The sensitivity of smoke aerosol dispersion to smoke injection height and source-strength: a multi-model AeroCom study

The near-source and downwind impacts of smoke aerosols depend on both emitted mass and injection height. This study examines aerosol dispersion sensitivity to these factors using four global models from the AeroCom Phase III Biomass Burning Emission and Injection Height (BBEIH) experiment. Each model performed four simulations: BASE, using burned-area-based BB emissions GFED4.1s with default injection heights; BBIH, using monthly MISR plume injection heights; BBEM, using fire- radiative-power-based BB emission FEERv1.0; and NOBB, excluding BB emissions. The focus is the April 2008 Siberian wildfire event. Aerosol optical depth (AOD) varies across models. In BASE, all models show a steeper AOD decline from the source to downwind regions than satellite data, indicating inadequate long-range transport or excessive aerosol removal in all models. Moreover, near-source, most models overestimate aerosol extinction below 2 km, suggesting injection heights are too low. In BBIH, MISR plume injection heights slightly improve vertical aerosol distribution, but the magnitude is too small. In BBEM, AOD increases significantly near the source due to enhanced BB emissions; however, the downwind AOD remains largely underestimated in both BBIH and BBEM. Notably, CALIOP lidar reveals aerosol layers above 6 km from source to downwind regions – features absent in all model simulations, although a high bias in the gridded CALIOP data makes the evaluation inconclusive. These results suggest that monthly MISR plume injection heights and enhanced BB emissions alone are insufficient to resolve the model–observation discrepancies. Injecting smoke at higher altitudes in Siberia and reducing aerosol wet removal warrant further investigation.