焦子锑等：An Anisotropic Flat Index (AFX) to derive BRDF archetypes from MODIS

An Anisotropic Flat Index (AFX) to derive BRDF archetypes from MODIS
作者:Jiao, ZT (Jiao, Ziti)[ 1,2,3 ] ; Hill, MJ (Hill, Michael J.)[ 4 ] ; Schaaf, CB (Schaaf, Crystal B.)[ 5 ] ; Zhang, H (Zhang, Hu)[ 1,2,3 ] ; Wang, ZS (Wang, Zhuosen)[ 5 ] ; Li, XW (Li, Xiaowen)[ 1,2,3 ]
REMOTE SENSING OF ENVIRONMENT
卷: 141  页: 168-187
DOI: 10.1016/j.rse.2013.10.017
出版年: FEB 5 2014

摘要
Spectral vegetation indices can be generalized as a function of surface reflectance with respect to wavelength. However, there is significant information on vegetation structure embedded in the anisotropic effects of the target. In this study, we describe and characterize a new vegetation index, the Anisotropic Flat Index (AFX) that captures this anisotropic scattering information and can be derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF) product suite (MOD43A1). The AFX is created by normalization of net scattering magnitude (obtained from volumetric and geometric-optical scattering) with the isotropic scattering. The AFX summarizes the variability of basic dome-bowl anisotropic reflectance patterns of the terrestrial surface. A classification scheme for BRDF typology is created based on AFX archetypes that capture characteristic BRDF shape types. This study fully characterizes AFX in a number of steps. First, sensitivity to random noise and observation geometries is explored by comparing the AFX with other variables derived from field measurements that comprehensively sample the viewing hemisphere. Second, AFX is compared with normalized difference vegetation index (NDVI) values using field measurements from many ground campaigns, as well as global MODIS observations from EOS Land Validation Core Sites (LVCS). Third, a BRDF typology is developed by classification of an a priori database of BRDF archetypes from field measurements, and from MODIS observations that cover the full range of vegetation types from grasslands to closed forest (MCD43A). Fourth, the response of AFX to the parameter variability of canopy architectures and background optical properties for three vegetation types with discontinuous woody canopies is investigated through the use of a 5-Scale BRDF model simulation. Finally, global BRDF archetypes are mapped and discussed through the use of a global high-quality MODIS BRDF/albedo gap filled product (MCD43GF). The results show that the AFX summarizes BRDF archetypes and provides additional information on vegetation structure and other anisotropic reflectance characteristics of the land surface. (C) 2013 Elsevier Inc. All rights reserved.

通讯作者地址: Jiao, ZT (通讯作者)
Beijing Normal Univ, State Key Lab Remote Sensing Sci, Beijing 100875, Peoples R China.
地址:
[ 1 ] Beijing Normal Univ, State Key Lab Remote Sensing Sci, Beijing 100875, Peoples R China
[ 2 ] Beijing Normal Univ, Sch Geog, Beijing 100875, Peoples R China
[ 3 ] Beijing Normal Univ, Beijing Key Lab Environm Remote Sensing & Digital, Beijing 100875, Peoples R China
[ 4 ] Univ N Dakota, Dept Earth Syst Sci & Policy, Grand Forks, ND 58202 USA
[ 5 ] Univ Massachusetts, Sch Environm, Boston, MA 02125 USA