Modeling biomass burnings by coupling a sub-grid scale plume model with Adaptive Grid CMAQ

Biomass burning plumes are not well resolved in current air quality modeling systems due to insufficient grid resolution and/or inadequate sub-grid treatments. We developed a system that couples sub grid plume models and air quality models to enhance the ability to predict air quality impacts from biomass burnings. The air quality model used here is CMAQ and it uses adaptive grid method that increases grid resolutions to track the biomass burning plumes at the regional grid scales. Adaptive Grid CMAQ (AG-CMAQ) still requires precise burning emission inputs such as the plume's spatial spread and vertical profile at the sub-grid scale. Daysmoke is the Lagrangian plume model used to predict short range dispersion of prescribed burning plumes. When a biomass burning plume travels downwind and the plume resolution becomes compatible with the air quality model grid resolution, the plume concentrations are carried over to AG-CMAQ. The interface where the two models share their information is time dependent and is calculated and updated frequently in an analysis called “handover”. Handover is highly dependent on how well the grid resolution in the air quality model can capture the plume concentration gradient created in the plume model, Daysmoke. A sensitivity analysis was performed on three parameters that affect the cross sectional concentration distribution of a plume; 1) distance of the interface from the fire (5km, 8km, and varying distance currently used in Handover), 2) mass of a parcel used in Daysmoke (100g/parcel, 1kg/parcel), and 3) varying emission rate that is input to Daysmoke (1.5 times more emissions using the same burn area rate). Biomass burning simulations will be evaluated to show the impact of “handover” on the results of the coupled modeling system.