Validation of Gaussian Plume Model Aeropol against Cabauw Field Experiment

Abstract: The Gaussian dispersion model AEROPOL is validated against 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 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. Pasquill-Gifford parameterisation performs somewhat better, except for correlations, which exceed even 0,9 with Gryning scheme. Gryning scheme results in too wide Gaussian spread and thus, lower maxima compared to measurements, whereas the Pasquill parameterisation gives sharper maxima, which makes the statistics more sensitive to the small discrepancies in plume position. The average wind speed and direction between the lowest measurement level and release level was found a good approximation for effective wind according to position of Gaussian plume.