Lagged Compound Occurrence of Droughts and Pluvials Globally Over the Past Seven Decades

The drought-pluvial seesaw-defined as the phenomenon of pluvials (wet spells) following droughts (dry spells)-magnifies the impact of individual pluvial and drought events yet has not been systematically evaluated, especially at the global scale. We apply an event coincidence analysis to explore the aggregated seesaw behavior based on land surface model simulations for the past seven decades (1950-2016). We find that globally, about 5.9% and 7.6% of the land surface have experienced statistically significant (p<0.10) drought-pluvial seesaw behavior during the boreal spring-summer and fall-winter, with an average 11.1% and 11.4% of all droughts being followed by pluvials in the following season, respectively. Although this global frequency pattern is modest and coherent changes cannot be detected at the subcontinental scale, local hot spots of drought-pluvial seesaw have become more frequent than either droughts or pluvials alone in the last three decades, albeit with a small percentage of area coverage.