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Global Surface Soil Moisture Drydown Patterns
  • Binayak P. Mohanty,
  • Vinit Sehgal,
  • Nandita Gaur
Binayak P. Mohanty
Texas A&M University

Corresponding Author:[email protected]

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Vinit Sehgal
Texas A&M University
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Nandita Gaur
University of Georgia
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Understanding the global soil moisture (SM) dynamics and its governing controls beyond Darcy Scale is critical for various hydrologic, meteorological, agricultural, and environmental applications. In this study, we parameterize the pathways of the seasonal drydowns using global surface soil moisture (θ_RS) observation from SMAP satellite (between 2015 and 2019) at 36km X 36km. We develop a new data-driven non-parametric approach to identify the canonical shapes of θ_RS drydown, followed by a non-linear least-squares parameterization of the seasonal drydown pathways at each SMAP footprint. The derived parameters provide the effective soil water retention parameters (SWRPeff), land-atmospheric coupling strength, soil hydrologic regimes for SMAP footprint. Depending on footprint heterogeneity, climate and season, the characteristics curves comprising different drydown phases are discovered at SMAP footprints. Drydown curves respond to the within-footprint changes in the meteorological drivers, land-surface characteristics and the soil-vegetative and atmospheric dynamics. Drydown parameters display high inter-seasonal variability, especially in grasslands, croplands and savannah landscapes due to significant changes in the landscape characteristics and moisture patterns at the subgrid-scale. Soil texture exert influence on the characteristics soil water retention and drydown parameters only when the footprint mean θ_RS is low, specifically in arid and sparsely vegetated regions. The influence of soil texture on the inter-seasonal variability of SWRPeff is low compared to landuse and climate at RS-footprint scale. The global understanding of characteristics SM drydown features at SMAP footprints provides a significant step towards a scale-specific, effective soil hydrologic parameterization for various applications.
Jan 2021Published in Water Resources Research volume 57 issue 1. 10.1029/2020WR027588