Mesoscale model forecasting as a tool for air pollution management: a casestudy of sustained smoke pollution over the Greater Sydney area

A mesoscale model has been applied over the Greater Sydney region to an air pollution episode resulting from fire hazard reduction burns from 12 to 14 April 1997. The episode was characterised by two distinct events in a peri od of sustained light winds, which included humid sea breezes and land bree zes. The first event occurred early in the period when the atmospheric circ ulation involved either weak sea breezes or no sea breeze at the coast. Des cribed here are the meteorological conditions associated with the inter-reg ional transport of smoke from a prescribed or hazard reduction, burn just n orth of Sydney, which concentrated smoke in the eastern part of the Sydney metropolitan area. The second event, which occurred late in the episode, wa s local in nature but was induced synoptically by the large-scale airflow, by a change in wind direction that transported smoke and fog over a major h ighway. Also described are the meteorological conditions that contributed t o the disruption of a major highway caused by a multiple vehicle pile-up ju st to the south-west of Sydney later in the period Numerical model simulati ons using the University of New South Wales (UNSW) NWP model, which used ar chived real-time data, accurately predicted both the concentration of pollu tion in the eastern part of the Sydney, metropolitan area in the first even t and the hazardous smog formation and tinting of the clearing south-west w ind change in the second event.