The Effect of Volcanic Eruptions on the Life Cycle of the Indian Summer Monsoon

Abstract

Large volcanic eruptions are a source of climate variability, affecting global temperatures and precipitation. The hydrology of the Indian monsoon region is particularly sensitive to volcanic forcing. Previous studies have focused on the seasonal mean response of the Indian summer monsoon to eruptions. Here, we investigate changes in the onset and withdrawal of the monsoon, which are important characteristics that affect the water budget of the region. Using large ensemble simulations in the Max Planck Institute Earth System Model, with idealised eruptions that inject 40 Tg of sulphur into the stratosphere at varying latitudes, we find changes in the monsoon onset and withdrawal dates by a few weeks compared to an unforced case. We explain the changes in onset dates within the low-level jet and ITCZ frameworks, which have been used to explain the internal variability of the monsoon onset. We find that the length of the Indian summer monsoon is strongly dependent on the eruption latitude. Our results show a shorter (longer) Indian monsoon duration, as opposed to weakened (strengthened) monsoon circulation, drives changes in the total seasonal precipitation following a Northern (Southern) Hemispheric eruption.