15 Sep 2022
15 Sep 2022
Status: this preprint is open for discussion.

Hydrological modelling on atmospheric grids; using graphs of sub-grid elements to transport energy and water

Jan Polcher1, Anthony Schrapffer2,1, Eliott Dupont3, Lucia Rinchiuso4,5, Xudong Zhou6, Olivier Boucher3, Emmanuel Mouche4, Catherine Ottlé4, and Jérôme Servonnat4 Jan Polcher et al.
  • 1LMD-IPSL, CNRS, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau Cedex, France
  • 2Centro de Investigaciones del Mar y la Atmósfera (CIMA), CONICET-UBA, CNRS, Intendente Güiraldes 2160 - Ciudad Universitaria - Pabellón II - 2do. piso (C1428EGA) C. A. Buenos Aires, Argentina
  • 3Institut Pierre-Simon Laplace (IPSL), CNRS, U. Sorbonne, Paris, France
  • 4LSCE-IPSL, CEA, CNRS, U. Paris-Saclay, Gif-sur-Yvette, France
  • 5METIS-IPSL, CNRS, U. Sorbonne, Paris, France
  • 6Institute of Industrial Science, University of Tokyo, Tokyo, Japan

Abstract. Land Surface Models (LSMs) use the atmospheric grid as their basic spatial decomposition because their main objective is to provide the lower boundary conditions to the atmosphere. Lateral water flows at the surface on the other hand require a much higher spatial discretization as they are closely linked to topographic details. We propose here a methodology to automatically tile the atmospheric grid into hydrological coherent units which are connected through a graph. As water is transported on sub-grids of the LSM, land variables can easily be transferred to the routing network and advected if needed. This is demonstrated here for temperature. The quality of the river networks generated, as represented by the connected hydrological transfer units, are compared to the original data in order to quantify the degradation introduced by the discretization method. The conditions the sub-grid elements impose on the time step of the water transport scheme are evaluated and a methodology is proposed to find an optimal value. Finally the scheme is applied in an off-line version of the ORCHIDEE LSM over Europe to show that realistic river discharge and temperatures are predicted over the major catchments of the region. The simulated solutions are largely independent of the atmospheric grid used thanks to the proposed sub-grid approach.

Jan Polcher et al.

Status: open (until 10 Nov 2022)

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Jan Polcher et al.

Jan Polcher et al.


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Short summary
The proposed graphs of hydrological sub-grid elements for an atmospheric models allows to integrate the topographical elements needed in land surface models for a realistic representation of horizontal water and energy transport. The study demonstrates the numerical properties of the automatically built graphs and the simulated water flows.