Abstract
Asian summer monsoon (ASM) precipitation is the primary water resource for agriculture in many Asian countries that have experienced rapid economic growth in recent decades, thus implying the necessity for further investigations on both the internal variability of the ASM and the influence of external factors on the ASM. Using long-term high-resolution (0.5° × 0.5°) observed precipitation data, contrary to previous studies on inter-annual timescale, we showed that over the last 110 years, volcanic eruptions have influenced ASM variations on an inter-decadal timescale via teleconnections with the Atlantic Multi-decadal Oscillation (AMO). This relationship was also confirmed by Coupled Model Intercomparison Program Phase 5 (CMIP5) model simulations. During the active volcanic eruption periods (1901–1935 and 1963–1993), significantly lower ASM precipitation was observed compared with that during the inactive volcanic eruption period (1936–1962). We found that during active volcanic eruption periods, which correspond to a negative AMO state, there is an anomalously weakened Walker circulation over the tropical Pacific that transports less moisture to the ASM region and subsequently reduces ASM precipitation. This new finding may help improve decadal predictions of future changes in the ASM.
Highlights
The demand for decadal climate predictions is currently increasing, which is necessary for infrastructure planning, energy policies, economic development, and societal sustainability[1]
Over the Asian monsoon region, large volcanic eruptions correspond to a weakening of the East Asian Summer Monsoon (EASM) circulation and subsequent reductions in EASM rainfall[14,15,16,17] the impacts are relatively short lived[11]
On the aspect of long-term influence, both proxy records[18] and model simulations[19] suggest that volcanic eruptions have played a dominant role in pacing the Atlantic Multi-decadal Oscillation (AMO), which has a potential influence on the EASM3,20, since the end of the Little Ice Age
Summary
Asian Summer Monsoon over the last 110 years received: 14 June 2016 accepted: 13 January 2017 Published: 16 February 2017. Using long-term high-resolution (0.5° × 0.5°) observed precipitation data, contrary to previous studies on inter-annual timescale, we showed that over the last 110 years, volcanic eruptions have influenced ASM variations on an inter-decadal timescale via teleconnections with the Atlantic Multi-decadal Oscillation (AMO) This relationship was confirmed by Coupled Model Intercomparison Program Phase 5 (CMIP5) model simulations. Inter-decadal variability can explain the different trends over the period since the 1950s4,5 and the period since the 1980s6 To confirm that this inter-decadal variability was induced by the volcanic eruptions, a total of four simulations were run using the Community Earth System Model version 1 with Community Atmospheric Model version 5 (CESM1-CAM5) from the Coupled Model Intercomparison Program Phase 5 (CMIP5) to differentiate the influences from anthropogenic forcing (i.e., anthropogenic greenhouse gas, anthropogenic aerosol, and land use and cover change), solar radiation forcing, and volcanic forcing. This finding indicated that the timing and magnitude of the internal influence on the AMO from the AMOC can be changed by external forcing[23,24]
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