Using radon–222 to distinguish between vertical transport processes affecting trace gas measurements at Jungfraujoch in the Swiss Alps
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Date
2015-07-09
Journal Title
Journal ISSN
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Publisher
University of New South Wales and Australian Nuclear Science and Technology Organisation
Abstract
Several globally-significant trace gases are measured continuously at Jungfrajoch, a key baseline monitoring station in the Swiss Alps. Often this is with the aim of characterising trends in regional-to-hemispheric composition and fluxes. The site is high, 3 km above the surrounding plateau, and usually measures well-mixed air which has travelled far from emission sources. Having said that, there are also periods of rapid vertical transport which bring air from nearby valleys to the site. During these periods trace gas measurements no longer represent large scale conditions, so it is important to have a method which can detect them. Several distinct processes can drive vertical transport; on clear summer days, especially when winds are weak, thermally-driven upslope mountain winds (anabatic winds) are prevalent.
Using hourly radon-222 observations, we identified days with a strong local influence from the radon concentration and used the shape of the diurnal cycle to sort days according to the strength of anabatic winds. Radon is ideal as tracer of continental air masses because it is emitted from soil at a relatively constant rate, it is chemically inert, and decays with a half-life of 3.8 days. Because of its short half-life, radon concentrations are much lower in the free troposphere than in the boundary-layer air over land.
For comparable radon concentrations, anabatic wind days at Jungfraujoch are different from non-anabatic days in terms of the average wind speed, humidity, air temperature anomalies, and trace species; with implications for long term monitoring at mountain sites.
Description
Keywords
Radon 222, Environmental transport, Gases, Alps, Switzerland
Citation
Griffiths, A., Conen, F., Weingartner, E., Zimmermann, L., Chambers, S., Williams, A. G., & Steinbacher, M. (2015). Using radon–222 to distinguish between vertical transport processes affecting trace gas measurements at Jungfraujoch in the Swiss Alps. Presentation to the 13th Australasian Environment Isotope Conference (AEIC), Sydney, 8-10th July 2015. In 13th Australasian Environmental Isotope Conference, Sydney, Australia, 8-10th July 2015, Programme and Abstracts, (pp. 56).