Comparing the Penman-Monteith equation and a modified Jarvis-Stewart model with an artificial neural network to estimate stand-scale transpiration and canopy conductance | Macquarie University ResearchOnline

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Comparing the Penman-Monteith equation and a modified Jarvis-Stewart model with an artificial neural network to estimate stand-scale transpiration and canopy conductance

Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.14/114392

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Title: Comparing the Penman-Monteith equation and a modified Jarvis-Stewart model with an artificial neural network to estimate stand-scale transpiration and canopy conductance
Related: Journal of hydrology, Vol. 373, No. 1-2 (2009), p.256-266
DOI: 10.1016/j.jhydrol.2009.04.036
Publisher: Elsevier
Date: 2009
FoR/RFCD Code(s): 040000 Earth Sciences 050000 Environmental Sciences 090000 Engineering
Author/Creator: Whitley, Rhys
Author/Creator: Medlyn, Belinda
Author/Creator: Zeppel, Melanie
Author/Creator: Macinnis-Ng, Catriona
Author/Creator: Eamus, Derek
Description: The responses of canopy conductance to variation in solar radiation, vapour pressure deficit and soil moisture have been extensively modelled using a Jarvis–Stewart (JS) model. Modelled canopy conductance has then often been used to predict transpiration using the Penman–Monteith (PM) model. We previously suggested an alternative approach in which the JS model is modified to directly estimate transpiration rather than canopy conductance. In the present study we used this alternative approach to model tree water fluxes from an Australian native forest over an annual cycle. For comparative purposes we also modelled canopy conductance and estimated transpiration via the PM model. Finally we applied an artificial neural network as a statistical benchmark to compare the performance of both models. Both the PM and modified JS models were parameterised using solar radiation, vapour pressure deficit and soil moisture as inputs with results that compare well with previous studies. Both models performed comparably well during the summer period. However, during winter the PM model was found to fail during periods of high rates of transpiration. In contrast, the modified JS model was able to replicate observed sapflow measurements throughout the year although it too tended to underestimate rates of transpiration in winter under conditions of high rates of transpiration. Both approaches to modelling transpiration gave good agreement with hourly, daily and total sums of sapflow measurements with the modified JS and PM models explaining 87% and 86% of the variance, respectively. We conclude that these three approaches have merit at different time-scales.
Description: 11 page(s)
Subject Keyword: 040000 Earth Sciences
Subject Keyword: 050000 Environmental Sciences
Subject Keyword: 090000 Engineering
Subject Keyword: canopy conductance
Subject Keyword: nocturnal flows
Subject Keyword: transpiration
Subject Keyword: Jarvis–Stewart model
Resource Type: journal article
Organisation: Macquarie University. Dept. of Biological Sciences

Identifier: http://hdl.handle.net/1959.14/114392
Identifier: ISSN:0022-1694
Identifier: mq-rm-2009002871
Language: eng
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