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

Abstract

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 period of sustained light winds, which included humid sea breezes and land breezes. The first event occurred early in the period when the atmospheric circulation involved either weak sea breezes or no sea breeze at the coast. Described here are the meteorological conditions associated with the inter-regional transport of smoke from a prescribed, or hazard reduction, burn just north of Sydney, which concentrated smoke in the eastern part of the Sydney metropolitan area. The second event, which occurred late in the episode, was 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 highway. Also described are the meteorological conditions that contributed to the disruption of a major highway caused by a multiple vehicle pile-up just to the south-west of Sydney later in the period. Numerical model simulations using the University of New South Wales (UNSW) NWP model, which used archived real-time data, accurately predicted both the concentration of pollution in the eastern part of the Sydney metropolitan area in the first event and the hazardous smog formation and timing of the clearing south-west wind change in the second event.