## 2 Materials and Methods  
### Description of Datasets  
#### 2.1.1 Simulated Data  
The Soil Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model (version 1.53) by [PERSON] _et al._[33] was employed to simulate the training reflectance and SIF spectra. SCOPE is a vertical (1-D) integrated radiative transfer and energy balance model, which can simulate the canopy reflectance, photosynthesis, heat flux and chlorophyll fluorescence by linking the within-canopy radiative transfer with micro-meteorological processes. \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Parameter**} & \multicolumn{2}{c}{**Value**} & \multirow{2}{*}{**Unit**} & \multirow{2}{*}{**Description**} \\ \cline{2-2} \cline{4-5}  & & **Training** & & & \\ \hline Cab & 5, 20, 40, 60, 80 & 10, 30, 50, 70 & \(\mu\)g/cm\({}^{2}\) & Leaf chlorophyll a + b content \\ Cdm & 2, 10, 20 & 5, 15 & mg/cm\({}^{2}\) & Dry matter content \\ Cw & 5, 10, 20, 40 & 10, 30 & 10\({}^{-3}\)cm & Leaf water equivalent layer \\ Cs & 0 & 0 & fraction & Senescent material fraction \\ N & 1, 2 & 1.5, 2.5 & - & Leaf thickness parameters \\ LAI & 1, 2, 4, 6 & 1, 3, 5, 7 & m\({}^{2}\)/m\({}^{2}\) & Leaf area index \\ LIDFa & \(-\)0.35 & \(-\)0.35 & - & Leaf inclination \\ LIDFb & \(-\)0.15 & \(-\)0.15 & - & Variation in leaf inclination \\ FQE & 0.04 & 0.02, 0.04 & - & Fluorescence quantum yield efficiency \\ SZA & 20, 60 & 30, 40, 50 & degree & Solar zenith angle \\ VZA & 0, 30, 60 & 0, 20, 40 & degree & View zenith angle \\ RAA & 90 & 90 & degree & Relative azimuth angle \\ \hline \end{tabular}
\end{table} 
Table 1: Input leaf and canopy parameters used in the Soil Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model for the simulation of the training dataset. In order to make ensure that both the training and test datasets corresponded to the majority of the range of conditions encountered in practice, the parameter values for the training and test datasets were set to be different but not random (details listed in Table 1). The ranges of the main leaf and canopy parameters were set according to the statistics of the LOPEX'93 dataset [34] and empirical knowledge. As the fluorescence quantum yield efficiency (FQE) has no influence on the shape of fluorescence spectra, its value was set at a fixed 0.04 in the training dataset. Consequently, a total of 2880 samples were simulated for training and 2304 for testing. We combined the MODTRAN 5 [35] and SCOPE models to describe the interaction of the Top of Canopy (TOC) surface with the atmosphere and the incident irradiance from the sun and the sky, as described in Equations (1) and (2) [36]. \[E_{sun}=E_{s}^{o}\tau_{s}\cos\theta_{s} \tag{1}\]  
\[E_{sky}=\frac{E_{s}^{o}\cos\theta_{s}(\tau_{ud}+\tau_{su}\rho_{ud}\tau_{ud})}{ 1-\tau_{dd}\rho_{dd}} \tag{2}\]  
where \(E_{s}^{o}\) is the direct solar flux arriving at the top of atmosphere. \(\rho\) and \(\tau\) are the reflectance and transmittance of atmosphere, respectively, \(r\) is the surface reflectance, and the attached double subscripts refer to the associated incident and exiting flux types, where \(s\) stands for direct flux, and \(d\) for diffuse flux. \(\theta_{s}\) is the solar zenith angle. \(E_{s}^{o}\), \(\rho\) and \(\tau\) can be calculated by MODTRAN 5. As we did not take the influence of the atmospheric radiation transfer into account, the values of the atmospheric parameters were given fixed values (atmospheric profile: mid-latitude summer; aerosol model: rural; visibility: 23 km; surface height: 0 m). \(r\) can be simulated by the SCOPE model. In the MODTRAN 5 calculations, SRs of 0.3 nm, 0.5 nm, 1 nm and 3 nm were used, and the Spectral Sampling Intervals (SSIs) were set to be half of the SRs. Therefore, the downwelling irradiance and total upwelling radiance at the TOC can be calculated using Equations (3) and (4), respectively:  
\[E_{g}=E_{sun}+E_{sky} \tag{3}\]  
\[L=\frac{E_{g}}{\pi}\ R+SIF \tag{4}\]  
where \(R\) is the canopy reflectance. The SSI of SCOPE is 1 nm.