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Theoretical Simulation of Vegetation Canopy's Optical Characteristics with Two-layer Structure |
SHEN Yan 1,2 , NIU Zheng 2, MIAO Qi-long 1, WANG Wen 3 |
1.College of Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China;
2.The State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing Applications, Chinese Academy of Sciences, Beijing 100101, China;
3.College of Environment, Renmin University of China, Beijing 100872, China |
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Abstract Several vegetation canopies have a two-layer structure. In forests a moss or lichen layer is on ground surface under grass layer. In field crops a thin weed layer on ground under crop canopy is rather common. Both, optical and structural parameters of these two layers may be rather different and if we use homogeneous canopy reflectance (CR) models for the calculation of the directional reflectance of such canopies using mean (weighted mean) values of phytometrical and optical parameters we may have systematic errors in reflectance values. In this article, based on the two-layer canopy reflectance model ACRM, canopy reflectance angular distributions with wavelength 820 nm and 1 600 nm are simulated under the influence of LAI (leaf area index), Cw (water content)and N (a structural parameter). Research results indicate that the hot spot effect can be simulated precisely. The sensitivity of canopy reflectance angular distributing to LAI is less than to LAI-Cw and LAI-N. Reflectance angular distribution at 1 600 nm wavelength is strongly related to LAI and Cw while reflectance at 820nm is appreciable larger than the one at 1 600 nm under LAI and N effect. Besides, using information contained in near-infrared (820 nm)and short-wave infrared (1 600 nm) canopy reflectance we proposed a soil-adjusted water index which is employed to retrieve the canopy water content is also greatly influenced by canopy structure. Canopy structure is worth considering in the process of model selection henceforth.
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Received: 03 November 2004
Published: 17 November 2011
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〔1〕 Verhoef W. Light Scattering by Leaf Layers with Application to Canopy Reflectance Modeling: The SAIL Model〔J〕. Remote Sensing of Environment, 1984,16:125~141.〔2〕 Jacquemoud S, Baret F. PROSPECT: A Model of Leaf Opt-ical Properties〔J〕. Remote Sensing of Environment, 1990,34:75~91. 〔3〕 Dawon T P, Curran P J, North P R J, et al. LIBERTY: Modeling the Effects of Leaf Biochemistry on Reflectance Spectra〔J〕. Remote Sensing of Environment, 1998,65:50~60. 〔4〕 Kuusk A. A Two-layer Canopy Reflectance Model〔J〕. Journal of Quantitative Spectroscopy & Radiative Transfer. 2001,71:1~9. 〔5〕 沈艳,牛铮,颜春燕. 植被叶片及冠层层次含水量估算模型的建立〔J〕.应用生态学报,2005,16:1218~1223. |
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