Angular normalization of GOME‐2 Sun‐induced chlorophyll fluorescence observation as a better proxy of vegetation productivity
Angular normalization of GOME‐2 Sun‐induced chlorophyll fluorescence observation as a better proxy of vegetation productivity
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DOI：
10.1002/2017gl073708
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发表时间：
2017-06
影响因子：
5.2
通讯作者：
Liming He;Jing M. Chen;Jane Liu;G. Mo;J. Joiner
中科院分区：
文献类型：
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作者：
Liming He;Jing M. Chen;Jane Liu;G. Mo;J. Joiner
太阳诱导叶绿素荧光（SIF）已被认为是陆地总初级生产力（GPP）的一个有前途的代理。由于太阳-卫星视图观测几何结构的变化，可能会引起SIF观测中不必要的变化，因此使用遥感SIF进行GPP估计存在相当大的不确定性。在这项研究中，我们将晴天的远红外全球臭氧监测实验-2 SIF观测结果标准化为热点方向（SIFh），以表示阳光照射的叶子，并计算阳光照射和阴影叶子的SIF加权和（SIFt），以表示树冠。我们发现，SIF h与基于过程的生态系统模型模拟的日照GPP相关性更好，SIF t与模拟的总GPP相关性比原始SIF观测更好。使用SIFh和SIFt时，决定系数（R2）分别增加了0.04 ± 0.03和0.07 ± 0.04。落叶阔叶林的R2增加最显著（SIFt为0.09 ± 0.04，SIFh为0.05 ± 0.03）。
Sun‐induced chlorophyll fluorescence (SIF) has been regarded as a promising proxy for gross primary productivity (GPP) over land. Considerable uncertainties in GPP estimation using remotely sensed SIF exist due to variations in the Sun‐satellite view observation geometry that could induce unwanted variations in SIF observation. In this study, we normalize the far‐red Global Ozone Monitoring Experiment‐2 SIF observations on sunny days to hot spot direction (SIFh) to represent sunlit leaves and compute a weighted sum of SIF (SIFt) from sunlit and shaded leaves to represent the canopy. We found that SIFh is better correlated with sunlit GPP simulated by a process‐based ecosystem model and SIFt is better correlated with the simulated total GPP than the original SIF observations. The coefficient of determination (R2) are increased by 0.04 ± 0.03, and 0.07 ± 0.04 on a global average using SIFh and SIFt, respectively. The most significant increases of the R2 (0.09 ± 0.04 for SIFt and 0.05 ± 0.03 for SIFh) appear in deciduous broadleaf forests.