A Global Analysis of Future Compound Flood Drought Events

Dataset Description This dataset was produced as part of a research project aimed at quantifying historical and future occurrences of Compound Flood–Drought (CFD) events at the global scale. The analysis used simulations from the VIC-WUR hydrological model, which provides daily streamflow and soil moisture data for historical and future periods. The simulations cover two climate scenarios: SSP1-2.6 SSP3-7.0 These scenarios are forced by outputs from five Global Climate Models (GCMs) following the ISIMIP3b (Inter-Sectoral Impact Model Intercomparison Project phase 3b) protocol. Three types of compound flood–drought events are distinguished: Drought & Flood (D&F): simultaneous occurrence of drought and flood conditions Drought-to-Flood (DtoF): drought followed by a flood within a maximum lag of 6 months Flood-to-Drought (FtoD): flood followed by a drought within a maximum lag of 6 months Transitions between extremes are further classified based on the time lag between events: Slow transitions: > 90 days Rapid transitions: 30–90 days Abrupt transitions: < 30 days File Structure The dataset is organized into four main file categories: Flood–Drought files Frequency files Severity_abruptness files Seasonality files Each category contains three files: one for the historical period (1964–2014) one for SSP1-2.6 (2050-2100) one for SSP3-7.0 (2050-2100) 1. Flood–Drought Files These files contain daily occurrences of floods and droughts for all historical and future periods in each grid cell with mean yearly discharge > 100 m³/s. Variables thresh_soilmoist (historical file only)Monthly thresholds for soil moisture droughts in each grid cell. monthly_thresholds (historical file only)Monthly thresholds for hydrological droughts in each grid cell. flood_threshold (historical file only)Monthly thresholds for flood events in each grid cell. soil_droughtDaily indicator of soil moisture drought occurrence. 1 = drought 0 = no drought soilmoist_deficitDaily soil moisture deficit calculated as (soil moisture − threshold).Returns NA if no drought occurs on that day. dis_extremesDaily indicator of hydrological extremes. 0 = no extreme 1 = hydrological drought 2 = flood volume_deficitDaily flood volume or hydrological drought deficit.Returns NA if no flood or drought occurs. droughtDaily indicator of drought conditions (hydrological or soil moisture). 1 = drought 0 = no drought 2. Frequency files These files contain data on the frequency of compound flood–drought events in each grid cell with mean yearly discharge > 100 m³/s. Variables n_F&DNumber of Drought & Flood (D&F) events. n_DtoF_allDNumber of Drought-to-Flood events considering all drought types. n_FtoD_allDNumber of Flood-to-Drought events considering all drought types. n_DtoF_HDonlyNumber of Drought-to-Flood events considering hydrological droughts only. n_FtoD_HDonlyNumber of Flood-to-Drought events considering hydrological droughts only. n_DtoF_SMDonlyNumber of Drought-to-Flood events considering soil moisture droughts only. n_FtoD_SMDonlyNumber of Flood-to-Drought events considering soil moisture droughts only. 3. Severity and abruptness files These files contain data about the severity and abruptness of compound flood–drought events with mean yearly discharge > 100 m³/s. Variables transition_times_DtoF(FtoD)Transition time for each recorded CFD event, defined as the number of days between the end of the first extreme and the start of the second.Used for abruptness analysis. magnitude_flood_DtoF(FtoD/D&F)Flood magnitude for each recorded CFD event, stored per grid cell and per event type.Used for severity analysis. duration_DtoF(FtoD/D&F)Duration of the drought component for each CFD event.Used for severity analysis. This variable is also provided for each transition class: mod (slow transitions) rap (rapid transitions) abr (abrupt transitions) ECSI_sev_DtoF(FtoD/D&F)Empirical Compound Severity Index (ECSI) for each recorded CFD event, stored per grid cell and event type.Used for severity analysis. severities_(hydro/SM)droughts(floods)_DtoF(D&F/FtoD)Severity of hydrological or soil moisture droughts and floods for each CFD event.This variable was not used in the final analysis. ECWA_sev_DtoF(DtoF/FtoD)Empirical Compound Weighting Angle (ECWA) following Rezvani et al. (2023).This variable was not used in the final analysis. 4. Seasonality Files These files contain data on the seasonal characteristics of compound flood–drought events with mean yearly discharge > 100 m³/s. Variables date_drought(flood)DtoF(FtoD/D&F)(moderate/rapid/abrupt)Mean occurrence date (expressed as month of the year) of droughts or floods associated with moderate, rapid, or abrupt transitions in each grid cell. strength_seas_drought(flood)DtoF(FtoD/D&F)(moderate/rapid/abrupt)Strength of seasonality of droughts or floods associated with moderate, rapid, or abrupt transitions in each grid cell.