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The openair project » Examples of usage » Bivariate polar plots

Open Air Plume The bivariate polar plot (polarPlot) is a useful diagnostic tool for quickly gaining an idea of potential sources. Wind speed is one of the most useful variables to use to separate source types (see references).

For example, ground-level concentrations resulting from buoyant plumes from chimney stacks tend to peak under higher wind speed conditions. Conversely, ground-level, non-buoyant plumes such as from road traffic, tend to have highest concentrations under low wind speed conditions. Other sources such as from aircraft engines also show differing characteristics by wind speed.

Furthermore, given the very flexible 'type' option in openair functions, it is very easy to generate plots by season, site and so on – the possibilities are enormous and can be tailored to the question at hand.

polarPlot(mydata, pollutant = 'so2', type = 'weekend')

Polar Plot

Polar Plotscreenshot

References

Please get in touch with David Carslaw if you would like to be sent a pdf of any of these papers.

Carslaw, D.C., Beevers, S.D, Ropkins, K and M.C. Bell (2006). Detecting and quantifying aircraft and other on-airport contributions to ambient nitrogen oxides in the vicinity of a large international airport. Atmospheric Environment. 40/28 pp 5424-5434.

Westmoreland, E.J., N. Carslaw, D.C. Carslaw, A. Gillah and E. Bates (2007). Analysis of air quality within a street canyon using statistical and dispersion modelling techniques. Atmospheric Environment. Vol. 41(39), pp. 9195-9205.

Tomlin, A., Smalley, R., Tate, J., Barlow, J., Belcher, S., Arnold, S., Dobre, A., Robins, A., 2009. A field study of factors influencing the concentrations of a traffic-related pollutant in the vicinity of a complex urban junction. Atmospheric Environment 43 (32), 5027 –5037.