Regional Air Pollution Impacts of Biomass Fires: Sensitivity to Uncertainties in Fuel Consumption and Fire Plume Dynamics

Biomass fires emit large amounts of trace gases and aerosols and these emissions are believed to significantly influence the chemical composition of the atmosphere and the Earth's climate system. The air quality impact of biomass burning depends on meteorology, fire plume dynamics, biomass (fuel) consumed, the quantity and chemical composition of the emissions, and the atmosphere into which the emissions are dispersed. We examine the sensitivity of model predicted CO, PM2.5, and O3 concentration fields to uncertainties in fuel consumption and fire plume dynamics, focusing on the peak of the western United States wildfire season in late August, 2006. MODIS data for fire locations and burned areas, a vegetation map for the type of biomass burned, and an extensive emission factor database are combined with different models of fuel loading (FOFEM, FCCS) and fuel consumption (FOFEM, CONSUME) to derive a four member ensemble of hourly mass emission rates for 30 gas phase and aerosol species with spatial resolution of 1-km2. Uncertainties in fire plume dynamics are represented using two different plume rise models (Briggs, PLUMP) to prescribe the vertical distribution of fire emissions, yielding eight unique emission scenarios. The air quality impact of the fire emissions scenarios is assessed by assimilating the fire emissions, along with anthropogenic and biogenic emissions, into the WRF/Chem v2.2. model, which is run using a 22-km horizontal resolution CONUS domain.