Asian Anthropogenic Aerosol Forcing Played a Key Role in the Multidecadal Increase in Australian Summer Monsoon Rainfall
Article
Fahrenbach, Nora L. S., Bollasina, Massimo A., Samset, BjØrn H., Cowan, Tim and Ekman, Annica M. L.. 2024. "Asian Anthropogenic Aerosol Forcing Played a Key Role in the Multidecadal Increase in Australian Summer Monsoon Rainfall." Journal of Climate. 37 (3), pp. 895-911. https://doi.org/10.1175/JCLI-D-23-0313.1
Article Title | Asian Anthropogenic Aerosol Forcing Played a Key Role in the Multidecadal Increase in Australian Summer Monsoon Rainfall |
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ERA Journal ID | 1978 |
Article Category | Article |
Authors | Fahrenbach, Nora L. S., Bollasina, Massimo A., Samset, BjØrn H., Cowan, Tim and Ekman, Annica M. L. |
Journal Title | Journal of Climate |
Journal Citation | 37 (3), pp. 895-911 |
Number of Pages | 17 |
Year | 2024 |
Publisher | American Meteorological Society |
Place of Publication | United States |
ISSN | 0894-8755 |
1520-0442 | |
Digital Object Identifier (DOI) | https://doi.org/10.1175/JCLI-D-23-0313.1 |
Web Address (URL) | https://journals.ametsoc.org/view/journals/clim/37/3/JCLI-D-23-0313.1.xml |
Abstract | Observations show a significant increase in Australian summer monsoon (AUSM) rainfall since the mid-twentieth century. Yet the drivers of this trend, including the role of anthropogenic aerosols, remain uncertain. We addressed this knowledge gap using historical simulations from a suite of Coupled Model Intercomparison Project phase 6 (CMIP6) models, the CESM2 Large Ensemble, and idealized single-forcing simulations from the Precipitation Driver Response Model Intercomparison Project (PDRMIP). Our results suggest that Asian anthropogenic aerosol emissions played a key role in the observed increase in AUSM rainfall from 1930 to 2014, alongside the influence of internal variability. Sulfate aerosol emissions over Asia led to regional surface cooling and strengthening of the climatological Siberian high over eastern China, which altered the meridional temperature and sea level pressure gradients across the Indian Ocean. This caused an intensification and southward shift of the Australian monsoonal westerlies (and the local Hadley cell) and resulted in a precipitation increase over northern Australia. Conversely, the influence of increased greenhouse gas concentrations on AUSM rainfall was minimal due to the compensation between thermodynamically induced wettening and transient eddy-induced drying trends. At a larger scale, aerosol and greenhouse gas forcing played a key role in the climate response over the Indo-Pacific sector and eastern equatorial Pacific, respectively (coined the “tropical Pacific east–west divide”). These findings contribute to an improved understanding of the drivers of the multidecadal trend in AUSM rainfall and highlight the need to reduce uncertainties in future projections under different aerosol emission trajectories, which is particularly important for northern Australia’s agriculture. |
Keywords | Aerosols/particulates; Atmospheric circulation; Australia; Monsoons; Precipitation; Anthropogenic effects/forcing |
Contains Sensitive Content | Does not contain sensitive content |
ANZSRC Field of Research 2020 | 370202. Climatology |
Byline Affiliations | University of Edinburgh, United Kingdom |
Institute for Atmospheric and Climate Science, Switzerland | |
Center for International Climate and Environmental Research, Norway | |
Centre for Applied Climate Sciences | |
Australian Bureau of Meteorology | |
Stockholm University, Sweden |
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