Table 1 - uploaded by Yves Goulas
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Current techniques for large scale remote sensing of fluorescence aim at quantifying the sun-induced fluorescence (SIF) in absorption features present in the incoming radiation. However, these techniques allow measurement of the emitted fluorescence flux but do not provide a direct assessment of the fluorescence yield, which is the true variable li...
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... later parameter depends on spot size at ground level and aircraft speed. Fig. 9 gives MPE as a function of illuminated spot diameter at ground level, compared to the exposure (1.5 mJ m -2 ) induced by the fluorescence lidar with specifications given in Table 1. It shows that eye safety is achievable under good operational conditions. ...
Citations
... Therefore, this model provides the missing link between fluorescence spectra measured at TOC and leaf fluorescence -which is the most known and studied level-and quantifies fluorescence re-absorption in the canopy, a phenomenon that has been mentioned but never quantified in literature. Moreover, this model could retrieve fluorescence spectra at leaf or chloroplast level from a large scale plant cover, when measuring fluorescence at middle scales with active sensing techniques (Andersen et al., 2006;Goulas et al., 2014), thus overcoming leaf to leaf heterogeneity, which is a problem when trying to diagnose several plants (Cendrero-Mateo et al., 2016). Furthermore, as it is possible to retrieve the spectral distribution of fluorescence of chloroplasts from that at leaf level by measuring leaf reflectance (Ramos and Lagorio, 2004), we were able to predict the shape of chloroplast spectrum, starting from that of the canopy. ...
Chlorophyll fluorescence is widely used as an indicator of photosynthesis and physiological state of plants. Remote acquisition of fluorescence allows the diagnosis of large field extensions, even from satellite measurements. Nevertheless, fluorescence emerging from chloroplasts, the one directly connected to plant physiology, undergoes re-absorption processes both within the leaf and the canopy. Therefore, corrections of the observed canopy fluorescence, taking into account these two re-absorption processes may help to draw accurate inferences about plant health. Here, we show the theoretical development and experimental validation of a model that allows to retrieve the spectral distribution of the leaf fluorescence spectrum from that on top of canopy (TOC) using a correction factor which is a function of both canopy and soil reflectance, and canopy transmittance. Canopy fluorescence spectra corrected by our theoretical approach and normalized shows 95% correlation with the normalized fluorescence spectrum at leaf-level, thus validating the model. Therefore, our results provide a physical explanation and quantification for fluorescence re-absorption within the canopy, a phenomenon which has only been mentioned but never measured up to the date. From a more general perspective, this new analytical tool together with the one previously developed by Ramos and Lagorio (2004) allows to obtain the spectral distribution of chloroplast fluorescence spectrum from that on top of canopy (TOC).
