Standardized Precipitation Index (SPI)

"The Standardized Precipitation Index (SPI) is a widely used index to characterize meteorological drought on a range of timescales. On short timescales, the SPI is closely related to soil moisture, while at longer timescales, the SPI can be related to groundwater and reservoir storage. The SPI can be compared across regions with markedly different climates. It quantifies observed precipitation as a standardized departure from a selected probability distribution function that models the raw precipitation data. [...]

SPI = (P - P*) / σp

where P = precipitation

p* = mean precipitation

σp = standard deviation of precipitation" (Keyantash, John & National Center for Atmospheric Research Staff, 2018)

Sources

"The Climate Data Guide: Standardized Precipitation Index (SPI)". Keyantash, John & National Center for Atmospheric Research Staff (Eds). Last modified 07 Aug 2018. https://climatedataguide.ucar.edu/climate-data/standardized-precipitati….
Accessed Mar 1, 2019.

Related Content

Article

Real-time drought monitoring from Climate Hazards group Infrared Precipitation with Stations (CHIRPS)

Different parts of world are experiencing extreme hydrological hazards such as droughts, flooding and other related events. Droughts are associated with absence of rainfall occurrence over an extended period. According to the United Nations (2022), the frequency and intensity of drought events in the last two decades has increased by 29%. These figures are expected to increase further in the coming years due to climate change (Gunathilake et al., 2020).