## 3 Results and Discussion
### Grasslands  
The comparisons between GlobAlbedo-derived (GA) and MODIS (MO) values for the grassland sites are shown in Figure 3. For the AU-Stp and US-AR2 sites the fAPAR values agree closely in terms of peak magnitude and timing albeit with the GA values lying slightly above the MO values during peak (summer) times. In the case of the AU-Stp site, the GA values show a longer delay before senescence in most years. This is also apparent in the RU-Upo site. Peak GA fAPAR values are lower than their MO counterparts for the CN-Du3 and RU-Upo sites. Agreement is reflected in the r\({}^{2}\) values, which range from 0.76 to 0.95. GA-derived values lie below the corresponding MO values for all sites bar US-Ar2 _i.e._, there is a positive slope between GA and MO values. The intercept between the two estimates of fAPAR is \(\leqslant\) 0.12 in all cases.  
Figure 3: _Cont._  
The LAI values lie between 1 and 2 for all sites bar RU-Upo, where peak values approach 4 in the summer. The timing of greenup agrees within 8-16 days between the two sets of products, and within 16 days for senescence. This suggests that estimates of canopy phenology properties will be consistent between the two datasets for this cover type. r\({}^{2}\) values between the two LAI datasets lie between 0.77 and 0.87 with the exception of CN-Du3, which has a larger slope of \(\sim\)2 and intercept of 1.3. This suggests there is a particular difference at this site, in terms of canopy structure between the datasets. Other than this there is a consistent positive slope _i.e._, as for fAPAR, MODIS LAI values are generally higher than the corresponding GA-derived values. The variation in uncertainty is apparent in both fAPAR and LAI, particularly at the RU-Upo and US-AR2 sites.  
The comparisons between GlobAlbedo-derived (GA) and MODIS (MO) values at the deciduous broadleaf forest sites are shown in Figure 4. There is a wider disagreement between the GA and MODIS fAPAR values in terms of peak values than for the grasslands sites, with the GA values consistently lower at the summer peak for all sites. Conversely, the GA values tend not to reach 0 in the winter, falling to 0.01-0.02, whereas the MO values tend to be lower and even 0 in some cases. In the case of the AU-Stp site, the GA values show a longer delay before senescence in most years. The timing of greenup and senescence agree within 8-16 days for all sites. The uncertainty in both datasets is also larger than for the grassland sites above, at both summer peak values, but also in winter. In the latter case this is likely to be due to clouds, snow and low sun angles, hence poor sampling and poor quality observations in general. r\({}^{2}\) values for fAPAR range from 0.86 to 0.92, with positive slope between 1.34 and 1.43 and intercept between 0.07 and 0.11.  
Figure 4: \(Cont\).  
Figure 3: 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.  
The LAI values in this case highlight the difference between the two datasets, with the MO values being substantially higher in all peak times, by a factor of two in some cases. The r\({}^{2}\) values lie between 0.84 and 0.90, with slope of around 2-2.3 in all cases, and with intercepts between \(-0.3\) and \(-0.2\).