The influence of the Asian summer monsoon on volcanic aerosol transport in the UTLS region

The atmospheric background conditions, the amount of emitted sulfur dioxide, and the plume heights of volcanic eruptions are all essential parameters that directly determine the transport pathways of volcanic aerosols and the potential climate impact. This study analyses the influence of the Asian summer monsoon on volcanic aerosol transport. By enhancing the meridional transport in the UTLS region and lifting volcanic aerosols across the tropopause, the ASMA significantly expanded the potential effects of volcanic eruptions.
The influence of the Asian summer monsoon on volcanic aerosol transport in the UTLS region
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The regional and global climate impacts of volcanic aerosols in the upper troposphere/lower stratosphere (UTLS) have received great attention. The aerosols transported to the UTLS region potentially reduce average global surface temperatures and alter atmospheric circulation. Although large volcanic eruptions have been rare in recent decades, small and medium volcanic eruptions have continuously increased stratospheric aerosol levels. The sulfate aerosol from volcanism has become a significant source of aerosols in the UTLS region.

The Asian summer monsoon (ASM) is a significant system in the Northern Hemisphere. Studying its influence on the transport and exchange of volcanic aerosols is of great significance for exploring the distribution of volcanic aerosols and their potential climate effects.

Erupting Nabro Volcano. The figure was acquired by the Advanced Land Imager (ALI) aboard the Earth Observing-1 (EO-1) satellite on June 24, 2011, and distributed by NASA Earth Observatory.

Dr. Xue Wu and her colleagues from the Institute of Atmospheric Physics, CAS, collaborated with Dr. Lars Hoffmann and Dr. Sabine Griessbach of Forschungszentrum Jülich,  retrieved realistic, altitude-resolved SO2 emissions of a middle-latitude volcanic eruption (Sarychev 2009) and a tropical volcanic eruption (Nabro 2011) and initialized the simulations of the long-range transport and dispersion of the sulfate aerosol plumes with the retrievals, to study the influence of the ASM system on the long-range aerosol transport.

The aerosol transport of the Sarychev eruption (2009) under the influence of the Asian summer monsoon anticyclone (ASMA). Thick black contours mark the boundary of the ASMA. The filled red triangles indicate the Sarychev volcano.

The aerosol transport of the Nabro eruption (2011) under the influence of the Asian summer monsoon anticyclone (ASMA). Thick black contours mark the boundary of the ASMA. The filled red triangles indicate the Nabro volcano.

Comparing the transport of the aerosols produced by the Sarychev eruption in 2009 and the Nabro eruption in 2011 under the influence of the ASM, they found that the ASM can enhance the quasi-horizontal meridional transport between the middle latitudes and the tropics. Furthermore, the horizontal barrier effect of the ASM anticyclone (ASMA) caused a significant aerosol gradient inside and outside the ASMA. In addition, driven by diabatic heating in the ASMA region, the volcanic aerosols entering the interior of the ASMA rise slowly and enter the stratosphere.

By enhancing the meridional transport in the UTLS region and lifting volcanic aerosols across the tropopause, the ASM significantly changed the distribution of volcanic aerosols in the Northern Hemisphere, especially in Asia, and expanded the potential effects of volcanic eruptions.

The study was published in npj Climate and Atmospheric Science.

Citation: Wu, X. et al. The influence of the Asian summer monsoon on volcanic aerosol transport in the UTLS region. npj Clim Atmos Sci 6, 11 (2023). doi: https://doi.org/10.1038/s41612-023-00339-w

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