PDSI: University of Idaho Palmer Drought Severity Index (IDAHO_EPSCOR/PDSI)

The Palmer Drought Severity Index dataset provides
high spatial resolution (~4-km) thrice-monthly estimates of this
widely used measure of integrated water supply and demand anomalies
across the contiguous United States from 1979-present. The PDSI
is calculated using precipitation and potential evapotranspiration
derived from the gridded meteorological dataset of Abatzoglou (2013).

Potential evapotranspiration is computed using the Penman-Montieth
equation for a reference grass surface. Available soil water holding
capacity in the top 2.5m of the soil was derived from the STATSGO
soils database and used in the computations. Whereas PDSI has typically
been computed on monthly timescales, we compute these data three-times
a month to provide more timely updates. Due to the spin-up of PDSI
calculations, data for the first year of record should be used
sparingly.

This dataset contains provisional products that are replaced with
updated versions when the complete source data become available.
Products can be distinguished by the value of the ‘status’ property.
At first, assets are ingested with status=‘early’. After several
days, they are replaced by assets with status=‘provisional’.
After about 2 months, they are replaced by the final assets with
status=‘permanent’.