Future Projections of Global Drought and Pluvial Event Characteristics

An over or under abundance of precipitation impacts can have significant impacts across a variety of sectors including agriculture and water resource management. To adequately prepare for drought and pluvial events in the future, it is important to understand historical and future trends and variability in the characteristics of these events. Prior work has focused extensively on the characteristics of drought events but little work has been undertaken on pluvial events despite evidence that precipitation may become more variable in the future. Hence, this study examines the spatial and temporal characteristics of global drought and pluvial events including intensity, duration, and frequency in the past and future. Drought and pluvial events are defined using the Standardized Precipitation Index (SPI), a measure based solely on precipitation, and therefore is concerned with meteorological drought/pluvial events at multiple severity thresholds. This study uses a variety of precipitation observations and 24 global climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to systematically evaluate historical drought and pluvial characteristics as well as investigate future projections using the Representative Concentration Pathway 8.5 experiment. Results show increased variability in SPI in the future across the globe, which is accompanied by drought and pluvial events becoming more intense. Changes in drought and pluvial event frequency are more spatially variable but larger than changes in the duration of events. It is also apparent that drought and pluvial characteristics are increasing, especially intensity, in regions with wetting and drying trends respectively. This suggests that in some regions where precipitation is projected to increase in the future, drought events will still become more intense and longer lasting (and vice versa for pluvial events). This study diagnoses characteristics of drought and pluvial events in observations and historical and future CMIP5 simulations, revealing contrasts and similarities between projections of drought and pluvial events across the globe as a basis for additional regional evaluations.