Benchmarks for chemical transport models based on radon-derived stability assessment of urban air pollution
Loading...
Date
2015-07-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of New South Wales and Australian Nuclear Science and Technology Organisation
Abstract
A clearer understanding of the variability in pollution concentrations in urban regions is essential for improving the predictive abilities of chemical transport models as well as identifying the need for (and assessing the efficacy of) emission mitigation strategies. Near-surface pollutant concentrations are a complex function of many factors, including: source strengths and distribution, local meteorology and air chemistry. On short (sub-diurnal) timescales, the extent of the vertical column within which emissions mix usually has the largest influence on measured concentrations, and the depth of this mixing volume is in turn closely related to wind speed and the thermal stability of the ABL. Continuous hourly observations of the ubiquitous, surfaceemitted, passive tracer radon-222 provide a powerful alternative to contemporary meteorological techniques for assessing stability effects on urban pollutants, because radon's concentration is closely matched with pollution transport processes at the surface. Here we outline a technique by which single-height, near-surface (<20m) radon observations can be conditioned to derive a multi-category stability classification scheme for urban pollution monitoring to provide benchmarking tools for local- to regional- chemical transport model evaluations. Efficacy of the radon-based classification scheme is compared to that based on conventional Pasquil-Gifford "turbulence" and "radiation" schemes. Lastly, we provide benchmark values for the Sydney region of climatological parameters and some key urban pollutant emissions under stable atmospheric conditions, when air nearest the surface can completely decouple from the overlying atmosphere, and numerical models are renowned for their poorest performance.
Description
Keywords
Benchmarks, Chemicals, Radon, Urban areas, Air pollution, Stability
Citation
Chambers, S. & Williams A. G. (2015). Benchmarks for chemical transport models based on radon-derived stability assessment of urban air pollution. Presentation to the 13th Australasian Environment Isotope Conference (AEIC), Sydney, 8-10th July 2015.