PNNL

Abstract

Flash droughts have become a growing concern, as they can emerge rapidly and increase the risk of crop failure. Although past studies have investigated the meteorological drivers of flash drought, the processes distinguishing flash drought from traditional drought and their differential responses to a warming climate remain largely unexplored. This study delves further into the mechanism by which vegetation regulates flash drought and its future change. Large ensemble simulations show robust increases in flash drought over the northern mid-to-high latitudes (e.g., 67% and 46% increases in Eastern U.S. and North Asia in 2050-2100 relative to 1950-2000), where the growing season is lengthening. Although greening might suggest reduced drought stress, it drives precipitation-soil moisture-evapotranspiration decoupling by increasing evapotranspiration partitioning to transpiration. The latter weakens the constraints of concurrent precipitation on evapotranspiration, thus accelerating soil moisture depletion under high evaporative demand, driving a slow-to-rapid drought transition in the future.