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Rainfall interception modelling: is the wet bulb approach adequate to estimate mean evaporation rate from wet/saturated canopies in all forest types?

Pereira, F.L.; Valente, F.; David, J.S.; Jackson, N.; Minunno, F.; Gash, J.H.. 2016 Rainfall interception modelling: is the wet bulb approach adequate to estimate mean evaporation rate from wet/saturated canopies in all forest types? Journal of Hydrology, 534. 606-615. 10.1016/j.jhydrol.2016.01.035

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Abstract/Summary

The Penman–Monteith equation has been widely used to estimate the maximum evaporation rate (E) from wet/saturated forest canopies, regardless of canopy cover fraction. Forests are then represented as a big leaf and interception loss considered essentially as a one-dimensional process. With increasing forest sparseness the assumptions behind this big leaf approach become questionable. In sparse forests it might be better to model E and interception loss at the tree level assuming that the individual tree crowns behave as wet bulbs (‘‘wet bulb approach”). In this study, and for five different forest types and climate conditions, interception loss measurements were compared to modelled values (Gash’s interception model) based on estimates of E by the Penman–Monteith and the wet bulb approaches. Results show that the wet bulb approach is a good, and less data demanding, alternative to estimate E when the forest canopy is fully ventilated (very sparse forests with a narrow canopy depth). When the canopy is not fully ventilated, the wet bulb approach requires a reduction of leaf area index to the upper, more ventilated parts of the canopy, needing data on the vertical leaf area distribution, which is seldom-available. In such cases, the Penman–Monteith approach seems preferable. Our data also show that canopy cover does not per se allow us to identify if a forest canopy is fully ventilated or not. New methodologies of sensitivity analyses applied to Gash’s model showed that a correct estimate of E is critical for the proper modelling of interception loss.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.jhydrol.2016.01.035
CEH Sections: Directors, SPCs
CEH fellows
ISSN: 0022-1694
Additional Keywords: interception loss, surface temperature, Gash model, sparse forest, Penman–Monteith
NORA Subject Terms: Hydrology
Agriculture and Soil Science
Date made live: 15 Feb 2016 11:15 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/512968

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