Path Length Correction for Improving Leaf Area Index Measurements Over Sloping Terrains: A Deep Analysis Through Computer Simulation

doi:10.1007/s10064-020-01959-9

CORC > 成都山地灾害与环境研究所 > 中国科学院水利部成都山地灾害与环境研究所

	Path Length Correction for Improving Leaf Area Index Measurements Over Sloping Terrains: A Deep Analysis Through Computer Simulation
	Yin Gaofei 5; Cao Biao 6; Li Jing 6; Fan Weiliang 1; Zeng Yelu 7; Xu Baodong 2; Zhao Wei 3,4
刊名	IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
	2020
卷号	58 期号:7 页码:DOI: 10.1007/s10064-020-01959-9
关键词	Computer simulation in situ measurement leaf area index (LAI) path length correction (PLC) topographic effect
ISSN号	0196-2892
DOI	10.1007/s10064-020-01959-9
通讯作者	Zhao, Wei(zhaow@imde.ac.cn)
产权排序	6
文献子类	Article
英文摘要	The in situ measurement of the leaf area index (LAI) from gap fraction is often affected by terrain slope. Path length correction (PLC) is commonly used to mitigate the topographic effect on the LAI measurements. However, the terrain-induced uncertainty and the accuracy improvement of the PLC for LAI measurements have not been systematically analyzed, hindering the establishment of an appropriate protocol for LAI measurements over mountainous regions. In this article, the above knowledge gap was filled using a computer simulation framework, which enables the estimated LAI before and after PLC to be benchmarked against the known and precise model truth. The simulation was achieved by using CANOPIX software and a dedicatedly designed ray-tracing method for continuous and discrete canopies, respectively. Simulations show that the slope distorts the angular pattern of the gap fraction, i.e., increasing the gap fraction in the down-slope direction and reducing it in the up-slope direction. The horizontally equivalent hemispheric gap fraction from the PLC can reconstruct the azimuthally symmetric angular pattern of the real horizontal surface. The azimuthally averaged gap fraction for sloping terrain can both be underestimated or overestimated depending on the LAI and can be successfully corrected through PLC. The topography-induced uncertainty in LAI measurements is found to be similar to 14.3% and >20% for continuous and discrete canopies, respectively. This uncertainty can be, respectively, reduced to similar to 1.8% and <7.3% after PLC, meeting the up-to-date uncertainty threshold of 15% established by the Global Climate Observing System (GCOS). Closer analysis shows that the topographic effect is influenced by fractional crown cover, and the largest uncertainty which corresponds to extensively clumping canopy can reach nearly up to 50%. The accuracy of the estimated LAI after PLC safely meets the GCOS uncertainty threshold even for this extreme case. This study demonstrates the necessity of a topographic correction for LAI measurements and the applicability of PLC for reconstructing the horizontally equivalent gap fraction and improving the LAI measurements over sloping terrains. The results of this article throw light on the design of a protocol for LAI measurements over mountainous regions.
电子版国际标准刊号	1435-9537
资助项目	National Natural Science Foundation of China[41531174] ; National Natural Science Foundation of China[41971282] ; National Natural Science Foundation of China[41601403] ; National Natural Science Foundation of China[41601478] ; National Natural Science Foundation of China[30-Y20A03-9003-17/18] ; Youth Innovation Promotion Association CAS[2016333]
WOS关键词	DIGITAL HEMISPHERICAL PHOTOGRAPHY ; SEASONAL-VARIATION ; GAP FRACTION ; BIOPHYSICAL PARAMETERS ; PRODUCT VALIDATION ; LAI ; MODEL ; REFLECTANCE ; FORESTS ; PHENOLOGY
WOS研究方向	Geochemistry & Geophysics ; Engineering ; Remote Sensing ; Imaging Science & Photographic Technology
语种	英语
出版者	IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
WOS记录号	WOS:000560635100001
资助机构	National Natural Science Foundation of China ; Youth Innovation Promotion Association CAS
内容类型	期刊论文
源URL	[http://ir.imde.ac.cn/handle/131551/35173]
专题	中国科学院水利部成都山地灾害与环境研究所
通讯作者	Zhao Wei
作者单位	1.Zhejiang A&F Univ, Sch Environm & Resources Sci, Linan 311300, Peoples R China; 2.Huazhong Agr Univ, Coll Resource & Environm, Macro Agr Res Inst, Wuhan 430070, Peoples R China; 3.Chinese Acad Sci, Inst Mt Hazards & Environm, Chengdu 610010, Peoples R China; 4.Henan Univ, Minist Educ, Key Lab Geospatial Technol Middle & Lower Yellow, Kaifeng 475004, Peoples R China 5.Southwest Jiaotong Univ, Fac Geosci & Environm, Chengdu 610031, Peoples R China; 6.Chinese Acad Sci, Inst Remote Sensing & Digital Earth, State Key Lab Remote Sensing Sci, Beijing 100101, Peoples R China; 7.Carnegie Inst Sci, Dept Global Ecol, Stanford, CA 94305 USA;
推荐引用方式 GB/T 7714	Yin Gaofei,Cao Biao,Li Jing,et al. Path Length Correction for Improving Leaf Area Index Measurements Over Sloping Terrains: A Deep Analysis Through Computer Simulation[J]. IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING,2020,58(7):DOI: 10.1007/s10064-020-01959-9.
APA	Yin Gaofei.,Cao Biao.,Li Jing.,Fan Weiliang.,Zeng Yelu.,...&Zhao Wei.(2020).Path Length Correction for Improving Leaf Area Index Measurements Over Sloping Terrains: A Deep Analysis Through Computer Simulation.IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING,58(7),DOI: 10.1007/s10064-020-01959-9.
MLA	Yin Gaofei,et al."Path Length Correction for Improving Leaf Area Index Measurements Over Sloping Terrains: A Deep Analysis Through Computer Simulation".IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 58.7(2020):DOI: 10.1007/s10064-020-01959-9.