Impacts of Climate Change on Wildfire Dispersion in the Intermountain West

Recent research suggests an increase in western United States fire expanse will likely occur as temperatures rise in the coming decades. A recent uptick in decadal trends in fire expanse have already resulted in decreased air quality across the Intermountain West. As fire frequency and expanse further increase, the question remains as to how significantly regional air quality will be impacted. This question requires study of numerous aspects of climate change, including regional near-surface thermodynamic trends, fire-related emissions, and climatological synoptic flow patterns.

The current study will utilize data from the Coupled Model Intercomparison Phase 5 (CMIP5) climate assessment to infer impacts of future wildfires on regional and local air quality. Future wildfire emissions will be derived using a combination of the most recent Global Fire Emissions Database (GFED4) with recent literature prognostications of wildfire expanse increases (e.g. that of Spracklen et al. [Journal of Geophysical Research, 114, 30613–30650, 2009]). Given that the study will emphasize impacts of climatological large-scale flow patterns, the kinematic field will be statically established using assimilation of CMIP5 output into WRF Chem. Temporal averages of GFED4 emissions estimates from 2000-2015 will be modified using simple coefficients from estimates of fire expanse increases, as provided by recently influential literature. Both the CMIP5 and GFED4 data will be downscaled to an approximately 4km x 4km grid to ensure impacts of regional topography are resolved. While climatological averages in kinematic profiles may not be applicable to analysis of specific events (i.e. acute exposure), they may provide mean-state conditions of aerosol concentrations (i.e. chronic exposure).

The results of this research are relevant to air quality and influences of wildfire-borne aerosols on downstream cloud and ecological impacts. Recent research has suggested aerosols to be influential on both severe storm and general convective cloud development. The link between aerosols and asthmatic symptoms has been well established, with potential indications for development of long-term respiratory diseases.