- Percent of normal precipitation
Ratio of actual to normal precipitation for a given location
and a given period, expressed as a percentage.
- Palmer drought severity index
Index based
on the supply-and-demand concept of the water-balance equation, taking into account
the precipitation deficit.
- Reclamation drought index
Tool for defining drought severity and duration, and for predicting the beginning
and end of a drought period. It incorporates the supply components of
precipitation, snowpack, streamflow, and reservoir levels.
- Intensity-duration-frequency
The climate types are defined across the climatic spectrum in terms of the ratio of mean annual precipitation
to annual global terrestrial precipitation. Drought intensity is related to duration and frequency across the climatic spectrum.