UDINEE: Evaluation of multiple models with data from the JU2003 puff releases in Oklahoma City. Part II: Simulation of puff parameters

Abstract

The capabilities of nine atmospheric dispersion models (ADMs) in predicting near-field dispersion from puff releases in an urban environment have been addressed under the Urban Dispersion INternational Evaluation Exercise (UDINEE) project. The models’ results have been evaluated using tracer observations from the Joint Urban 2003 (JU2003) experiment where neutrally buoyant puffs were released in the downtown of Oklahoma City. Sulphur hexafluoride (SF6) concentration time series measured at ten sampling locations during four daytime and four nighttime puff releases were used in this paper to evaluate how the models simulate the puff passage at the measurement locations. The neutrally buoyant puff releases in JU2003 are the closest scenario to Radiological Dispersal Device (RDD) releases in urban areas, and therefore, UDINEE is a first step towards the better emergency response to an RDD event in urban environments. We have investigated for each puff and sampler the models’ capability of simulating the peak concentration; the peak and puff arrival times; and time duration, defined as the time period over which concentrations exceeds the 10 % of the peak concentration. As expected, due to the highly transient nature associated with puff releases, this quantitative comparison has pointed out differences among the individual model performances on simulating the puff dispersion. The results have also shown that the characteristics of the release site can impact the modelling of the initial puff size and the initial along downwind spread of the puff.