Retrieval of sun-induced fluorescence using advanced spectral fitting methods
Retrieval of sun-induced fluorescence using advanced spectral fitting methods
复制标题
DOI：
10.1016/j.rse.2015.08.022
复制
发表时间：
2015-11-01
影响因子：
13.5
通讯作者：
Colombo, R.
中科院分区：
文献类型：
--
作者：
Cogliati, S.;Verhoef, W.;Colombo, R.
荧光探测器(FLEX)卫星任务是欧空局第八个地球探测器计划的候选卫星，它显然是为探测植物发出的太阳诱导荧光而优化的。它将允许在O-2-B(687 Nm)和O-2-A(760 Nm)波段附近进行一致的测量，分别与红色和远红荧光发射峰、光化学反射指数和树冠的结构-化学状态变量有关。利用强大的光谱拟合技术，可以准确地提取叠加在地表反射辐射上的太阳诱导荧光信号。在这个框架下，本研究提出了一套针对FLEX进行优化的荧光检索算法。研究了两种主要的反演方法：i)对氧吸收带的荧光进行光谱拟合的优化；ii)将光谱拟合扩展到更宽的光谱窗口，以便在670~780 nm范围内反演完整的荧光光谱。通过使用耦合示波器和MODTRAN5程序得到的大气-地表辐射传输模拟，对算法的精度进行了评估。模拟的数据集考虑了更现实的条件，因为它包括方向效应，并且大气层顶部的辐射光谱被重新采样到计划作为FLEX上的主要仪器的荧光成像光谱仪(FLOIS)的当前规格。O-2-A波段的反演精度受方向效应的影响较大，方向效应越小，反演精度越好。然而，性能最好的算法提供了相似的性能，均方根误差(RRMSE)在O-2-A波段为0.044 mW m(-2)sr(-1)nm(-1)(6.2%)，0.018 mW m(-2)sr(-1)nm(-1)(2.9%)，以及6225 mW m(-2)sr(-1)(6.4%)用于光谱积分荧光发射。这些有希望的成果不仅扩展了对有限吸收带的荧光研究，而且扩展了荧光研究与不同植物物种、光合作用速率和逆境发生的光谱行为的新视角。(C)2015 Elsevier Inc.保留所有权利。
The FLuorescence EXplorer (FLEX) satellite mission, candidate of ESA's 8th Earth Explorer program, is explicitly optimized for detecting the sun-induced fluorescence emitted by plants. It will allow consistent measurements around the O-2-B (687 nm) and O-2-A (760 nm) bands, related to the red and far-red fluorescence emission peaks respectively, the photochemical reflectance index, and the structural-chemical state variables of the canopy. The sun-induced fluorescence signal, overlapped to the surface reflected radiance, can be accurately retrieved by employing the powerful spectral fitting technique. In this framework, a set of fluorescence retrieval algorithms optimized for FLEX are proposed in this study. Two main retrieval approaches were investigated: i) the optimization of the spectral fitting for retrieving fluorescence at the oxygen absorption bands; ii) the extension of the spectral fitting to a broader spectral window to retrieve the full fluorescence spectrum in the range from 670 to 780 nm. The accuracy of the retrieval algorithms is assessed by employing atmosphere-surface radiative transfer simulations obtained by coupling SCOPE and MODTRAN5 codes. The simulated dataset considers more realistic conditions because it includes directional effects, and the top-of-atmosphere radiance spectra are resampled to the current specifications of the FLuORescence Imaging Spectrometer (FLORIS) planned to serve as the primary instrument aboard FLEX. The retrieval accuracy obtained at the O-2-A band is strongly affected by directional effects, and better performance is found in cases where directional effects are lower. However, the best performing algorithms tested provided similar performance, the RMSE (RRMSE) is 0.044 mW m(-2) sr(-1) nm(-1) (6.2%) at the O-2-A band, 0.018 mW m(-2) sr(-1) nm(-1) (2.9%) at the O-2-B band, and 6225 mW m(-2) sr(-1) (6.4%) for the spectrally integrated fluorescence emission. The promising results achieved open new perspectives extending fluorescence studies not only in limited absorption bands, but its spectral behavior in relation to different plant species, photosynthetic rates and stress occurrences. (C) 2015 Elsevier Inc. All rights reserved.