Some comparisons of lidar estimates of peak ground-level concentrations with the predictions of UK-ADMS

A pilot study has been made with a rapid-scanning backscatter Lidar to obtain maps of the concentration of aerosol from a power station plume as it dispersed to the ground. A series of measurements were made around High Marnham power station during 16–19 August 1994. These consisted both of near-ground horizontal scans and crosswind vertical scans. Peak ground-level concentrations were identified on 23 occasions of approximately 10 min averaging time, divided between 9 series of scans. The vertical scans provided 6 series where the plume had apparently been fully sampled, thus providing estimates of the aerosol flux for calibration of the ground-level concentrations. Meteorological data were available from a nearby TV Mast and from the U.K. Meteorological Office synoptic station at Coningsby. The dispersion of this elevated emission was simulated using the U.K.-Advanced Dispersion Modelling System (U.K.-ADMS, ver 2.0). Agreement was found to be satisfactory, though the predictions were rather sensitive to the meteorological data employed. It should be noted that, for statistical reasons, the ensemble maximum ground-level concentration predicted by the model will normally be less than that found by seeking the maximum over a particular realization. The model was generally successful in predicting the distance within which the plume dispersed to the ground.