%0 Journal Article
%A LI Li
%A FAN Wenjie
%A DU Yongming
%A TANG Yong
%A XIN Xiaozhou
%A ZHANG Hailong
%A LIU Qinhuo
%T A Characteristic Study of Crop Canopy Direct and Diffuse Fraction of Absorbed Photosynthetically Active Radiation Based on SAIL Model Simulation
%D 2015
%R
%J Acta Scientiarum Naturalium Universitatis Pekinensis
%P 99-108
%V 51
%N 1
%X In order to discriminate the canopyâ€™s absorption of direct solar radiation and scattered radiation and the influence to total FPAR (fraction of absorbed photosynthetically active radiation), the SAIL (scattering by arbitrarily inclined leaves) model is used to simulate the direct FPAR, scattering of FPAR and total FPAR under different weather condition. The main factors influencing the change of total FPAR and the difference between direct FPAR and diffuse FPAR are analysised. The results show that with the change of LAI, FPAR also has the saturation phenomenon. When the visibility is set as 5, 15 and 30 km, the contribution of scattering of FPAR on the total FPAR is 52.6%, 29.3% and 21.7%. The error between total FPAR and direct FPAR is reduced with the increasing of visibility and increased with the reducing of LAI. The maximum relative error is 13.2%. With the change of the solar zenith, the maximum relative error is 10.29% between direct FPAR and total FPAR. From the simulation analyses, it can be see that direct and diffuse FPAR are different with the changes of environment variables. So when modeling of FPAR, the diffuse part can not be ignored. Direct FPAR and diffuse FPAR must be modeled respectively. The total FPAR need to be calculated by the proportion of scattered radiation which is determined by the weather condition.
%U https://xbna.pku.edu.cn/EN/abstract/article_2324.shtml