## 3 Results and Discussion
### Whole-Hemisphere Comparisons  
Comparisons are shown between the GlobAlbedo-derived (GA) and MODIS (MO) fAPAR and LAI values, on a hemisphere and seasonal basis, for 2005 and 2011 (towards the start and end of the GA record) in Figure 13 (fAPAR) and Figure 14 (LAI). All valid land tiles lying in horizontal rows 0-8 on the MODIS tile map are considered as Northern Hemisphere (NH, 161 tiles); all valid land tiles lying in horizontal rows \(>\)8 are considered Southern Hemisphere (SH, 113 tiles). Data from DOY 185 (NH) and DOY 361 (SH) are considered \"summer\"; data from DOY 001 (NH) and DOY 185 (SH) are considered \"winter\". Each tile in each summer/winter case, for each year, is compared by calculating a linear regression between the GA-derived and MO values, for all valid land pixels. The resulting differences between the two are characterized by the slope and intercept of the regression in each case, and the RMSE of the linear model fit, weighted by the number of valid pixels in each tile. These values are collected and shown in (normalised) histograms below. These histograms indicate the consistency (or otherwise) of the agreement between the GA-derived and MO values from season to season and  
Figure 12: Regional comparison of GlobAlbedo-derived (GA) and MODIS (MO) fAPAR and LAI. (**Top row**): GA fAPAR (**left panel**) and LAI (**right panel**); (**middle row**): MO fAPAR (**left panel**) and LAI (**right panel**); (**bottom row**): heatmap scatter plot between the GA (x-axis) and MO (y-axis) values, DOY 001 for all years 2002–2011: fAPAR (**left panel**) and LAI (**right panel**). from year to year. They also summarize the overall magnitude of slope and intercept between the GA-derived and MO values. Figure 14: Comparison of whole hemisphere GlobAlbedo-derived (GA) and MODIS (MO) LAI. Each panel shows a histogram of NH and SH correlation coefficient (\(\mathbf{r}^{2}\)), slope and intercept, for regression of GA v MO. (**Top row**), 2005: **(left panel)**: day-of-year (DOY) 001; (**right panel**): DOY 185. (**Bottom row**), 2011: **(left panel)**: DOY 001; (**right panel**): DOY 185. Figure 13: Comparison of whole hemisphere Glob Albedo-derived (GA) and MODIS (MO) fAPAR. Each panel shows a histogram of NH and SH histograms of correlation coefficient (\(\mathbf{r}^{2}\)), slope and intercept, for regression of GA v MO. (**Top row**), 2005: **(left panel)**: day-of-year (DOY) 001; (**right panel**): DOY 185. (**Bottom row**), 2011: **(left panel)**: DOY 001; (**right panel**): DOY 185. Figure 13 demonstrates correlation between the fAPAR products is almost exclusively positive with r\({}^{2}\) values exceeding 0.8 for: 37% of NH tiles and 52% of SH tiles on 2005 DOY 001 (NH winter, SH summer). This fraction rises in 2005 for DOY 185 to 48% and 63% of the NH and SH tiles respectively. For 2011, the distribution of r\({}^{2}\) values is almost identical. The slope and intercept of the correlation between the two products obviously represent the translation from one to the other. If the two datasets are to be compared or used in conjunction with each other, then these values could be used for transforming from one to the other. From Figure 13 the gradient between the fAPAR products lies between 0.5 and 1.5 for \(\sim\)70% of all tiles on DOY 001, and 80% of all tiles on DOY 185 for both 2005 and 2011. Lastly, the intercept of the linear regression of the fAPAR products lies within \(-\)0.1 and 0.1 for 90%-95% of all tiles in both 2005 and 2011, with a slightly greater spread of values for winter cases than summer. The correlation between LAI estimates summarized in Figure 14 is slightly weaker than for fAPAR, with r\({}^{2}\) exceeding 0.8 for 13% (NH) and 20% (SH) of tiles for 2005 DOY 001, and 15% (NH) and 34% (SH) of tiles for 2005 DOY 185. The values for 2011 are very similar. This indicates that the correlation is stronger in general for the SH tiles. The gradient of the correlation between the LAI products lies between 0.5 and 1.5 for 42% (NH) and 24% (SH) of cases in 2005 DOY 001.