Mount Pinatubo's effect on the moisture-based drivers of plant productivity

Abstract. Large volcanic eruptions can significantly influence the climate system by altering the stratospheric sulfate concentrations, atmospheric radiative balance, stratospheric and surface temperature, and regional hydroclimate. A comprehensive understanding of the volcanically-driven regional hydroclimate response is essential for assessing the socio-economic implications of such short-term episodic climate perturbations, which can lead to droughts, with potential significant impacts to vulnerable civilizations that depend on flooding as a natural crops irrigation mechanism. However, the regional rainfall response to volcanic forcings is substantially dominated by the natural variability in the rainfall response, and which creates a gap in our understanding of how eruptions affect ecohydrological conditions and plant productivity. Here, we explore the understudied store (soil moisture) and flux (evapotranspiration) of water as the short-term ecohydrological control over plant productivity in response to the 1991 eruption of Mt. Pinatubo. We used the NASA's Earth system model for modeling of the Mt. Pinatubo eruption and detect the ensuing hydroclimate responses. The model simulates a mean surface cooling of ∼ 0.5 °C following the Mt. Pinatubo eruption. The rainfall response is spatially heterogeneous with large temporal variability, yet still shows suppressed rainfall in the northern hemisphere after the eruption. We find that up to 10 %–15 % of land regions show a statistically significant hydroclimate response (wet and dry) as calculated by the Soil Moisture Deficit Index (SMDI) and Evapotranspiration Deficit Index (ETDI). Results confirm that these impact metrics successfully present a more robust understanding of plant productivity. Our results also explain the geographical dependence of various contributing factors to the compound response and their implications for exploring the climate impacts of such episodic forcings.