Impacts of Climate Change on Wildfire Plume Dispersion: Planetary Boundary Layer Evolution

Wildfire occurrence within the Intermountain West of North America has been forecast to increase due to climate change.  However, the associated influences of climate change on wildfire plume dispersion have not been substantially quantified.  Wildfire plume dispersion is complicated by its dependence on the interactions between the plume itself and the atmosphere, requiring knowledge of both atmospheric profiles and the intra-plume characteristics.  Wildfire plumes are generally constrained to within the planetary boundary layer (PBL), although more vigorous plumes may be injected into the free troposphere.  Therefore, the quantification of climatic changes to the atmospheric boundary layer profile is crucial to the understanding of how wildfire plumes will be dispersed in a changing future climate.

To estimate climatic changes in atmospheric contributions to wildfire plume dispersion within the Intermountain West, we developed probability distribution functions (PDFs) of forecast changes to one-dimensional atmospheric profiles.  An ensemble of models from the CMIP5 archive was used, with only output on climate model levels used to ensure maximum grid resolution within the PBL.  Historical plume dispersion changes were analyzed using reanalysis data to determine any bias within the CMIP5 output.  The determined PDFs of future atmospheric profiles will subsequently be assimilated into the System for Atmospheric Modeling (SAM) large-eddy simulation (LES) model to quantify changes to wildfire plume dispersion.  This work will directly increase knowledge regarding PBL evolution within climate models, and has eventual implications for increased understanding of climatic trends in the dispersion of wildfire-borne aerosols within the PBL.