Dryland hydroclimatic response to large tropical volcanic eruptions during the last millennium

Drylands are highly vulnerable to climate change due to their fragile ecosystems and limited ability to adapt. In contrast to the global drying after tropical volcanic eruptions shown previously, we utilize the last millennium simulations to demonstrate that large tropical volcanic eruptions can induce significant two-year hydroclimatic wetting over drylands. During this wetting period, which extends from the first to the third boreal winter after the eruption, several hydroclimatic indicators, such as self-calibrating Palmer Drought Severity Index based on the Penman-Monteith equation for potential evapotranspiration (scPDSIpm), standard precipitation evapotranspiration index (SPEI), aridity index (AI), top-10cm soil standard precipitation evapotranspiration index (SPEI), aridity index (AI), top-10cm soil drylands. The primary contribution to the wetting response is the potential evapotranspiration (PET) reduction resulting from dryland surface cooling and reduced solar radiation, as well as a weak contribution from increased precipitation. The latter is due to the wind convergence into drylands caused by slower tropical cooling. This dryland wetting response to volcanic eruptions is encouraging news for stratospheric sulfur aerosol injection, which mimics the cooling effect of volcanic eruptions for combating global warming.