*2.9. Model Validation*

Pixel errors (*E*) for all broad bands and for both intrinsic albedos were calculated as the difference between the predicted and MCD43A albedo retrievals (both at the local solar noon):

$$E\_{p,m} = \mathbb{Z}\_{p,m} - a\_{p,m} \tag{6}$$

where *<sup>α</sup>p*,*<sup>m</sup>* is the predicted and *<sup>α</sup>p*,*<sup>m</sup>* is the MCD43A albedo retrieval for month *m* and pixel *p*. Because our main interest was to assess the prediction performance of the individual endmember (land cover type) models, we limited the validation sample to a subset of pixels containing homogeneous land cover—defined here as those whose total area contained ≥95% of a single endmember type.
