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Abstract:
Changes in global monsoon rainfall has a great influence on social and economic development. As an important factor of natural external forcing, it is of great scientific and social significance to understand the impact of volcanic eruptions on the hydroclimate over global monsoon regions. Here we show divergent monsoon responses to volcanic eruptions at different latitudes based on reconstructions, observations and climate model simulations. Monsoon precipitation decreased after tropical volcanic eruptions, which is caused by decreased moisture and weakened monsoon circulation. There is a distinct remote impact of volcanic forcing such that large volcanoes erupted at one hemisphere can enhance monsoon precipitation in the other hemisphere, resulting from enhanced cross equator flow. As an El Nino-like SST anomaly usually occurs after volcanic eruptions, it can further modulate the monsoon precipitation through atmospheric teleconnection. Bases on model simulations, we found that under ENSO neutral and warm phases initial conditions, the Pacific favors an El Niño-like anomaly after volcanic eruptions, while La Niña-like SST anomalies tend to occur following eruptions under ENSO cold phase initial condition, especially after southern eruptions. Such SST response further regulates the monsoon precipitation changes. The contribution of direct radiative forcing and indirect SST response to precipitation changes show regional differences. The direct radiative forcing dominates Northern hemispheric monsoon rainfall, while the Indirect SST response dominates Southern hemispheric monsoon rainfall. Our results imply that attention should be paid to the background oceanic state when predicting the global monsoon precipitation responses to volcanic eruptions.
