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Particulate sulfur in the upper troposphere and lowermost stratosphere - Sources and climate forcing

Martinsson, Bengt G. LU ; Friberg, Johan LU ; Elmqvist Sandvik, Oscar LU ; Hermann, Markus; van Velthoven, Peter F. J. and Zahn, Andreas (2017) In Atmospheric Chemistry and Physics 17(18). p.10937-10953
Abstract

This study is based on fine-mode aerosol samples collected in the upper troposphere (UT) and the lowermost stratosphere (LMS) of the Northern Hemisphere extratropics during monthly intercontinental flights at 8.8-12 km altitude of the IAGOS-CARIBIC platform in the time period 1999-2014. The samples were analyzed for a large number of chemical elements using the accelerator-based methods PIXE (particle-induced X-ray emission) and PESA (particle elastic scattering analysis). Here the particulate sulfur concentrations, obtained by PIXE analysis, are investigated. In addition, the satellite-borne lidar aboard CALIPSO is used to study the stratospheric aerosol load. A steep gradient in particulate sulfur concentration extends several... (More)

This study is based on fine-mode aerosol samples collected in the upper troposphere (UT) and the lowermost stratosphere (LMS) of the Northern Hemisphere extratropics during monthly intercontinental flights at 8.8-12 km altitude of the IAGOS-CARIBIC platform in the time period 1999-2014. The samples were analyzed for a large number of chemical elements using the accelerator-based methods PIXE (particle-induced X-ray emission) and PESA (particle elastic scattering analysis). Here the particulate sulfur concentrations, obtained by PIXE analysis, are investigated. In addition, the satellite-borne lidar aboard CALIPSO is used to study the stratospheric aerosol load. A steep gradient in particulate sulfur concentration extends several kilometers into the LMS, as a result of increasing dilution towards the tropopause of stratospheric, particulate sulfur-rich air. The stratospheric air is diluted with tropospheric air, forming the extratropical transition layer (ExTL). Observed concentrations are related to the distance to the dynamical tropopause. A linear regression methodology handled seasonal variation and impact from volcanism. This was used to convert each data point into stand-alone estimates of a concentration profile and column concentration of particulate sulfur in a 3 km altitude band above the tropopause. We find distinct responses to volcanic eruptions, and that this layer in the LMS has a significant contribution to the stratospheric aerosol optical depth and thus to its radiative forcing. Further, the origin of UT particulate sulfur shows strong seasonal variation. We find that tropospheric sources dominate during the fall as a result of downward transport of the Asian tropopause aerosol layer (ATAL) formed in the Asian monsoon, whereas transport down from the Junge layer is the main source of UT particulate sulfur in the first half of the year. In this latter part of the year, the stratosphere is the clearly dominating source of particulate sulfur in the UT during times of volcanic influence and under background conditions.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Atmospheric Chemistry and Physics
volume
17
issue
18
pages
17 pages
publisher
Copernicus Gesellschaft Mbh
external identifiers
  • scopus:85029512362
  • wos:000410778000002
ISSN
1680-7316
DOI
10.5194/acp-17-10937-2017
language
English
LU publication?
yes
id
ba8aabf3-fdce-4991-b889-30e633210afb
date added to LUP
2017-09-29 11:50:31
date last changed
2018-01-16 13:20:01
@article{ba8aabf3-fdce-4991-b889-30e633210afb,
  abstract     = {<p>This study is based on fine-mode aerosol samples collected in the upper troposphere (UT) and the lowermost stratosphere (LMS) of the Northern Hemisphere extratropics during monthly intercontinental flights at 8.8-12 km altitude of the IAGOS-CARIBIC platform in the time period 1999-2014. The samples were analyzed for a large number of chemical elements using the accelerator-based methods PIXE (particle-induced X-ray emission) and PESA (particle elastic scattering analysis). Here the particulate sulfur concentrations, obtained by PIXE analysis, are investigated. In addition, the satellite-borne lidar aboard CALIPSO is used to study the stratospheric aerosol load. A steep gradient in particulate sulfur concentration extends several kilometers into the LMS, as a result of increasing dilution towards the tropopause of stratospheric, particulate sulfur-rich air. The stratospheric air is diluted with tropospheric air, forming the extratropical transition layer (ExTL). Observed concentrations are related to the distance to the dynamical tropopause. A linear regression methodology handled seasonal variation and impact from volcanism. This was used to convert each data point into stand-alone estimates of a concentration profile and column concentration of particulate sulfur in a 3 km altitude band above the tropopause. We find distinct responses to volcanic eruptions, and that this layer in the LMS has a significant contribution to the stratospheric aerosol optical depth and thus to its radiative forcing. Further, the origin of UT particulate sulfur shows strong seasonal variation. We find that tropospheric sources dominate during the fall as a result of downward transport of the Asian tropopause aerosol layer (ATAL) formed in the Asian monsoon, whereas transport down from the Junge layer is the main source of UT particulate sulfur in the first half of the year. In this latter part of the year, the stratosphere is the clearly dominating source of particulate sulfur in the UT during times of volcanic influence and under background conditions.</p>},
  author       = {Martinsson, Bengt G. and Friberg, Johan and Elmqvist Sandvik, Oscar and Hermann, Markus and van Velthoven, Peter F. J. and Zahn, Andreas},
  issn         = {1680-7316},
  language     = {eng},
  month        = {09},
  number       = {18},
  pages        = {10937--10953},
  publisher    = {Copernicus Gesellschaft Mbh},
  series       = {Atmospheric Chemistry and Physics},
  title        = {Particulate sulfur in the upper troposphere and lowermost stratosphere - Sources and climate forcing},
  url          = {http://dx.doi.org/10.5194/acp-17-10937-2017},
  volume       = {17},
  year         = {2017},
}