## 3 Results and Discussion
### Evergreen Needleleaf Forest
The African site, ML-Kem, shows a different phenology between the two datasets, with a much more gradual senescence in the MO values than in the GA values. Again, this may be a result of the explicit consideration of understory vegetation in the MODIS values, which is typically strongly dependent on seasonal rainfall. The otherwise close agreement in timing and peak values is demonstrated by the \(r^{2}\) values of 0.81-0.95, with much lower slope (0.97-1.42) than for the forest sites above and intercepts in the range \(-\)0.2-0.1. LAI values agree to within 10%-15% in peak season for CA-MA2 for example. Agreement on timing is also strong for CA-MA2 and US-Wi6, as demonstrated by \(r^{2}\) values > 0.9, but lower for EE-Aar and ML-Kem (\(r^{2}\) values 0.68 and 0.71 respectively). Slope in these sites lies between 1.06 and 1.32 (again, the ML-Kem site is the higher one) and intercepts are \(-\)0.41-0.15. Figure 6: Top row: GlobAlbedo-derived and MODIS fAPAR values for 2002–2011; second row: scatter plot of fAPAR values; third row: GlobAlbedo-derived and MODIS LAI values for 2002–2011; fourth row: scatter plot of LAI values. Error bars for GlobAlbedo values represent the uncertainty of parameter retrieval, and for the MODIS data, the variance of the \(3\times 3\) pixel window centered on the comparison site. Figure 7: _Cont._  
Miscellaneous  
The comparisons between GlobAlbedo-derived (GA) and MODIS (MO) values at the miscellaneous sites are shown in Figure 8. The fAPAR values in the European sites (unsurprisingly) follow very similar patterns to the evergreen needleleaf and mixed forest sites above, with close timing (r\({}^{2}\)\(\sim\) 0.6), but very different peak values between GA and MO values. Both these sites experience significant and extended snow cover during the winter, which will affect retrieval values and timing during spring particularly. In addition, both sites have significant understory which may have a different phenology to the overstory forest canopy. Mixed phenology of this sort is always likely to introduce uncertainty in retrieved timing information. This is also likely to affect the MODIS and GlobAlbedo-derived parameter retrievals slightly differently due to the different assumptions underlying the retrieval methods. In the two tropical sites fAPAR values are particularly variable, for both the GA and MO data, and with a much less obvious (or clear) seasonality (r\({}^{2}\)\(\sim\) 0.1). This is likely to be due to both cloud, and the inherently different seasonality in these tropical regions, dominated by evergreen broadleaf trees and rainfall seasonality. The uncertainty in the MODIS values is testament to this variability. The LAI values are very different between GA and MO across all sites, but with almost no correlation in the tropical sites. This is reflected in r\({}^{2}\) values close to 0. This would indicate that the derived values should be interpreted with care in terms of timing and magnitude (relative or otherwise) at sites of this sort. Figure 8: _Cont._  
Figure 4:0 Top row: GlobAlbedo-derived and MODIS fAPAR values for 2002–2011; second row: scatter plot of fAPAR values; third row: GlobAlbedo-derived and MODIS LAI values for 2002–2011; fourth row: scatter plot of LAI values. Error bars for GlobAlbedo values represent the uncertainty of parameter retrieval, and for the MODIS data, the variance of the 3 \(\times\) 3 pixel window centered on the comparison site. Summary of Site Comparisons  
A summary of the results for the various sites is presented in Table 2 below, comprising the upper and lower values of the slope and intercept of the linear regression between the GlobAlbedo-derived and MODIS values of fAPAR and LAI.