Supplementary material to "Modelling the aerosol chemical composition of the tropopause over the Tibetan Plateau during the Asian summer monsoon"

Abstract. Enhanced aerosol abundance in the upper troposphere and lower stratosphere (UTLS) associated with the Asian summer monsoon (ASM), is referred to as the Asian Tropopause Aerosol Layer (ATAL). The chemical composition, microphysical properties and climate effects of aerosols in the ATAL have been the subject of discussion over the past decade. In this work, we use the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model at a relatively fine grid resolution (about 1.1 × 1.1 degrees) to numerically simulate the emissions and chemistry of aerosols and their precursors in the UTLS within the ASM anticyclone during the years 2010–2012. We find a pronounced maximum in aerosol extinction in the UTLS over the Tibetan Plateau, which to a large extent is caused by mineral dust emitted from the northern Tibetan Plateau and slope areas, lofted to an altitude of at least 10 km, and accumulating within the anticyclonic circulation. Our simulations show that mineral dust, water soluble compounds, such as nitrate and sulfate, and associated liquid water dominate aerosol extinction in the UTLS within the ASM anticyclone. Due to shielding of high background sulfate concentrations outside the anticyclone from volcanoes, a relative minimum of aerosol extinction within the anticyclone in the lower stratosphere is simulated, being most pronounced in 2011 when the Nabro eruption occurred. In contrast to mineral dust and nitrate concentrations, sulfate increases with increasing altitude due to the larger volcano effects in the lower stratosphere compared to the upper troposphere. Our study indicates that the UTLS over the Tibetan Plateau can act as a well-defined conduit for natural and anthropogenic gases and aerosols into the stratosphere.

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Modeling the aerosol chemical composition of the tropopause over the Tibetan Plateau during the Asian summer monsoon

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-11587-2019 ◽

2019 ◽

Vol 19 (17) ◽

pp. 11587-11612 ◽

Cited By ~ 9

Author(s):

Jianzhong Ma ◽

Christoph Brühl ◽

Qianshan He ◽

Benedikt Steil ◽

Vlassis A. Karydis ◽

...

Keyword(s):

Chemical Composition ◽

Tibetan Plateau ◽

Summer Monsoon ◽

Lower Stratosphere ◽

Mineral Dust ◽

Asian Summer Monsoon ◽

The Tibetan Plateau ◽

Aerosol Extinction ◽

Upper Troposphere ◽

Asian Summer

Abstract. Enhanced aerosol abundance in the upper troposphere and lower stratosphere (UTLS) associated with the Asian summer monsoon (ASM) is referred to as the Asian Tropopause Aerosol Layer (ATAL). The chemical composition, microphysical properties, and climate effects of aerosols in the ATAL have been the subject of discussion over the past decade. In this work, we use the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model at a relatively fine grid resolution (about 1.1×1.1∘) to numerically simulate the emissions, chemistry, and transport of aerosols and their precursors in the UTLS within the ASM anticyclone during the years 2010–2012. We find a pronounced maximum of aerosol extinction in the UTLS over the Tibetan Plateau, which to a large extent is caused by mineral dust emitted from the northern Tibetan Plateau and slope areas, lofted to an altitude of at least 10 km, and accumulating within the anticyclonic circulation. We also find that the emissions and convection of ammonia in the central main body of the Tibetan Plateau make a great contribution to the enhancement of gas-phase NH3 in the UTLS over the Tibetan Plateau and ASM anticyclone region. Our simulations show that mineral dust, water-soluble compounds, such as nitrate and sulfate, and associated liquid water dominate aerosol extinction in the UTLS within the ASM anticyclone. Due to shielding of high background sulfate concentrations outside the anticyclone from volcanoes, a relative minimum of aerosol extinction within the anticyclone in the lower stratosphere is simulated, being most pronounced in 2011, when the Nabro eruption occurred. In contrast to mineral dust and nitrate concentrations, sulfate increases with increasing altitude due to the larger volcano effects in the lower stratosphere compared to the upper troposphere. Our study indicates that the UTLS over the Tibetan Plateau can act as a well-defined conduit for natural and anthropogenic gases and aerosols into the stratosphere.

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Transport of Asian surface pollutants to the global stratosphere from the Tibetan Plateau region during the Asian summer monsoon

National Science Review ◽

10.1093/nsr/nwaa005 ◽

2020 ◽

Vol 7 (3) ◽

pp. 516-533 ◽

Cited By ~ 4

Author(s):

Jianchun Bian ◽

Dan Li ◽

Zhixuan Bai ◽

Qian Li ◽

Daren Lyu ◽

...

Keyword(s):

Tibetan Plateau ◽

Summer Monsoon ◽

Asian Summer Monsoon ◽

Global Climate ◽

Pollutant Emissions ◽

The Tibetan Plateau ◽

Plateau Region ◽

Radiative Processes ◽

Asian Summer ◽

The Impact

Abstract Due to its surrounding strong and deep Asian summer monsoon (ASM) circulation and active surface pollutant emissions, surface pollutants are transported to the stratosphere from the Tibetan Plateau region, which may have critical impacts on global climate through chemical, microphysical and radiative processes. This article reviews major recent advances in research regarding troposphere–stratosphere transport from the region of the Tibetan Plateau. Since the discovery of the total ozone valley over the Tibetan Plateau in summer from satellite observations in the early 1990s, new satellite-borne instruments have become operational and have provided significant new information on atmospheric composition. In addition, in situ measurements and model simulations are used to investigate deep convection and the ASM anticyclone, surface sources and pathways, atmospheric chemical transformations and the impact on global climate. Also challenges are discussed for further understanding critical questions on microphysics and microchemistry in clouds during the pathway to the global stratosphere over the Tibetan Plateau.

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