Preprints
https://doi.org/10.5194/hess-2022-164
https://doi.org/10.5194/hess-2022-164
 
24 May 2022
24 May 2022
Status: this preprint is currently under review for the journal HESS.

Improving the calibration-free complementary evaporation principle by linking with the Budyko framework

Daeha Kim1, Minha Choi2, and Jong Ahn Chun3 Daeha Kim et al.
  • 1Department of Civil Engineering, Jeonbuk National University, Jeonju, Jeollabuk-do, 54896, South Korea
  • 2Department of Water Resources, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, South Korea
  • 3Prediction Research Department, APEC Climate Center, Busan, 48058, South Korea

Abstract. While it has performed well in predicting terrestrial evapotranspiration (ETa) in many gauged locations over the world, the calibration-free complementary relationship (CR) depends on a questionable assumption that the Priestley-Taylor coefficient (αe) is spatially constant over an extensive area. In this work, we evaluated the predictive performance of this convenient method, which only requires atmospheric inputs, against in-situ flux observations and water balance estimates (ETwb) in Australia. We found that the CR method with a spatially constant αe derived from fractional wet areas did not perform as highly as previous studies would suggest, underperforming three advanced ETa models in closing basin-scale water balance. This problem was remedied by linking the CR method with a traditional Budyko equation that allowed upscaling of optimal αe values from gauged basins to ungauged locations. The CR method with the αe upscaled by the atmospheric inputs and the mean precipitation (P) better reproduced the grid ETwb available over the entire continent, and outperformed the three ETa models. This study suggests that the fixed αe could lead the CR method to biased ETa estimates, and it needs to be constrained by climate conditions to better close local water budgets.

Daeha Kim et al.

Status: open (until 22 Jul 2022)

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Daeha Kim et al.

Daeha Kim et al.

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Short summary
In this work, we improved a practical method that predicts the evaporation rates on land surfaces (ETa) in Australia. By combing with a traditional equation that describes partitioning of precipitation into ETa and streamflow, we could approximately identify the key parameter of the ETa method at ungauged locations. The combined method outperformed in reproducing water-balance ETa estimates across the Australian continent, while only requiring atmospheric inputs.