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Towards a Universal “Baseline” Characterisation of Air Masses for High- and Low-Altitude Observing Stations Using Radon-222
JournalArticle (Originalarbeit in einer wissenschaftlichen Zeitschrift)
ID 3455691
Author(s) Chambers, Scott D.; Williams, Alastair G.; Conen, Franz; Griffith, Alan D.; Reimann, Stefan; Steinbacher, Martin; Krummel, Paul B.; Steele, L. Paul; van der Schoot, Marcel V.; Galbally, Ian E.; Molloy, Suzie B.; Barnes, John E.
Author(s) at UniBasel Conen, Franz
Year 2016
Title Towards a Universal “Baseline” Characterisation of Air Masses for High- and Low-Altitude Observing Stations Using Radon-222
Journal Aerosol and Air Quality Research
Volume 16
Number 3
Pages / Article-Number 885-899

We demonstrate the ability of atmospheric radon concentrations to reliably and unambiguously identify local and remote terrestrial influences on an air mass, and thereby the potential for alteration of trace gas composition by anthropogenic and biogenic processes. Based on high accuracy (lower limit of detection 10–40 mBq m–3), high temporal resolution (hourly) measurements of atmospheric radon concentration we describe, apply and evaluate a simple two-step method for identifying and characterising constituent mole fractions in baseline air. The technique involves selecting a radon-based threshold concentration to identify the “cleanest” (least terrestrially influenced) air masses, and then performing an outlier removal step based on the distribution of constituent mole fractions in the identified clean air masses. The efficacy of this baseline selection technique is tested at three contrasting WMO GAW stations: Cape Grim (a coastal low-altitude site), Mauna Loa (a remote high-altitude island site), and Jungfraujoch (a continental high-altitude site). At Cape Grim and Mauna Loa the two-step method is at least as effective as more complicated methods employed to characterise baseline conditions, some involving up to nine steps. While it is demonstrated that Jungfraujoch air masses rarely meet the baseline criteria of the more remote sites, a selection method based on a variable monthly radon threshold is shown to produce credible “near baseline” characteristics. The seasonal peak-to-peak amplitude of recent monthly baseline CO2 mole fraction deviations from the long-term trend at Cape Grim, Mauna Loa and Jungfraujoch are estimated to be 1.1, 6.0 and 8.1 ppm, respectively.

Publisher Taiwan Association for Aerosol Research (TAAR)
ISSN/ISBN 1680-8584 ; 2071-1409
Full Text on edoc No
Digital Object Identifier DOI 10.4209/aaqr.2015.06.0391
ISI-Number WOS:000371498900033
Document type (ISI) Article

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