ADO Factsheet: Standardized Precipitation Index (SPI)

The Standardised Precipitation Index (SPI) is the most commonly used index worldwide for detecting and characterising meteorological droughts. A meteorological drought is defined as a period with abnormal precipitation deficit, in relation to normal conditions for a region, represented as a long-term average. The SPI shows the normalisedanomalies (deviations from the long-term average) of the observed total precipitation for any given location and accumulation period of interest. The name of the index is usually modified to include the accumulation period. SPI-3, for example, refers to accumulation period of three months (JRC EDO, 2020).

标准化降水指数（Standardised Precipitation Index，SPI）是全球范围内最常用于检测与表征气象干旱的指标。气象干旱被定义为某一时期内降水相较于区域长期平均正常水平出现异常短缺的状态。SPI可针对任意给定地点与关注的累积时段，计算实测总降水量的归一化异常值（即与长期平均值的偏差）。该指数的名称通常会补充标注其累积时长参数，例如SPI-3即代表累积时长为3个月（JRC EDO，2020）。