## 3 Results
### Intraseasonal SIF Variation and Anomalies for Different Vegetation Types  
The drought area was characterized by higher temperatures during the second half of both spring and summer season (Figure 3b). For the drought area, SIF-Diff was initially significantly negative at the start of the spring season for the agricultural area, whereas the difference was not significant for forests. Here, significance is considered as a departure of (SIF/fPAR/NDVI) values \(>\)1 standard error [31; 32], e.g., for Figure 3a, when the blue and red shades are not overlapping. However, with increase in Temp-Diff and VPD-Diff from a couple of weeks after the middle of spring season (Day of the year (DOY) - 120), SIF-Diff significantly increased across all land cover types (Figure 3a,b), with SIF-Diff values as high as 0.25, 0.65, 0.25, and 0.4 W/m\({}^{2}\)/sr/\(\upmu\)m for agricultural area, broadleaved, confierous, and mixed forests, respectively. The broadleaved forests (BLF) in the drought area occur across a large range of latitude (from 45 N in Germany to 70 N in Norway; Figure S2) and Koppen climate zones (warm summer and cool summer). More intense and early spring warming occurred in the warm summer climate, whereas a moderate and later warming occurred in the cool summer climate zone (blue and black line in Figure S7). This seems to have caused leaf flushing (represented by the blue and green box in Figure S7) at a difference of about 20 days between the two climate zones. Now, since our result is spatially and temporally aggregated, this shows two peaks during the spring for BLF. Thus, although there was no overall change in SIF for the spring season (Section 3.1), we observed a change in the intra-spring SIF variation pattern in 2018 compared to the mean, with an initial decrease (March to April) followed by a significant increase in SIF in May. This intra-spring SIF variation was reflected in the fPAR variations during the spring season for the drought area (Figure S4a). Thus, SIF variation \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Area**} & \multicolumn{2}{c}{**(a) Combined Spring-Summer**} & \multicolumn{2}{c}{**(b) Spring**} & \multicolumn{2}{c}{**(c) Summer**} \\ \cline{2-10}  & **SIF\_2018** & **SIF\_Mean** & **SIF-Diff** & **SIF\_2018** & **SIF\_Mean** & **SIF-Diff** & **SIF\_2018** & **SIF\_Mean** & **SIF-Diff** \\ \hline Europe & 0.642 & 0.670 & \(-\)0.028 & 0.523 & 0.534 & \(-\)0.011 & 0.766 & 0.820 & \(-\)0.054 \({}^{\ast}\) \\ Drought area & 0.558 & 0.596 & \(-\)0.038 & 0.407 & 0.388 & 0.019 & 0.711 & 0.814 & \(-\)0.103 \({}^{\ast}\) \\ Non-drought area & 0.684 & 0.660 & 0.024 & 0.601 & 0.560 & 0.041 & 0.766 & 0.767 & \(-\)0.001 \\ \hline \hline \end{tabular} \({}^{\ast}\)\(p\)-value \(<\) 0.001.  
\end{table} 
Table 1: European-wide mean SIF\_757 nm (W/m\({}^{2}\)/sr/\(\upmu\)m) values in spring, summer, and the combined spring-summer season and their corresponding anomaly (SIF-Diff) for whole of Europe, drought area and non-drought area. Figure 2: Overall solar-induced (chlorophyll) fluorescence (SIF) variation in (**a**) spring and (**b**) summer season for drought areas in 2018 (SIF\_2018, in orange) compared to mean SIF values from 2015–2017 (SIF\_Mean, in grey). Bars indicate the histogram of the SIF, whereas curves represent the density plot of the histogram. in spring was strongly related to fPAR for drought areas where continuously higher temperature and VPD were observed in the second half of the spring season (April-May). The summer season of 2018 was characterized by negative SIF-Diff (Figure 3), especially for agricultural areas which showed continuously negative values throughout the summer season (Figure 3). For forest areas, however, we observed significantly negative SIF-Diff only in the later part of summer (from July, DOY 185-215) when the temperature values were more than 5 degrees higher than the mean (Figure 3b).