The Effect of the Urban Parametrization on Simulated Contaminant Atmospheric Transport and Dispersion

Abstract

Urban atmospheric transport and dispersion are investigated through the simulation of hypothetical contaminant releases. The Weather Research and Forecasting (WRF) model is used to simulate a New York City heat event from 18–20 July 2013 using three different urban parametrizations and the Noah land-surface model, with simulation results reflecting the variations in the parametrization of urban drag and building-wake effects, leading to simulated ranges of 2 °C for the surface air temperature, 3 m s−1 for the surface wind speed, and 20° for the surface wind direction. The Quick Urban and Industrial Complex (QUIC) model for atmospheric transport and dispersion is used to simulate three hypothetical contaminant releases in Central Park in New York City: the release of a biological agent from a backpack sprayer, the release of pressurized liquid chlorine from a rupture in a tanker truck, and the release of a radioisotope from a radiological dispersion device. The WRF model results from the four simulations at the times of maximum and minimum surface air temperature are used to initialize the QUIC model, with the different urban parametrizations leading to differences in plume directions and contaminant contour areas of up to 33° and up to a factor of 2.1, respectively. The variation in the size of predicted contours at the toxicity threshold may influence emergency-response decisions, while the differences in the predicted plume direction may influence where emergency-response personnel are directed. The results support the development and deployment of the best urban parametrization scheme in a forecast model for predicting hazard areas.