This project will investigate the impacts of boreal fire emissions since 1997 on trace gases and aerosols in the troposphere. Large boreal fires in recent years caused large perturbations to the atmospheric abundance of carbon monoxide and aerosols, with effects on nitrogen oxides and ozone as well. A three-dimensional model of atmospheric chemistry and transport (GEOS-Chem) will be used to analyze the hemispheric-scale impacts of these fires. Model simulations will be driven by assimilated meteorological fields to allow for interannual variability in transport. This work will employ two independently derived monthly emissions inventories of gas and aerosol species for boreal fires. A key uncertainty in quantifying the effects of boreal fire emissions is lack of knowledge of the heights at which the emissions are injected into the atmosphere. Data from the Multi-angle Imaging SpectroRadiometer (MISR) on board the Terra spacecraft will be analyzed to determine the injection heights of emissions from Siberian fires since 2000, and to relate the heights to area burned, fuel consumed, and prevailing meteorology. The model simulations will be evaluated with measurements of gases from surface stations, and from remote sensing, including Measurements of Pollution In The Troposphere (MOPITT) data for carbon monoxide (CO) and moderate resolution imaging spectroradiometer (MODIS) data for aerosols. Data for the areas of fires, fuel loading, and emission factors will be used to reconcile bottom-up estimates of fire emissions with constraints imposed by the results of the 3-d model calculations and atmospheric observations. The aerosol distributions (black carbon and organic carbon) and resulting aerosol optical depths from the boreal fires will be used to calculate the instantaneous radiative forcing for extreme fires years compared to low fire years. Understanding the impacts of emissions from these fires is required to determine the role that natural processes play in causing degradation of air quality in the United States and elsewhere, and in influencing climate.
This project will support a post-doctoral student. Participants in this research will be focusing on the broader implications of this work by participating in professional meetings and though interactions with colleagues from other disciplines.
