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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 19, issue 2
Hydrol. Earth Syst. Sci., 19, 997-1014, 2015
https://doi.org/10.5194/hess-19-997-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Hydrol. Earth Syst. Sci., 19, 997-1014, 2015
https://doi.org/10.5194/hess-19-997-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 24 Feb 2015

Research article | 24 Feb 2015

Sensitivity of potential evaporation estimates to 100 years of climate variability

R. P. Bartholomeus1, J. H. Stagge2, L. M. Tallaksen2, and J. P. M. Witte1,3 R. P. Bartholomeus et al.
  • 1KWR Watercycle Research Institute, P.O. Box 1072, 3430 BB Nieuwegein, the Netherlands
  • 2Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, 0316 Oslo, Norway
  • 3VU University, Institute of Ecological Science, Department of Systems Ecology, de Boelelaan 1085, 1081 HV Amsterdam, the Netherlands

Abstract. Hydrological modeling frameworks require an accurate representation of evaporation fluxes for appropriate quantification of, e.g., the water balance, soil moisture budget, recharge and groundwater processes. Many frameworks have used the concept of potential evaporation, often estimated for different vegetation classes by multiplying the evaporation from a reference surface ("reference evaporation") by crop-specific scaling factors ("crop factors"). Though this two-step potential evaporation approach undoubtedly has practical advantages, the empirical nature of both reference evaporation methods and crop factors limits its usability in extrapolations under non-stationary climatic conditions. In this paper, rather than simply warning about the dangers of extrapolation, we quantify the sensitivity of potential evaporation estimates for different vegetation classes using the two-step approach when calibrated using a non-stationary climate. We used the past century's time series of observed climate, containing non-stationary signals of multi-decadal atmospheric oscillations, global warming, and global dimming/brightening, to evaluate the sensitivity of potential evaporation estimates to the choice and length of the calibration period. We show that using empirical coefficients outside their calibration range may lead to systematic differences between process-based and empirical reference evaporation methods, and systematic errors in estimated potential evaporation components. Quantification of errors provides a possibility to correct potential evaporation calculations and to rate them for their suitability to model climate conditions that differ significantly from the historical record, so-called no-analog climate conditions.

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We used the past century’s time series of observed climate, containing non-stationary signals of atmospheric oscillations, global warming, and global dimming/brightening, to quantify possible systematic errors that may be introduced in estimates of potential evaporation and in hydrological modeling studies due to straightforward application of i) the common two-step approach for potential evaporation specifically, and ii) fixed instead of time-variant model parameters in general.
We used the past century’s time series of observed climate, containing non-stationary signals...
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