AN ANALYTICAL AND COMPUTATIONALLY EFFICIENT REFLECTANCE MODEL FOR LEAF CANOPIES

	AN ANALYTICAL AND COMPUTATIONALLY EFFICIENT REFLECTANCE MODEL FOR LEAF CANOPIES
	QIN, WH ; JUPP, DLB
刊名	AGRICULTURAL AND FOREST METEOROLOGY
	1993-09-01
卷号	66 期号:1-2 页码:31-64
ISSN号	0168-1923
英文摘要	An explicit analytical model for calculating vegetation canopy reflectance is developed in this paper, based on radiative transfer theory through separating the roles of incident direct and diffuse radiation, singly and multiply scattered radiation by foliage and soil. Using principles of scattering from a point source, the contributions of diffuse sky radiation to both first-order and multiple scattering reflectance are accurately specified. In addition, this analytical model incorporates the effects of nonrandom spatial dispersion of foliage, noncircular shape and nonhorizontal orientation of leaves on the canopy hotspot and then on reflectance distributions. Although the reflectance by multiple scattering is simply estimated with the two-stream approximation (Nilson, 1991), the angular distributions of canopy reflectance produced by the model agree well with those measured above soybean and wheat canopies. Some original results from model sensitivity analysis are sketched as follows: (1) leaf shape and orientation have a considerable influence on the canopy hotspot except for planophile canopies or in near nadir viewing directions. The contributions of soil reflectance and multiple scattering increase with the modal inclination angle of leaves; (2) the foliage spatial dispersion pattern changes the magnitude and angular distribution of the canopy reflectance strongly in the RED band; (3) when the ratio of diffuse sky radiation to the total incident radiation is less than 20%, its contribution to canopy reflectance is less than 6% and 8% on average for RED and NIR bands, respectively. This provides a means to approximately calculate the two components signifying the role of diffuse sky radiation and then to conditionally simplify this reflectance model, and therefore improve its practical applicability; (4) the sensitive regions of different structural parameters are usually different and generally change with waveband and leaf orientation. This implies that only by using the reflectance data in its sensitive region, can a specified parameter be accurately estimated by model inversion. Finally, further improvements needed for analytical approaches are briefly discussed.
WOS关键词	CONIFER FOREST CANOPY ; BIDIRECTIONAL REFLECTANCE ; VEGETATION CANOPIES ; RADIATIVE-TRANSFER ; PLANT CANOPY ; SCATTERING ; WOODLANDS
WOS研究方向	Agriculture ; Forestry ; Meteorology & Atmospheric Sciences
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:A1993LX12800003
内容类型	期刊论文
源URL	[http://ir.igsnrr.ac.cn/handle/311030/56501]
专题	中国科学院地理科学与资源研究所
作者单位	1.CHINESE ACAD SCI,INST GEOG,BEIJING 100101,PEOPLES R CHINA 2.CSIRO,DIV WATER RESOURCES,CANBERRA,ACT 2601,AUSTRALIA
推荐引用方式 GB/T 7714	QIN, WH,JUPP, DLB. AN ANALYTICAL AND COMPUTATIONALLY EFFICIENT REFLECTANCE MODEL FOR LEAF CANOPIES[J]. AGRICULTURAL AND FOREST METEOROLOGY,1993,66(1-2):31-64.
APA	QIN, WH,&JUPP, DLB.(1993).AN ANALYTICAL AND COMPUTATIONALLY EFFICIENT REFLECTANCE MODEL FOR LEAF CANOPIES.AGRICULTURAL AND FOREST METEOROLOGY,66(1-2),31-64.
MLA	QIN, WH,et al."AN ANALYTICAL AND COMPUTATIONALLY EFFICIENT REFLECTANCE MODEL FOR LEAF CANOPIES".AGRICULTURAL AND FOREST METEOROLOGY 66.1-2(1993):31-64.