Standardised Precipitation-Evapotranspiration Index - ERA5_QM SPEI-1

The Standardized Precipitation-Evapotranspiration Index (SPEI) represents a standardized measure of what a certain value of surface water balance (precipitation minus potential evapotranspiration) over the selected time period means in relation to expected value of surface water balance for this period. SPEI is calculated on different time scales (1, 2, 3, 6, 12 months). The value of the SPEI index around 0 represents the normal expected conditions for the surface water balance in the selected period based on the long-term average (1981-2020). The value of 1 represents approximately one standard deviation of the surplus in the surface water balance, while the value of -1 is about one standard deviation of the deficit. Drought is usually defined as period when SPEI values fall below -1. Input precipitation data is downscaled from ERA5 reanalysis using quantile mapping. Contains modified Copernicus Climate Change Service information [1978-current year]; Contains modified Copernicus Atmosphere Monitoring Service information [1978-current year]. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.

标准化降水蒸散指数（Standardized Precipitation-Evapotranspiration Index，SPEI）是一类标准化度量指标，用于量化特定时段内地表水平衡（降水量减去潜在蒸散量）的实际值与该时段地表水平衡长期预期值之间的相对偏离程度。SPEI可基于1、2、3、6、12个月等不同时间尺度开展计算。基于1981-2020年的长期气候平均值，当SPEI指数约为0时，代表所选时段的地表水平衡处于正常预期状态；SPEI值为1时，大致对应地表水平衡盈余1个标准差，而值为-1时则对应地表水平衡亏缺1个标准差。通常将SPEI值低于-1的时段定义为干旱事件发生时段。本数据集所用的输入降水数据基于ERA5再分析资料，通过分位数映射法完成降尺度处理。本数据集包含经修改的哥白尼气候变化服务（Copernicus Climate Change Service）信息[1978-当年]；同时包含经修改的哥白尼大气监测服务（Copernicus Atmosphere Monitoring Service）信息[1978-当年]。欧洲委员会及欧洲中期天气预报中心（ECMWF）均不对任何因使用本数据集所含哥白尼相关信息或数据所引发的后果承担责任。