Rainfall interception and the coupled surface water and energy balance

Van Dijk, Albert I.J.M. and Gash, John H. and Van Gorsel, Eva and Blanken, Peter D. and Cescatti, Alessandro and Emmel, Carmen and Gielen, Bert and Harman, Ian N. and Kiely, Gerard and Merbold, Lutz and Montagnani, Leonardo and Moors, Eddy and Sottocornola, Matteo and Varlagin, Andrej and Williams, Christopher A. and Wohlfahrt, Georg (2015) Rainfall interception and the coupled surface water and energy balance. Agricultural and Forest Meteorology, 214-21. pp. 402-415. ISSN 0168-1923

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Abstract

Evaporation from wet canopies (. E) can return up to half of incident rainfall back into the atmosphere and is a major cause of the difference in water use between forests and short vegetation. Canopy water budget measurements often suggest values of E during rainfall that are several times greater than those predicted from Penman-Monteith theory. Our literature review identified potential issues with both estimation approaches, producing several hypotheses that were tested using micrometeorological observations from 128 FLUXNET sites world-wide. The analysis shows that FLUXNET eddy-covariance measurements tend to provide unreliable measurements of E during rainfall. However, the other micrometeorological FLUXNET observations do provide clues as to why conventional Penman-Monteith applications underestimate E. Aerodynamic exchange rather than radiation often drives E during rainfall, and hence errors in air humidity measurement and aerodynamic conductance calculation have considerable impact. Furthermore, evaporative cooling promotes a downwards heat flux from the air aloft as well as from the biomass and soil; energy sources that are not always considered. Accounting for these factors leads to E estimates and modelled interception losses that are considerably higher. On the other hand, canopy water budget measurements can lead to overestimates of E due to spatial sampling errors in throughfall and stemflow, underestimation of canopy rainfall storage capacity, and incorrect calculation of rainfall duration. There are remaining questions relating to horizontal advection from nearby dry areas, infrequent large-scale turbulence under stable atmospheric conditions, and the possible mechanical removal of splash droplets by such eddies. These questions have implications for catchment hydrology, rainfall recycling, land surface modelling, and the interpretation of eddy-covariance measurements.

Item Type:	Article
Additional Information:	Funding Information: This work used eddy-covariance data acquired by the FLUXNET community and in particular by the following networks: AmeriFlux (U.S. Department of Energy, Biological and Environmental Research, Terrestrial Carbon Program (DE-FG02-04ER63917 and DE-FG02-04ER63911)), AfriFlux, AsiaFlux, CarboAfrica, CarboEuropeIP, CarboItaly, CarboMont, ChinaFlux, Fluxnet-Canada (supported by CFCAS , NSERC , BIOCAP , Environment Canada , and NRCan ), GreenGrass, KoFlux, LBA, NECC, OzFlux, TCOS-Siberia, USCCC. We acknowledge the financial support to the eddy-covariance data harmonisation provided by CarboEuropeIP , FAO-GTOS-TCO , iLEAPS , Max Planck Institute for Biogeochemistry , National Science Foundation , University of Tuscia , Université Laval , Environment Canada and US Department of Energy and the database development and technical support from Berkeley Water Center, Lawrence Berkeley National Laboratory, Microsoft Research eScience, Oak Ridge National Laboratory, University of California – Berkeley and the University of Virginia. We thank Dr Beverly Law and other FLUXNET members for allowing the use of their data, and for their encouragement and useful suggestions along the way. We also thank an anonymous referee and Dr David Fitzjarrald for their constructive reviews. Publisher Copyright: © 2015 .
Uncontrolled Keywords:	/dk/atira/pure/subjectarea/asjc/2300/2306
Departments or Groups:
Depositing User:	Admin SSL
Date Deposited:	19 Oct 2022 23:04
Last Modified:	15 Aug 2023 19:50
URI:	http://repository-testing.wit.ie/id/eprint/3888

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