Vertical radon-222 profiles in the atmospheric boundary layer
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Date
2011-11-15
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Publisher
CSIRO and the Bureau of Meteorology
Abstract
Radon-222 (radon) is a naturally occurring radioactive tracer of air mass transport on different time and space scales. In particular, the vertical distribution of radon has been demonstrated to be useful for characterisation of exchange and mixing processes within the atmospheric boundary layer.
In 2006 we started a program of research, using radon-222 to advance our understanding of these processes as part of a broader goal to improve parameterisation schemes for vertical mixing in the lower atmosphere. Two types of experiments have been conducted. The first is based on continuous hourly estimates of radon-222 concentration gradients at two meteorological towers, one focussing on near-surface gradients (2-50m) recorded on a 50m tower at Lucas Heights in New South Wales (34.05ºS, 150.98ºE), and the other on boundary layer gradients (20-200 m) measured on a 213m tower at the Cabauw Experimental Site for Atmospheric Research in the Netherlands (51.971ºN, 4.927ºE). The second experiment type relies on the collection of high resolution radon-222 vertical profiles up to 4,000 m above ground level using radon samplers mounted on an instrumented motorised research glider.
In this presentation, we discuss selected results from a unique set of high resolution vertical radon profiles measured in 2007-2010 in clear and cloudy daytime terrestrial boundary layers over rural New South Wales. The profile examples reveal the characteristic structure and variability of three major types of daytime boundary layer: 1) dry convective boundary layers,
2) mixed layers topped with residual layers, and 3) convective boundary layers topped with coupled non-precipitating clouds. We demonstrate that important boundary layer processes are identifiable in the observed radon profiles, including ‘‘top down’’ mixing associated with entrainment in clear-sky cases and strongly enhanced venting and sub-cloud layer mixing when
substantial active cumulus are present.
A related presentation (Chambers et al. 2011) outlines some recent results based on our radon gradient measurements at the Lucas Heights tower. © 2011 CSIRO and the Bureau of Meteorology.
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Keywords
Radon 222, Boundary layers, Australia, Netherlands, Surface air, Earth atmosphere
Citation
Zahorowski, W., Williams, A. G., Chambers, S., Griffiths, A., Crawford, J., Werczynski, S., & Element, A. (2011). Vertical radon-222 profiles in the atmospheric boundary layer. Presentation to the the CAWCR Workshop 15 November - 17 November 2011, Melbourne, Australia, (pp. 98).