantly decrease in the Liaohe Basin [55]; after 1997, a national "warming hiatus" and increase in "flash droughts" were observed in Northeastern China [56]. Thus, the trend of climate still involved uncertainties and gaps among increased rainfall, droughts, and vegetation enhancement in the HQA.…”

Consistency and Discrepancy of Global Surface Soil Moisture Changes From Multiple Model‐Based Data Sets Against Satellite Observations

“…Regional studies, such as those in China, India, and North America, indicated that ECV outperforms other soil moisture data sets (An et al, ; Chakravorty et al, ; Jia et al, ; Nicolai‐Shaw et al, ; Qiu et al, ; Zeng et al, ). In recent studies, ECV soil moisture has been widely accepted and used as reliable soil moisture observations for estimating long‐term changes of hydrological cycle in different regions (e.g., Chen et al, ; Feng, ; Feng & Zhang, ; Zohaib et al, ). Therefore, given the lack of a global‐scale high‐density network of in situ soil moisture measurements, as well as the large inconsistency of specifications of the existing in situ measurements (e.g., measurement methods, installation modes, and depths), this study employs ECV soil moisture as a reference to evaluate model‐based soil moisture data sets generated by different types of models (Dorigo et al, ).…”

“…Estimation of long‐term trends in soil moisture is one of the important scientific questions in climate change studies (e.g., Chen et al, ; Cheng et al, , ). Therefore, the long‐term trends estimated from different soil moisture data sets are compared.…”

“…Microwave observations are less affected by the atmosphere compared to other remote sensing techniques, but microwave signals from soil can still be attenuated by the atmosphere whose optical depth is primarily influenced by oxygen, water vapor, and cloud masking. The recently released multidecadal Essential Climate Variable (ECV) based on the assimilation of these satellite products provides comprehensive satellite observations of surface soil moisture since 1979 and has been broadly used (Chen et al, ; Feng, ; Liu et al, , ).…”

Attribution of Global Soil Moisture Drying to Human Activities: A Quantitative Viewpoint

“…Based on satellite observations and model simulations, widespread soil moisture (SM) drying in the root zone layer (i.e., at depths of 0–100 cm) has been witnessed globally in past decades (e.g., Cheng et al, ; Cheng & Huang, ; Chen et al, ; Dai, ). Global‐scale SM drying has also been corroborated by meteorological drought indices, such as the Palmer Drought Severity Index (Dai et al, ), Standardized Precipitation Index (Hirschi et al, ; Wang et al, ; Zhang et al, ), and Aridity Index (Huang et al, ).…”