Validation of the Gaussian Plume Model AEROPOL model against the Cabauw Field Experiment.

Abstract: The Gaussian dispersion model AEROPOL is validated against the Cabauw (1977 – 1978) data set, applying the parameters and rules described in the Model Validation Kit. The purpose to revisit this classical experiment is preparation for fast response to elevated (buoyant) accidental releases. In the AEROPOL model (Kaasik & Kimmel, 2003) two alternatives for dispersion parameterisations are used: (i) classical Pasquill-Gifford stability and (ii) a scheme based on Lagrangian time scales by Gryining et al. (1987). Validation is based on correlation, fractional bias, fractional sigma, NMSE and fraction in factor 2, applying these statistics to maximal arc-wise, near-centreline and cross-wind integrated concentrations. Both parameterisations are found fairly adequate. The Pasquill-Gifford parameterisation performs somewhat better, except for correlations, which exceed even 0.9 with Gryning scheme. The Gryning scheme results in too wide Gaussian spread and thus, in lower maxima compared to measurements, whereas the Pasquill parameterisation gives sharper maxima, which makes the statistics more sensitive to small discrepancies in plume position. The average between the lowest measurement level and release level wind speed and direction is found to be a good approximation for the effective wind according to the position of Gaussian plume.