Print Email Facebook Twitter HESS Opinions “A perspective on isotope versus non-isotope approaches to determine the contribution of transpiration to total evaporation” Title HESS Opinions “A perspective on isotope versus non-isotope approaches to determine the contribution of transpiration to total evaporation” Author Sutanto, S.J. Van den Hurk, B. Dirmeyer, P.A. Seneviratne, S.I. Röckmann, T. Trenberth, K.E. Blyth, E.M. Wenninger, J. Hoffmann, G. Faculty Civil Engineering and Geosciences Department Water Management Date 2014-08-04 Abstract Current techniques to disentangle the evaporative fluxes from the continental surface into a contribution evaporated from soils and canopy, or transpired by plants, are under debate. Many isotope-based studies show that transpiration contributes generally more than 70% to the total evaporation, while other isotope-independent techniques lead to considerably smaller transpiration fractions. This paper provides a perspective on isotope-based versus non-isotope-based partitioning studies. Some partitioning results from isotope-based methods, hydrometric measurements, and modeling are presented for comparison. Moreover, the methodological aspects of the partitioning analysis are considered, including their limitations, and explanations of possible discrepancies between the methods are discussed. We suggest sources of systematic error that may lead to biases in the results, e.g., instruments inaccuracy, assumptions used in analyses, and calibration parameters. A number of comparison studies using isotope-based methods and hydrometric measurements in the same plants and climatic conditions are consistent within the errors; however, models tend to produce lower transpiration fractions. The relatively low transpiration fraction in current state-of-the-art land-surface models calls for a reassessment of the skill of the underlying model parameterizations. The scarcity of global evaporation data makes calibration and validation of global isotope-independent and isotope-based results difficult. However, isotope-enabled land-surface and global climate modeling studies allow for the evaluation of the parameterization of land-surface models by comparing the computed water isotopologue signals in the atmosphere with the available remote sensing and flux-based data sets. Future studies that allow for this evaluation could provide a better understanding of the hydrological cycle in vegetated regions. To reference this document use: http://resolver.tudelft.nl/uuid:9cabca5e-64ab-42b8-856f-cfb4d087e942 DOI https://doi.org/10.5194/hess-18-2815-2014 Publisher European Geosciences Union ISSN 1027-5606 Source http://www.hydrol-earth-syst-sci.net/18/2815/2014/ Source Hydrology and Earth System Sciences, 18 (8), 2014 Part of collection Institutional Repository Document type journal article Rights © 2014 The Author(s)CC Attribution 3.0 License Files PDF Wenninger_2014.pdf 1.37 MB Close viewer /islandora/object/uuid:9cabca5e-64ab-42b8-856f-cfb4d087e942/datastream/OBJ/view