Rethinking Hydroclimatic Extremes: Occurrence of abrupt Drought-to-Heavy-Precipitation transition events

Pallavi Goswami, Siqi Deng, Ailie J. E. Gallant, Ravikumar Guntu, Heidi Kreibich

Drought-to-heavy-precipitation abrupt transitions (sometimes called dry-to-wet extremes, whiplash events, or drought–flood transitions) are an emerging research focus. These are rapid shifts from a period of sustained drought (rainfall deficits, soil moisture stress, low streamflow) to intense precipitation or flooding over short timescales. Also described as climate whiplash events, they reflect the increasing volatility of the hydroclimate system. Unlike droughts, there’s no universally agreed metric for identifying drought-to-heavy precipitation abrupt transitions. In this study, we developed a precipitation-based dry-to-wet flip-flop event identification framework. The framework was applied to Australia and Europe to identify and study these events, along with answering the question: Are droughts and heavy precipitation mutually exclusive? Results showed that regions in mid-latitudes often have higher frequency and magnitude of these events, suggesting greater temporal variability in precipitation/weather processes in those regions. Further, these events are more likely to occur during austral summer and autumn (in Australia) and boreal spring (in Europe). While such flip-flops can have detrimental impacts through giving rise to flash flooding and blackwater events, they also facilitate seasonal recovery in meteorological drought conditions and hence are potentially important in meteorological drought breaking. There is a need to support adaptation initiatives to better protect human society from the losses caused by these events, as well as to move towards more compound event-resilient designing.