Spei Index

METEOROLOGY – CLIMATE INDICE & CLAIFICATION CALCULATOR Spei Index A precise tool.
📖
What is the Spei Index & How does it work?

The Standardised Precipitation-Evapotranspiration Index (SPEI) is a drought index that considers both precipitation and evapotranspiration to assess water balance conditions. It standardizes the difference between accumulated precipitation and potential evapotranspiration over a given time scale, allowing for comparisons across different climatic regions.

The SPEI is calculated by fitting the difference between cumulative precipitation and potential evapotranspiration to a probability distribution function (typically a Pearson Type III distribution) and then transforming this difference into a standardized normal variable using the inverse of the cumulative distribution function.

SPEI = Phi^{-1}left(frac{F(x)}{n+1}right)
var = meaning
⚙️
Parameters
Result —
❓
Frequently Asked Questions
What is the SPEI index used for?
The SPEI index is used to assess water balance conditions and monitor drought severity by considering both precipitation and potential evapotranspiration.
How does the SPEI index differ from other drought indices?
Unlike other indices, the SPEI considers both precipitation and evapotranspiration, providing a more comprehensive assessment of water balance conditions.
What time scales can be used for calculating the SPEI?
The SPEI can be calculated over various time scales, such as monthly, seasonally, or annually, allowing for flexibility in drought monitoring.
How is the SPEI standardized?
The SPEI standardizes the difference between accumulated precipitation and potential evapotranspiration by fitting it to a probability distribution, enabling comparisons across different climatic regions.
What does a higher SPEI value indicate?
A higher SPEI value indicates wetter conditions, while a lower value indicates drier conditions or drought.
Can the SPEI be used in any climate region?
Yes, the SPEI is designed to be applicable across different climatic regions due to its standardization process.
What software tools are commonly used for calculating the SPEI?
Commonly used software tools for calculating the SPEI include MATLAB, R (with specific packages like ‘spei’), and Python libraries such as ‘climdex.pcic’.

Results are for informational purposes only and do not constitute professional advice.