Spatial clusters and temporal trends of seasonal surface soil moisture across China in responses to regional climate and land cover changes

Abstract

Investigating the spatiotemporal changes of regional surface soil moisture in responses to climate and land cover changes is vital for understanding the underlying mechanisms of hydrological processes. While previous studies mainly attributed the causes of soil moisture changes to climatic factors, few took land cover into consideration. We analyzed the seasonal-differentiated effects of climate and land cover changes on surface soil moisture of China's 80 drainage basins using the Essential Climate Variable Soil Moisture product spanning the 1979-2010 period. The low-low spatial clusters of annual (Jan-Dec), warm-season (Apr-Sept) and cool-season (Oct-Dec and Jan-Mar) surface soil moisture have spread from Northwest China to northeast and even Central China during the past three decades. In cool seasons, significant decreasing trends of surface soil moisture in most drainage basins of Northwest, Northeast, Central, and South China were detected. But in warm seasons, the surface soil moisture in Central and South China showed significant increasing trends. Precipitation, potential evapotranspiration and the ratio of the two are three driving forces for warm-season surface soil moisture changes in Northeast and Northwest China. These climatic factors are main contributors to the declining trends of cool-season surface soil moisture in Central and South China. Land cover changes showed to be the major factor driving the significant decreasing trends of cool-season surface soil moisture in Northwest, Central, and South China. Due to vegetation's self-shading effect, the large-scale reforestation and vegetation growth are believed as main causes of the increasing trends of warm-season surface soil moisture in Central and South China.

ESA CCI Soil Moisture for improved Earth system understanding: State-of-the art and future directions

“…Feng (2016) assessed the drivers of trends in ESA CCI SM COMBINED v02.2 and concluded that at the global scale climate change is by far the most important driver of long-term changes in soil moisture, although at the regional level land cover and land use change may play a significant role. Similar conclusions were drawn by regional studies over China (Chen et al, 2017;Liu et al, 2015;Meng et al, 2017). Other studies analysed the variability and trends in ESA CCI SM in relation to other atmospheric variables and circulation patterns over Asia (Shrivastava et al, 2016(Shrivastava et al, , 2017Zhan et al 2017).…”

Global Surface Soil Moisture Dynamics in 1979–2016 Observed from ESA CCI SM Dataset

“…Soil moisture dynamics are closely related to changes of precipitation [15,[39][40][41] which is the main source of SM. During the 1979-2016 period, annual precipitations have significantly changed in 15% of the valid global lands except in the Amazon and Congo River basins.…”

A Simplified Climate Change Model and Extreme Weather Model Based on a Machine Learning Method

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