|Titre||New calculation methods of diurnal distribution of solar radiation and its interception by canopy over complex terrain|
|Auteur||Wang, S; Chen, W; Cihlar, J|
|Source||Ecological Modelling vol. 155, no. 43134, 2002 p. 191-204, https://doi.org/10.1016/S0304-3800(02)00122-9|
|Séries alt.||Ressources naturelles Canada, Contribution externe 20181320|
|Document||publication en série|
|Media||papier; en ligne; numérique|
|Programme||Géosciences de changements climatiques|
|Résumé||(disponible en anglais seulement)|
The prescription of diurnal radiation distribution and the consideration of topographic impact on canopy radiation interception are often required in ecological
modelling studies. The most commonly used methods in current models are the sine-curve assumption for diurnal radiation distribution and the topographic geometric projection for canopy radiation interception. In this study, the defects of these two
methods are examined and two new methods are proposed. The new method for prescribing the diurnal radiation distribution is based on the assumption that the direct normal radiation and diffusive radiation follow the sine-curve of solar zenith angle.
This improvement is particularly important to the modelling strategies of separating canopy leaves into sunlit and shaded. It can also be used to extrapolating daily data to hourly values so that the short time step models can be applied when only
daily data are available. The new method for calculating canopy radiation interception over inclined surfaces is based on the hypothesis that the topographic variation of canopy radiation interception is caused by the variation of sunlit/shaded leaf
area index. This new method gives the same amount of total radiant energy interception as the geometric projection method, but it may lead to very different impact of topography on ecological processes. The topographic variation of canopy
photosynthesis was investigated by using this new approach and compared with that obtained by using the direct geometric projection method. The two new approaches proposed in this study are more physically realistic in regenerating the natural
processes. The improvements can benefit ecological models on temporal integration studies as well as spatial scale analysis over complex terrain.