While SPI data from corrected real-time satellite data are
consistent with GPCP data, one can see discrepancies over
several regions. For example, all data sets correctly identify
the 2010 drought of Horn of Africa (see figure 4). Also, the
2010 drought of Australia has been captured in all data sets
(see figures 3 and 4). However, discrepancies between SPI
values form reference GPCP and corrected satellite data can
be observed over several regions (e.g., China). Overall, the
SPI data derived from the merged GPCP-PERSIANN is in
a better agreement with GPCP data for the validation period
(2010). For example, the 2010 Amazon drought (Lewis et al
2011, Marengo et al 2011) has been correctly identified in the
merged GPCP-PERSIANN, while it does not appear in the
merged TRMM-RT and GPCP (see figure 3 left panels).