Submitted as: development and technical paper 28 Oct 2020

Submitted as: development and technical paper | 28 Oct 2020

Review status: this preprint is currently under review for the journal GMD.

Two-way coupling between the sub-grid land surface and river networks in Earth system models

Nathaniel W. Chaney1, Laura Torres-Rojas1, Noemi Vergopolan2, and Colby K. Fisher3 Nathaniel W. Chaney et al.
  • 1Department of Civil and Environmental Engineering, Duke University, Durham, NC, USA
  • 2Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, USA
  • 3Princeton Climate Analytics, Princeton University, Princeton, NJ, USA

Abstract. Over the past decade, there has been appreciable progress towards modeling the water, energy, and carbon cycles at field-scales (10–100 m) over continental to global extents. One such approach, named HydroBlocks, accomplishes this task while maintaining computational efficiency via sub-grid tiles, or Hydrologic Response Units (HRUs), learned via a hierarchical clustering approach from available global high-resolution environmental data. However, until now, there has yet to be a macroscale river routing approach that is able to leverage HydroBlocks' approach to sub-grid heterogeneity, thus limiting the added value of field-scale land surface modeling in Earth System Models (e.g., riparian zone dynamics, irrigation from surface water, and interactive floodplains). This paper introduces a novel dynamic river routing scheme in HydroBlocks that is intertwined with the modeled field-scale land surface heterogeneity. The primary features of the routing scheme include: 1) the fine-scale river network of each macroscale grid cell's is derived from very high resolution (< 100 m) DEMs; 2) the inlet/outlet reaches of each macroscale grid cell are linked to assemble the continental river networks; 3) the river dynamics are solved at a reach-level via the Kinematic wave assumption of the Saint-Venant equations; 4) a two-way coupling is established between each sub-grid tile and the river network. To implement and test the novel approach, a 1.0-degree bounding box surrounding the Atmospheric Radiation and Measurement (ARM) Southern Great Plains (SGP) site in Northern Oklahoma (United States) is used. The results show: 1) the implementation of the two-way coupling between the land surface and the river network leads to appreciable differences in the simulated spatial heterogeneity of the surface energy balance; 2) a limited number of tiles (~300 per 0.25-degree cell) are required to approximate the fully distributed simulation adequately; 3) the surface energy balance partitioning is sensitive to the river routing model parameters. The resulting routing scheme provides an effective and efficient path forward to enable a two-way coupling between the high-resolution river networks and existing tiling schemes within Earth system models.

Nathaniel W. Chaney et al.

Status: final response (author comments only)
Status: final response (author comments only)
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Nathaniel W. Chaney et al.

Nathaniel W. Chaney et al.


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Short summary
Although there have been significant advances in river routing and sub-grid heterogeneity (i.e., tiling) schemes in Earth system models over the past decade, there has yet to be a concerted effort to couple these two concepts. This paper aims to bridge this gap through the development of a two-way coupling between sub-grid tiles and river networks in a field-scale resolving land surface model. The scheme is implemented and tested over a 1 arc degree domain in Oklahoma, United States.