Drought indicators across Sweden (1975-2021)

This dataset collection is part of the research conducted for the study “Drought hazard assessment across Sweden’s diverse hydro-climatic regimes”. The R-scripts and datasets include values of the Soil Moisture Anomaly (SMA), as well as the Standardized Precipitation Index (SPI), Standardized Precipitation-Evapotranspiration Index (SPEI), Standardized Soil Moisture Index (SSMI), and Standardized Streamflow Index (SSI). SPI, SPEI, SSMI, and SSI were calculated at 1-, 3-, 6-, 12-, and 24-month timescales, while SMA is provided only at a monthly resolution. The data span the period from January 1, 1975 to December 31, 2021 and cover 39,635 Swedish sub-catchments. The R-scripts include the computational steps used to derive these indicators. All indicators were derived from simulated precipitation, evapotranspiration, soil moisture, and streamflow data produced by the S-HYPE hydrological model. Soil Moisture Anomaly (SMA) was computed through subtracting the mean of the daily average of soil moisture and dividing by the standard deviation. The monthly mean of the daily SMA values was then calculated. Using the monthly SMA values, 5 spatial clusters were identified as the optimal number of groups. Standardized drought indicators were calculated from daily precipitation, evapotranspiration, soil moisture, and streamflow simulations. Monthly values were calculated by summing precipitation and evapotranspiration, and averaging soil moisture and streamflow. SPI and SPEI were computed using the SPEI R package (Beguería and Vicente Serrano, 2023; Vicente-Serrano et al., 2010), with precipitation modeled by a Gamma distribution, following European standards (McKee et al., 1993). SPEI was based on the monthly difference between precipitation and evapotranspiration, modeled with a log-logistic distribution (Vicente-Serrano et al., 2010). SSMI and SSI were calculated using the SPEI package applying the log-logistic distribution. The HYPE model code, which was used in the Swedish national S-HYPE model setup, is available from the HYPEweb portal (https://hypeweb.smhi.se/model-water/; (SMHI, 2025a)). The meteorological data used for driving the S-HYPE model can be obtained upon contact with SMHI, and the hydrological data used are available from the Vattenwebb portal (https://vattenwebb.smhi.se/; (SMHI, 2025b)).