
%0 Journal Article
%A Wang, Ying Ping 
%T A comparison of three different canopy radiation models commonly used in plant modelling
%J Functional Plant Biology
%D 2003/02/18
%V 30
%N 2
%P 143-152
%K radiation model, photosynthesis, Beer&#39;s law, two-stream approximation, canopy, latent, sensible heat, albedo.
%R https://doi.org/10.1071/FP02117
%U https://www.publish.csiro.au/paper/FP02117 
%X Three radiation models are compared. They are the two-stream approximation, Goudriaan&#39;s radiation model and Beer&#39;s law. If direct beam and diffuse radiation are considered separately with the appropriate extinction coefficients, Beer&#39;s law can be used to estimate the fraction of absorbed visible radiation quite accurately, as compared with the other two models. However, Beer&#39;s law always overestimates the fraction of absorbed near-infrared radiation because of the significant loss of scattered radiation in the near-infrared radiation waveband; the error can be up to 50%, compared with the two-stream approximation. The error is systematic and is not reduced by integrating over a day or longer. It can be even larger if absorption of direct beam and diffuse radiation are not considered separately. Compared with the two-stream approximation, Goudriaan&#39;s model underestimates the amount of absorbed visible and near-infrared radiation, and consequently net photosynthesis, and overestimates sensible heat fluxes of the canopy when Goudriaan&#39;s model is used to estimate the amount of radiation absorbed by sunlit and shaded leaves within a canopy in the CSIRO Biosphere Model. However, the mean differences in the calculated hourly fluxes of net canopy photosynthesis, latent and sensible heat are less than 5% for a wheat crop during the whole growing season. 
