Preprints
https://doi.org/10.5194/egusphere-2024-2412
https://doi.org/10.5194/egusphere-2024-2412
22 Aug 2024
 | 22 Aug 2024
Status: this preprint is open for discussion.

Implementing deep soil and dynamic root uptake in Noah-MP (v4.5): Impact on Amazon dry-season transpiration

Carolina A. Bieri, Francina Dominguez, Gonzalo Miguez-Macho, and Ying Fan

Abstract. Plant roots act as critical pathways of moisture from the subsurface to the atmosphere. Deep moisture uptake by plant roots can provide a seasonal buffer mechanism in regions with a well-defined dry season such as the southern Amazon. Most existing state-of-the-art earth system models cannot fully capture the required subsurface-to-atmosphere processes, including groundwater dynamics, a sufficiently deep soil column, dynamic root water uptake, and a fine model spatial resolution (<5 km).

To address this, we present DynaRoot, a dynamic root water uptake (RWU) scheme implemented within the Noah-MultiParameterization (Noah-MP) land surface model, a widely used model for studying kilometer-scale regional land surface processes. Our modifications include the implementation of DynaRoot, eight additional resolved soil layers reaching a depth of 20 m, and soil properties that vary with depth. DynaRoot is computationally efficient and ideal for regional- or continental-scale climate simulations. We perform four 20 year uncoupled Noah-MP experiments for a region in the southern Amazon basin. Each experiment incrementally adds physical processes. The experiments include default Noah-MP with free drainage (FD); addition of a groundwater scheme that resolves water table variations (GW); addition of eight soil layers and soil properties that vary with depth (SOIL), and addition of DynaRoot (ROOT).

Our results show that DynaRoot allows mature forests in upland regions to avoid water stress during dry periods by taking up moisture from the deep vadose zone (where antecedent precipitation is still draining downward). Conversely, RWU in valleys can take up moisture from groundwater (while remaining constrained by the water table). Temporally, we capture a seasonal shift in RWU from shallower layers in the wet season to deeper soil layers in the dry season, particularly over regions with dominant evergreen broadleaf (forest) vegetation. Compared to the control case, there is a domain-average increase in transpiration of about 29 % during dry months in the ROOT experiment. Critically, the ROOT experiment performs best in simulating the temporal evolution of dry-season transpiration and evapotranspiration (ET) compared with an observational ET product. Future work will explore the effect of the DynaRoot uptake scheme on atmospheric variables in a coupled modeling framework.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Carolina A. Bieri, Francina Dominguez, Gonzalo Miguez-Macho, and Ying Fan

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2412', Anonymous Referee #1, 11 Oct 2024 reply
Carolina A. Bieri, Francina Dominguez, Gonzalo Miguez-Macho, and Ying Fan

Data sets

Model configuration files and forcing data for Bieri et al. (2024) EGU GMD Carolina A. Bieri, Francina Dominguez, Gonzalo Miguez-Macho, and Ying Fan https://doi.org/10.5281/zenodo.13061970

Model code and software

HRLDAS/Noah-MP model code for Bieri et al. (2024) EGU GMD Carolina A. Bieri, Francina Dominguez, Gonzalo Miguez-Macho, and Ying Fan https://doi.org/10.5281/zenodo.13137185

Python processing and analysis scripts for Bieri et al. (2024) EGU GMD Carolina A. Bieri, Francina Dominguez, Gonzalo Miguez-Macho, and Ying Fan https://doi.org/10.5281/zenodo.13137808

Carolina A. Bieri, Francina Dominguez, Gonzalo Miguez-Macho, and Ying Fan

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Short summary
Access to deep moisture below the earth's surface is important for vegetation in areas of the Amazon where there is little precipitation for part of the year. Most existing numerical models of the earth system cannot capture where and when deep root water uptake occurs. In this study, we address this by adding a new root water uptake feature to an existing model. Adding this feature increases dry month transpiration and improves the model's simulation of the annual transpiration cycle.