13 Jul 2021

13 Jul 2021

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

Unravelling the contribution of potential evaporation formulation to uncertainty under climate change

Thibault Lemaitre-Basset1,2, Ludovic Oudin1, Guillaume Thirel2, and Lila Collet2,a Thibault Lemaitre-Basset et al.
  • 1Sorbonne Université, CNRS, EPHE, UMR 7619 METIS, Case 105, 4 place Jussieu, F-75005 Paris, France
  • 2Université Paris-Saclay, INRAE, HYCAR research unit, Hydrology Research Group, Antony, France
  • aNow at: EDF R&D, OSIRIS Department, 7 boulevard Gaspard Monge, 91120 Palaiseau, France

Abstract. The increasing air temperature in a changing climate will impact actual evaporation and have consequences for water resources management in energy-limited regions. In many hydrological models, evaporation is assessed by a preliminary computation of potential evaporation (PE) representing the evaporative demand of the atmosphere. Therefore, in impact studies the quantification of uncertainties related to PE estimation, which can arise from different sources, is crucial. Indeed, a myriad of PE formulations exist and the uncertainties related to climate variables cascade into PE computation. So far, no consensus has emerged on the main source of uncertainty in the PE modelling chain for hydrological studies. In this study, we address this issue by setting up a multi-model and multi-scenario approach. We used seven different PE formulations and a set of 30 climate projections to calculate changes in PE. To estimate the uncertainties related to each step of the PE calculation process (namely Representative Concentration Pathways, General Circulation Models, Regional Climate Models and PE formulations), an analysis of variance decomposition (ANOVA) was used. Results show that PE would increase across France by the end of the century, from +40 to +130 mm/year. In ascending order, uncertainty contributions by the end of the century are explained by: PE formulations (below 10 %), then RCPs (above 20 %), RCMs (30–40 %) and GCMs (30–40 %). Finally, all PE formulations show similar future trends since climatic variables are co-dependent to temperature. While no PE formulation stands out from the others, in hydrological impact studies the Penman-Monteith formulation may be preferred as it is representative of the PE formulations ensemble mean and allows accounting for climate and environmental drivers co-evolution.

Thibault Lemaitre-Basset et al.

Status: open (until 07 Sep 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Thibault Lemaitre-Basset et al.

Model code and software

R functions to compute potential evaporation Lemaitre-Basset, Thibault, Oudin, Ludovic, Thirel, Guillaume, and Collet, Lila

Thibault Lemaitre-Basset et al.


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Short summary
The increasing temperature will impact evaporation and water resources management. Hydrological models are fed with an estimation of the evaporative demand of the atmosphere, called potential evapotranspiration (PE). The first objective is to compute the future PE anomaly over France. The second objective is to determine the impact of the choice of the method to estimate PE. Our results show that all methods present similar future trends. No method really stands out from the others.