Estimation of canopy clumping index from MISR and MODIS sensors using the normalized difference hotspot and darkspot (NDHD) method: The influence of BRDF models and solar zenith angle
Estimation of canopy clumping index from MISR and MODIS sensors using the normalized difference hotspot and darkspot (NDHD) method: The influence of BRDF models and solar zenith angle
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使用归一化差异热点和暗点 (NDHD) 方法估计 MISR 和 MODIS 传感器的冠层丛集指数：BRDF 模型和太阳天顶角的影响
DOI：
10.1016/j.rse.2016.10.039
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发表时间：
2016-12
影响因子：
13.5
通讯作者：
Fang Hongliang
中科院分区：
文献类型：
--
作者：
Wei Shanshan;Fang Hongliang
丛生指数(CI)描述了树叶的空间分布格局，是描述陆地生态系统和模拟陆面过程的重要参数。全球和区域尺度的CI地图已经由POLDER、MODIS和MISR传感器生成，该地图基于先前研究的归一化热点与暗点指数差(NDHD)之间的经验关系。然而，不同的双向反射分布函数(BRDF)模型和太阳天顶角(SZA)，热点、暗斑和CI值可能会有很大差异。在这项研究中，我们评估了不同配置的BRDF模型和SZA值对使用NDHD方法进行CI估计的影响。从MISR和MODIS得到的CI图与Valeri站点的参考数据进行了比较。结果表明，对于中等到最小的丛生植被(CI0.5)，观测SZA反演的CI值与野外实测值吻合较好，SZA=°低估，SZA=0.60°高估。对于高聚集区(CI=0.5)和植被稀疏区(FCOVER<；=25%)，推荐使用60°SZA的Ross-Li模型进行CI估计。最佳NDHD配置被用来从MODIS BRDF数据估计15年的时间序列CI。时间序列CI表现出合理的季节变化轨迹，且与MODIS叶面积指数(LAI)变化一致。这项研究使NDHD方法能够更好地用于CI估计，并可为CI有效性的研究提供有益的参考。
Clumping index (CI) describes the spatial distribution pattern of foliage, and is a critical parameter to characterize the terrestrial ecosystem and model land-surface processes. Global and regional scale CI maps have been generated from POLDER, MODIS, and MISR sensors based on an empirical relationship with the normalized difference between hotspot and darkspot (NDHD) index by previous studies. However, the hotspot, darkspot, and CI values can be considerably different from different bidirectional reflectance distribution function (BRDF) models and solar zenith angles (SZA). In this study, we evaluated the effects of different configurations of BRDF models and SZA values on CI estimation using the NDHD method. CI maps derived from MISR and MODIS were compared with reference data at the VALERI sites. Results show that for moderate to least clumped vegetation (CI > 0.5), CI values retrieved with the observational SZA agree well with field measurements, while SZA = 0° underestimates, and SZA = 60° overestimates. For highly clumped (CI < 0.5) and sparsely vegetated areas (FCOVER < 25%), the Ross-Li model with 60° SZA is recommended for CI estimation. The best NDHD configuration was used to estimate a 15-year time series CI from MODIS BRDF data. The time series CI shows a reasonable seasonal trajectory, and varies consistently with the MODIS leaf area index (LAI). This study enables better usage of the NDHD method for CI estimation, and can be a useful reference for research on CI validation.
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影响因子：
6.2
作者：
CHEN, JM;BLACK, TA
通讯作者：
BLACK, TA
参考站点上 POLDER、MODIS 和 MISR 卫星数据的丛集指数估计值的相互比较
DOI：
10.1016/j.isprsjprs.2014.11.004
发表时间：
2015-03
期刊：
. ISPRS Journal of Photogrammetry and Remote Sensing
影响因子：
--
作者：
Wardlaw, T. J.;Fang, H.;Matteucci, G.;Longdoz, B.
通讯作者：
Longdoz, B.
影响因子：
13.5
作者：
J. Armston;P. Scarth;S. Phinn;T. Danaher
通讯作者：
J. Armston;P. Scarth;S. Phinn;T. Danaher
DOI：
10.1109/tgrs.2006.872529
发表时间：
2006-07-01
影响因子：
8.2
作者：
Morisette, Jeffrey T.;Baret, Frederic;Cook, Robert
通讯作者：
Cook, Robert
影响因子：
3.4
作者：
J. Pisek;J. Chen;T. Nilson
通讯作者：
J. Pisek;J. Chen;T. Nilson