Preprints
https://doi.org/10.5194/acp-2021-910
https://doi.org/10.5194/acp-2021-910
 
03 Dec 2021
03 Dec 2021
Status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Exploring the inorganic composition of the Asian Tropopause Aerosol Layer using medium-duration balloon flights

Hazel Vernier1, Neeraj Rastogi2, Hongyu Liu3,4, Amit Kumar Pandit3, Kris Bedka4, Anil Patel2, Madineni Venkat Ratnam5, Buduru Suneel Kumar6, Bo Zhang3, Harish Gadhavi2, Frank G. Wienhold7, Gwenael Berthet1, and Jean-Paul Vernier3,4 Hazel Vernier et al.
  • 1Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E), France
  • 2Physical Research Laboratory, Ahmedabad, India
  • 3National Institute of Aerospace, Hampton, VA, USA
  • 4NASA Langley Research Center, Hampton, VA, USA
  • 5National Atmospheric Research Laboratory, Gadanki, India
  • 6TIFR Balloon Facility, Hyderabad, India
  • 7ETH, Zürich, Switzerland

Abstract. Satellite observations have revealed an enhanced aerosol layer near the tropopause over Asia during the summer monsoon, called the Asian Tropopause Aerosol Layer (ATAL). In this work, aerosol particles in the ATAL were collected with a balloon-borne impactor near the tropopause region over India, using extended duration balloon flights, in summer 2017 and winter 2018. Their chemical composition was further investigated by quantitative analysis using offline ion chromatography. Nitrate (NO3) and nitrite (NO2) were found to be the dominant ions in the collected aerosols with values ranging between 87–343 ng/m3 STP during the summer campaign. In contrast, sulfate (SO42−) levels were found above the detection limit (> 10 ng/m3 STP) only in winter. In addition, we determined the origin of the air masses sampled during the flights through analysis of back trajectories along with convective influence. The results obtained therein were put into a context of large-scale transport and aerosol distribution with GEOS-Chem chemical transport model simulations. The first flight of summer 2017 which sampled air mass within the Asian monsoon anticyclone (AMA), influenced by convection over Western China, was associated with particle size radius (0.05–2 μm). In contrast, the second flight sampled air mass at the edge of the AMA associated with larger particle size radius (> 2 μm) with higher nitrite concentration. The sampled air masses in winter 2018 were likely affected by smoke from the Pacific Northwest fire event in Canada, which occurred 7 months prior to our campaign, leading to concentration enhancements of SO42− and Ca2+. Overall, our results suggest that nitrogen-containing particles represent a large fraction of aerosols populating the ATAL, in agreement with the results from aircraft measurements during the StratoClim campaign. Furthermore, GEOS-Chem model simulations suggest that lightning NOx emissions had a significant impact on the production of nitrate aerosols sampled during the summer 2017.

Hazel Vernier et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-910', Anonymous Referee #1, 23 Dec 2021
  • RC2: 'Comment on acp-2021-910', Anonymous Referee #2, 29 Dec 2021
  • AC1: 'Replies-to-reviewers', Hazel Vernier, 11 Apr 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-910', Anonymous Referee #1, 23 Dec 2021
  • RC2: 'Comment on acp-2021-910', Anonymous Referee #2, 29 Dec 2021
  • AC1: 'Replies-to-reviewers', Hazel Vernier, 11 Apr 2022

Hazel Vernier et al.

Hazel Vernier et al.

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Short summary
The chemical composition of the stratospheric aerosols collected onboard high-altitude balloons above the Summer Asian Monsoon reveals the presence of nitrate/nitrite. Using numerical simulations and satellite observations, we found that pollution as well as lightinning could explain some of our observations.
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