Document Type

Article

Publication Date

10-16-2024

Abstract

A lack of high-density rootzone soil moisture (θRZ) observations limits the estimation of continental-scale, space-time contiguous θRZ dynamics. We derive a proxy of daily θRZ dynamics — active rootzone degree of saturation (SRZ) — by recursive low-pass (LP) filtering of surface soil moisture (θS) within a terrestrial water-energy coupling (WEC) framework. We estimate the LP filter parameters and WEC thresholds for the piecewise-linear coupling between SRZ and evaporative fraction (EF) at remote sensing and field scale over the Contiguous U.S. We use θS from the Soil Moisture Active-Passive (SMAP) satellite and 218 in-situ stations, with EF from the Moderate Resolution Imaging Spectroradiometer. The estimated SRZ compares well against SMAP Level-4 estimates and in-situ θRZ, at the corresponding scale. The instantaneous hydrologic state (SRZ) vis-à-vis the WEC thresholds is proposed as a rootzone soil moisture stress index (SMSRZ) for near-real-time operational agricultural drought monitoring and agrees well with established drought metrics.

Publication Source (Journal or Book title)

Geophysical Research Letters

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