Fig. 6: Influence of modes of variability on compound drought characteristics.

The distribution of a number of regions under drought, b drought area, and c drought intensity during seasons with individually occurring variability modes and co-occurring conditions noted below each boxplot, from the CESM preindustrial simulation. Horizontal gray solid lines indicate the thresholds used to define a compound (i.e., \(\ge\) three regions under drought, gray line), b widespread (i.e., events with >90^th percentile of total area (~21%) across all ten regions concurrently affected by drought, gray line), and c severe (i.e., average SPI across all drought affected areas < 10^th percentile (~−1.52), gray line) droughts. Text above the boxplots in a indicates the probability of compound droughts under each condition, b indicates the probability of experiencing widespread droughts and c indicates the probability of experiencing intense droughts. For example, the probability of three or more regions concurrently affected by droughts under neutral and Niño3.4⁺ conditions is 0.1 and 0.41, respectively. Gray arrows indicate significant differences in the distribution of drought area and intensity corresponding to various conditions relative to neutral conditions at 5% significance level. Green arrows indicate significant differences in the distributions between the co-occurring conditions and Niño3.4⁺ conditions at 5% significance level. Black dots show the mean of the distribution in each boxplot.