Palmer Drought Severity Index (PSDI) from LDEO/IRI Climate Data Library

The Palmer Drought Severity Index (PDSI) is devised by Palmer (1965) to represent the severity of dry and wet spells over the U.S. based on monthly temperature and precipitation data as well as the soil-water holding capacity at that location. These data consist of the monthly PDSI over global land areas from 1860-1995 derived using monthly surface air temperature (from Hansen and Lebedeff, 1987 and updates) and precipitation (from Dai et al., 1997) data. Soil-holding capacity was fixed to climatological maps from Webb et al. (1993). More details can be found in Dai, et al. (1998).