Harmonization of GEOV2 fAPAR time series through MODIS data for global drought monitoring.

The temporal consistency of the fAPAR GEOV2 full time series (constituted by data derived from SPOT-VGT1/2 and PROBA-V) is analyzed against the single-sensor MODIS dataset, with a particular focus on the most recent fAPAR anomalies (-scores) produced from PROBA-V in the period 2014-2017. The intercomparison highlights a systematic overestimation of GEOV2 fAPAR -scores when compared to MODIS fAPAR, likely related to the observed positive bias (over 90% of the domain) in the PROBA-V SPOT-VGT1/2 relationship. A simple two-step harmonization procedure has been proposed to remove this discrepancy, based on two separate linear corrections of SPOT-VGT1/2 (2001-2013) and PROBA-V (2014-2017) data with respect to MODIS, followed by a time lag correction.