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www.geosci-model-dev-discuss.net/4/1793/2011/
doi:10.5194/gmdd-4-1793-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Efficient modeling of sun/shade canopy radiation dynamics explicitly accounting for scattering
1Lund University, Lund, Sweden
2Swansea University, Swansea, UK
3International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria
Abstract. The separation of global radiation (Rg) into its direct (Rb) and diffuse constituents (Rd) is important when modeling plant photosynthesis because a high Rd:Rg ratio has been shown to enhance Gross Primary Production (GPP). To include this effect in vegetation models, the plant canopy must be separated into sunlit and shaded leaves, for example using an explicit 3-dimensional ray tracing model. However, because such models are often too intractable and computationally expensive for theoretical or large scale studies simpler sun-shade approaches are often preferred. A widely used and computationally efficient sun-shade model is a model originally developed by Goudriaan (1977) (GOU), which however does not explicitly account for radiation scattering.
Here we present a new model based on the GOU model, but which in contrast explicitly simulates radiation scattering by sunlit leaves and the absorption of this radiation by the canopy layers above and below (2-stream approach). Compared to the GOU model our model predicts significantly different profiles of scattered radiation that are in better agreement with measured profiles of downwelling diffuse radiation. With respect to these data our model's performance is equal to a more complex and much slower iterative radiation model while maintaining the simplicity and computational efficiency of the GOU model.
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Notice on Discussion StatusCitation: Bodin, P. and Franklin, O.: Efficient modeling of sun/shade canopy radiation dynamics explicitly accounting for scattering, Geosci. Model Dev. Discuss., 4, 1793-1808, doi:10.5194/gmdd-4-1793-2011, 2011. Bibtex EndNote Reference Manager XML
