Analysis of leaf area index and fraction of PAR absorbed by vegetation products from the terra MODIS sensor: 2000-2005
Analysis of leaf area index and fraction of PAR absorbed by vegetation products from the terra MODIS sensor: 2000-2005
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DOI：
10.1109/tgrs.2006.871214
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发表时间：
2006-07
影响因子：
8.2
通讯作者：
Wenze Yang;D. Huang;B. Tan;J. Stroeve;N. Shabanov;Y. Knyazikhin;R. Nemani;R. Myneni
中科院分区：
文献类型：
--
作者：
Wenze Yang;D. Huang;B. Tan;J. Stroeve;N. Shabanov;Y. Knyazikhin;R. Nemani;R. Myneni
本文对两年收集3和5年收集4 Terra中分辨率成像光谱仪(MODIS)叶面积指数(LAI)和光合作用有效辐射(FPAR)数据集进行了分析，目的是了解关于版本(收集3与收集4)、算法(主与备份)、雪(无雪与地面雪)和云(无云与多云)条件下的产品质量。由于算法的改进和输入的改进，主要辐射传输算法的检索从集合3的55%增加到集合4的67%。采集4纠正了采集3产品中观测到的某些植被类型异常高的LAI/FPAR值。采集4存在着阔叶林反射率饱和和主要算法反演过少的问题。针叶LAI/FPAR场的虚假季节性是由于北方冬季可靠的输入数据和反演数据较少所致。利用基于归一化植被指数的后备归一化差分植被指数算法处理了约97%的积雪像素。同样，多云条件下的大多数检索都是从备份算法获得的。出于这些原因，建议用户参考LAI和FPAR产品的质量标志
The analysis of two years of Collection 3 and five years of Collection 4 Terra Moderate Resolution Imaging Spectroradiometer (MODIS) Leaf Area Index (LAI) and Fraction of Photosynthetically Active Radiation (FPAR) data sets is presented in this article with the goal of understanding product quality with respect to version (Collection 3 versus 4), algorithm (main versus backup), snow (snow-free versus snow on the ground), and cloud (cloud-free versus cloudy) conditions. Retrievals from the main radiative transfer algorithm increased from 55% in Collection 3 to 67% in Collection 4 due to algorithm refinements and improved inputs. Anomalously high LAI/FPAR values observed in Collection 3 product in some vegetation types were corrected in Collection 4. The problem of reflectance saturation and too few main algorithm retrievals in broadleaf forests persisted in Collection 4. The spurious seasonality in needleleaf LAI/FPAR fields was traced to fewer reliable input data and retrievals during the boreal winter period. About 97% of the snow covered pixels were processed by the backup Normalized Difference Vegetation Index-based algorithm. Similarly, a majority of retrievals under cloudy conditions were obtained from the backup algorithm. For these reasons, the users are advised to consult the quality flags accompanying the LAI and FPAR product