Abstract
Abstract. Due to their shallow vertical support, remotely sensed surface soil moisture retrievals are commonly regarded as being of limited value for water budget applications requiring the characterization of temporal variations in total terrestrial water storage (dS ∕ dt). However, advances in our ability to estimate evapotranspiration remotely now allow for the direct evaluation of approaches for quantifying dS ∕ dt via water budget closure considerations. By applying an annual water budget analysis within a series of medium-scale (2000–10 000 km2) basins within the United States, we demonstrate that, despite their clear theoretical limitations, surface soil moisture retrievals derived from passive microwave remote sensing contain statistically significant information concerning dS ∕ dt. This suggests the possibility of using (relatively) higher-resolution microwave remote sensing products to enhance the spatial resolution of dS ∕ dt estimates acquired from gravity remote sensing.
Highlights
Within the past decade, the analysis of data products from the Gravity Recovery and Climate Experiment (GRACE) satellite mission (Tarpley et al, 2004a, b) has led to an enhanced appreciation of the role played by interannual variations of total terrestrial water storage within the terrestrial water budget (Chen et al, 2009; Rodell et al, 2007; Syed et al, 2008)
Confirming recent work with GRACE, results demonstrate the importance of dS / dt for closing the annual water budget
GRACE-based dSGR / dt estimates appear to provide a reliable source of such information within large-scale river basins with relatively low annual snowfall totals and anthropogenic management (Figs. 2–3)
Summary
The analysis of data products from the Gravity Recovery and Climate Experiment (GRACE) satellite mission (Tarpley et al, 2004a, b) has led to an enhanced appreciation of the role played by interannual variations of total terrestrial water storage (dS / dt) within the terrestrial water budget (Chen et al, 2009; Rodell et al, 2007; Syed et al, 2008). Microwave-based surface soil moisture (θ ) retrievals provide a direct assessment of soil water storage that can be obtained at relatively finer resolutions (typically ∼ 1000 km2) Such retrievals are hampered by both shallow vertical support (reflecting soil moisture conditions only in the top several centimeters of the soil column) and substantially reduced accuracy for dense vegetative cover. Recent empirical work demonstrates that microwave-based θ retrievals are generally well-correlated with GRACE-based storage estimates (Abelen and Seitz, 2013; Abelen et al, 2015) This suggests that θ retrievals retain some value for water-balance studies – at spatial scales finer than the resolution of GRACE products
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