High‐Resolution Soil Moisture Data Reveal Complex Multi‐Scale Spatial Variability Across the United States

• Published in: Geophysical research letters 2022-08, Vol.49 (15), p.n/a
• Main Authors: Vergopolan, Noemi, Sheffield, Justin, Chaney, Nathaniel W., Pan, Ming, Beck, Hylke E., Ferguson, Craig R., Torres‐Rojas, Laura, Eigenbrod, Felix, Crow, Wade, Wood, Eric F.
• Format: Article
• Language: English
• Subjects: Agricultural ecosystems; Agriculture; Aquatic ecosystems; Atmospheric models; Biogeochemistry; Complexity; Datasets; Drought; Ecosystem dynamics; Freshwater; Freshwater ecosystems; heterogeneity; Hydroclimate; Hydrology; hyper‐resolution; Inland water environment; Landscape; Landslides; Moisture effects; Resolution; Satellites; Scale models; Scaling; Soil moisture; Soil properties; Spatial data; Spatial variability; Spatial variations; Variability; Vegetation; Water resources; Wildfires
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2022GL098586

Soil moisture (SM) spatiotemporal variability critically influences water resources, agriculture, and climate. However, besides site‐specific studies, little is known about how SM varies locally (1–100‐m scale). Consequently, quantifying the SM variability and its impact on the Earth system remains a long‐standing challenge in hydrology. We reveal the striking variability of local‐scale SM across the United States using SMAP‐HydroBlocks — a novel satellite‐based surface SM data set at 30‐m resolution. Results show how the complex interplay of SM with landscape characteristics and hydroclimate is primarily driven by local variations in soil properties. This local‐scale complexity yields a remarkable and unique multi‐scale behavior at each location. However, very little of this complexity persists across spatial scales. Experiments reveal that on average 48% and up to 80% of the SM spatial information is lost at the 1‐km resolution, with complete loss expected at the scale of current state‐of‐the‐art SM monitoring and modeling systems (1–25 km resolution). Plain Language Summary Soil moisture (SM) widely varies in space and time. This variability critically influences freshwater availability, agriculture, ecosystem dynamics, climate and land‐atmosphere interactions, and it can also trigger hazards such as droughts, floods, landslides, and aggravate wildfires. Limited SM observational data constrained our understanding of this variability and its impact on the Earth system. Here, we present the first continental assessment of how SM varies at the local scales using SMAP‐HydroBlocks – the first 30‐m surface SM data set over the United States. This study maps the SM spatial variability, characterizes the landscape drivers, and quantifies how this variability persists across larger spatial scales. Results revealed striking SM spatial variability across the United States, mainly driven by local spatial variations in soil properties and less so by vegetation and topography. However, this SM variability does not persist at coarser spatial scales resulting in extensive information loss. This information loss implicates inaccuracies when predicting non‐linear SM‐dependent hydrological, ecological, and biogeochemical processes using coarse‐scale models and satellite estimates. By mapping the SM spatial variability locally and its scaling behavior, we provide a pathway toward understanding SM‐dependent hydrological, biogeochemical, and ecological processes at local (an