[2][3][4] The SPEI accounts not only for precipitation deficit but also for the role of the increased atmospheric evaporative demand on drought severity.
The SPEI calculation requires long-term and high-quality precipitation and atmospheric evaporative demand datasets.
These can be obtained from ground stations or gridded data based on reanalysis as well as satellite and multi-source datasets.
The SPEIbase is available at 0.5° resolution calculated from the Climatic Research Unit precipitation and potential evapotranspiration datasets.
The GPCC drought index provides SPEI datasets at a 1.0° spatial resolution for limited timescales (1, 3, 6, 9, 12, 24, and 48 months).