Synergistic effect of land-atmosphere coupling and climate change on flash droughts

The land-atmosphere coupling is responsible for flash droughts as the reduced soil moisture increases sensible heat and consequently the lifting condensation level, which ultimately reduces convective precipitation. Meanwhile, the decrease in atmospheric humidity increases the evaporation demand, facilitates the drying of the land surface, and triggers flash droughts with rapid onset and devastating impact. However, whether the role of the land-atmosphere coupling is enhanced or weakened under climate change remains elusive, as previous studies are usually based on unconditional analysis without discriminating dry or wet extremes. Here, we start the investigation from a mega-flash drought occurred over the Yangtze River basin in southern China during the summer of 2022. Both the offline high-resolution land surface model simulations and the CMIP6 climate model data are used for the analysis. It is found that high temperature aggravates the 2022 flash drought onset speed and intensity, highlighting the importance of climate warming. Even under natural climate forcings, the land-atmosphere coupling increases the risks of flash drought intensity and onset speed. The synergy of coupling and anthropogenic climate change would further increase the risks. The synergistic effect on the long-term trends of flash droughts is also being explored, shedding light on the mechanism of flash droughts in a changing climate.