Standardised Precipitation Evapotranspiration Index
Multiscalar drought index based on climatic data
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The Standardized Precipitation Evapotranspiration Index (SPEI) is a multiscalar drought index based on climatic data. It was developed by Vicente-Serrano et al. (2010) at the Pyrenean Institute of Ecology in Zaragoza, Spain.[1] It can be used for determining the onset, duration and magnitude of drought conditions with respect to normal conditions in a variety of natural and managed systems such as crops, ecosystems, rivers, water resources, etc.[2][3][4]
The SPEI accounts not only for precipitation deficit but also for the role of the increased atmospheric evaporative demand on drought severity.[5] Evaporative demand is particularly dominant during periods of precipitation deficit. The SPEI calculation requires long-term and high-quality precipitation and atmospheric evaporative demand datasets. These can be obtained from ground stations or gridded data based on reanalysis as well as satellite and multi-source datasets.[5]
Datasets
Globally, the SPEIbase and Global Precipitation Climatology Centre (GPCC) drought index datasets are available at a relatively coarse spatial resolution. The SPEIbase is available at 0.5° resolution calculated from the Climatic Research Unit precipitation and potential evapotranspiration datasets. The GPCC drought index provides SPEI datasets at a 1.0° spatial resolution for limited timescales (1, 3, 6, 9, 12, 24, and 48 months).[5]
Inputs to SPEI datasets can include high-resolution potential evapotranspiration (PET) from the Global Land Evaporation Amsterdam Model (GLEAM) and hourly Potential Evapotranspiration (hPET). GLEAM is a set of algorithms designed to calculate actual evaporation, PET, evaporative stress, and root-zone soil moisture.[5]
Classification
| Value | classification |
|---|---|
| 2.0 or more | Extremely Wet |
| 1.5 to 1.99 | Very Wet |
| 1.0 to 1.49 | Moderate Wet |
| -0.99 to 0.99 | Normal |
| -1.0 to -1.49 | Moderate Dry |
| -1.5 to -1.99 | Very Dry |
| -2.0 or less | Extremely Dry |
See also
- Keetch–Byram drought index – Estimate of soil moisture deficit
- Palmer drought Index – Regional drought index
