How explosive volcanic eruptions reshape daily precipitation distributions

Abstract

Previous studies have found that global land precipitation is decreased after explosive volcanic eruptions, especially over global summer monsoon regions. However, detailed changes in daily precipitation distributions and related physical mechanisms remain unclear. This study examines responses of daily precipitation distribution to low-latitude volcanic eruptions using observations and Coupled Model Intercomparison Project Phase 6 (CMIP6) multi-model simulations. Observations reveal consistent decreases in daily precipitation intensity over global monsoon regions following the Pinatubo eruption across all percentiles, accompanied by decreases in frequency of moderate to heavy precipitation (above 70th percentile) and increases in light precipitation (10th to 40th percentiles). These observed changes are reasonably captured by CMIP6 multi-model simulations following Krakatau and Pinatubo eruptions, which induce strong precipitation reduction in both hemispheres. Detailed moisture budget analysis shows that reduced vertical moisture advection is a dominant process reshaping the daily precipitation distributions. It is further found that the weakened vertical moisture advection is contributed by both thermodynamic (atmospheric moisture decrease) and dynamic effects (suppressed vertical motion). Finally, CMIP6 models simulate robust El Niño occurrence in post-eruption years, which further enhances drying responses, explaining most of the precipitation decrease for 30th-60th percentiles, about a half for 70th-80th percentiles, and about one third for 90th-98th percentiles.