Precipitation-based indices are generally considered as the simplest indices because they are calculated solely based on long-term rainfall records that are often available.
The mostly used precipitation-based indices consist of
- Decile Index (DI)
- Hutchinson Drought Severity Index (HDSI)
- Percen of Normal Index (PNI)
- Z-Score Index (ZSI)
- China-Z Index (CZI)
- Modified China-Z Index (MCZI)
- Rainfall Anomaly Index (RAI)
- Effective Drought Index (EDI)
- Standardized Precipitation Index (SPI).