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| Titel |
South East Pacific atmospheric composition and variability sampled along 20° S during VOCALS-REx |
| VerfasserIn |
G. Allen, H. Coe, A. Clarke, C. Bretherton, R. Wood, S. J. Abel, P. Barrett, P. Brown, R. George, S. Freitag, C. McNaughton, S. Howell, L. Shank, V. Kapustin, V. Brekhovskikh, L. Kleinman, Y.-N. Lee, S. Springston, T. Toniazzo, R. Krejci, J. Fochesatto, G. Shaw, P. Krecl, B. Brooks, G. McMeeking, K. N. Bower, P. I. Williams, J. Crosier, I. Crawford, P. Connolly, J. D. Allan, D. Covert, A. R. Bandy, L. M. Russell, J. Trembath, M. Bart, J. B. McQuaid, J. Wang, D. Chand |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 11 ; Nr. 11, no. 11 (2011-06-01), S.5237-5262 |
| Datensatznummer |
250009800
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| Publikation (Nr.) |
 copernicus.org/acp-11-5237-2011.pdf |
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| Zusammenfassung |
| The VAMOS Ocean-Cloud-Atmosphere-Land Regional Experiment (VOCALS-REx) was conducted from
15 October to 15 November 2008 in the South East Pacific (SEP) region to investigate interactions
between land, sea and atmosphere in this unique tropical eastern ocean environment and to
improve the skill of global and regional models in representing the region. This study
synthesises selected aircraft, ship and surface site observations from VOCALS-REx to
statistically summarise and characterise the atmospheric composition and variability of the
Marine Boundary Layer (MBL) and Free Troposphere (FT) along the 20° S parallel
between 70° W and 85° W. Significant zonal gradients in mean MBL
sub-micron aerosol particle size and composition, carbon monoxide, sulphur dioxide and ozone
were seen over the campaign, with a generally more variable and polluted coastal environment
and a less variable, more pristine remote maritime regime. Gradients in aerosol and trace gas concentrations were observed to be
associated with strong gradients in cloud droplet number. The FT was often more polluted in
terms of trace gases than the MBL in the mean; however increased variability in the FT
composition suggests an episodic nature to elevated concentrations. This is consistent with
a complex vertical interleaving of airmasses with diverse sources and hence pollutant
concentrations as seen by generalised back trajectory analysis, which suggests contributions
from both local and long-range sources. Furthermore, back trajectory analysis demonstrates
that the observed zonal gradients both in the boundary layer and the free troposphere are
characteristic of marked changes in airmass history with distance offshore – coastal
boundary layer airmasses having been in recent contact with the local land surface and
remote maritime airmasses having resided over ocean for in excess of ten days. Boundary
layer composition to the east of 75° W was observed to be dominated by coastal
emissions from sources to the west of the Andes, with evidence for diurnal pumping of the
Andean boundary layer above the height of the marine capping inversion. Analysis of intra-campaign variability
in atmospheric composition was not found to be significantly correlated with observed low-frequency variability
in the large scale flow pattern; campaign-average interquartile ranges of CO, SO2 and O3
concentrations at all longitudes were observed to dominate over much smaller differences in median
concentrations calculated between periods of different flow regimes.
The campaign climatology presented here aims to provide a valuable dataset to inform model simulation and future
process studies, particularly in the context of aerosol-cloud interaction and further
evaluation of dynamical processes in the SEP region for conditions analogous to those during
VOCALS-REx. To this end, our results are discussed in terms of coastal, transitional
and remote spatial regimes in the MBL and FT and a gridded dataset are provided as a resource. |
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