Fig. 1: Historical characteristics of compound drought events.

a Map showing the ten SREX regions (red line) and the ocean regions (blue dashed lines) used to define various modes of variability considered in this study. Red text indicates the fraction of each SREX region with high entropy values [entropy > 4.86, which is the median entropy value across ten SREX regions] (teal color). b Historical timeseries of the number of regions experiencing summer season (June–September) drought (gray) and the total drought affected area (green) based on the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) precipitation data (1981–2018). The gray dashed line indicates the threshold of the number of regions used to define a compound drought event. Gray shading indicates the years with compound droughts. c Drought affected area in each season over each SREX region. Blue circles indicate seasons when the drought-affected area exceeds 80^th percentile of the long-term average drought area. The magnitude of the 80^th percentile thresholds for drought area are indicated on the right beside each region.