Aerosol dispersion in the boundary layer after autumnal frontal passages in Central London and Suburban Oklahoma

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Sunday, 17 January 2010
Exhibit Hall B2 (GWCC)
Margaret Frey, ILREUM, Norman, OK

The study of urban boundary layer dynamics in correspondence with weather events is important in diagnosing day-to-day air quality variations. The boundary layer is often characterized by random eddies that result in turbulent flow. Measurements from atop the National Weather Center in Norman, OK provide a unique perspective on boundary layer dynamics. Data from two sonic anemometers is used to quantify the change in turbulence kinetic energy and momentum fluxes, and, ultimately, the boundary layer structure, with frontal passages in October, 2008. The turbulent eddy variation around the anemometers yielded a unique perspective on this atmospheric mixing. A comparison is made with frontal passages in November, 2007 in Central London, England. The Universities' Facilities for Atmospheric Measurements (UFAM) under the United Kingdom's National Centre for Atmospheric Research conducted the REPARTEE_II campaign using a Doppler lidar to study urban boundary layer structure. The lidar was placed in Central London directly south of Regent's Park. The raw data is analyzed for variations in vertical velocity and turbulent shear. The lidar backscatter realistically depicts the vertical structure and aerosol dispersion throughout the boundary layer. Days after the frontal passages indicate a daytime well-mixed layer and have less convective turbulence, similar to the conclusions atop the National Weather Center. The site location in London is the ideal urban environment and provides evidence of air particle dispersion corresponding to frontal passages. After frontal passages, the boundary layer in London allowed for more aerosol mixing. Lidars are a powerful tool and are particularly helpful in recognizing aerosol dispersion because the full vertical profile is illustrated. Boundary layer profiles in these two urban scenarios can assist in tracking the distribution of pollutants, specifically in accordance with certain weather events. As atmospheric pollution is increasingly quantified it is necessary to track aerosol movement in congruence with weather changes; this will assist in the prediction of local air quality reports throughout the lower atmosphere.