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Global Terrestrial Water-Energy Coupling Across Scales
  • Deanroy Mbabazi,
  • Vinit Sehgal,
  • Binayak mohanty
Deanroy Mbabazi
Texas A&M University Department of Biological and Agricultural Engineering
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Vinit Sehgal
Texas A&M University Department of Biological and Agricultural Engineering
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Binayak mohanty
Texas A&M University Department of Biological and Agricultural Engineering

Corresponding Author:[email protected]

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Abstract

Terrestrial water energy coupling (WEC), in the form of the non-linear relationship between Soil Moisture (SM) and evaporative fraction (EF, ratio of actual and potential evapotranspiration), controls critical ecohydrological processes. We investigate and parameterize the evolution of global SM–EF coupling from the field to remote-sensing (RS)-footprint. The field-scale EF and SM were obtained from 163 eddy covariance (EC) and SM sensors at various network (Texas Water Observatory and FLUXNET) sites around the globe. Remote-sensing (RS)-scale EF and SM estimates were obtained from Moderate-resolution Imaging Spectroradiometer (MODIS) and Soil Moisture Active Passive (SMAP) sensors, respectively. We estimate the effective thresholds of the WEC regimes from both EC and satellite datasets to highlight the influence of subgrid-scale heterogeneity, scaling, and observational constraints on the evolution of WEC regimes from field to RS-footprint scale. We compare the critical WEC thresholds of the water- and energy-limited regimes with an SM drydown-based approach and highlight the similarities between both methods in partitioning dominant WEC regimes. EF and SM are strongly coupled in dryland arid and semi-arid regions compared to humid climates. WEC regimes and thresholds have strong interseason variability due to dynamic interactions between soil, vegetation, and atmosphere at the RS-footprint scale. In contrast, field-scale SM-EF coupling is influenced predominantly by agricultural /land-use practices and soil conditions. Hence, future development of Earth-System/Land-Surface models must account for the inter-scale differences in the coupling between terrestrial water and energy fluxes representative of the “ effective” processes at large spatial scales.
11 Apr 2024Submitted to Ecohydrology
11 Apr 2024Assigned to Editor
11 Apr 2024Submission Checks Completed
23 Apr 2024Reviewer(s) Assigned