Simulation of a biomass-burning plume: Comparison of model results with observations

[1] We have simulated the dynamical evolution of the plume from a prescribed biomass fire, using the active tracer high- resolution atmospheric model (ATHAM). Initialization parameters were set to reflect the conditions during the fire. The model results are compared with airborne remote-sensing and in situ measurements of the plume. ATHAM reproduces the injection height (250-600 m) and the horizontal extent of the plume (similar to4 km) with good accuracy. The aerosol mass concentrations are underestimated but still in the range of the observations. Remaining differences between the model results and the measurements are attributed to limited meteorological and fire emission information. Additionally, radiative transfer simulations using in situ measurements of the aerosol properties are performed. A comparison of the measured and simulated reflected solar flux shows an underestimation by the model over the ocean surface, which is most likely due to an underestimation of the aerosol optical depth in the model. The instantaneous radiative forcing was calculated to -36 W m(-2) over land and 5-8 W m(-2) over the ocean for a solar zenith angle of 47degrees and an optical depth of unity, consistent with previous studies. Overall, it appears that ATHAM is a valuable tool for the examination of transport processes within biomass-burning plumes and, together with a chemical and microphysical module, is suitable for studies of the interaction between transport, chemistry, and microphysics within such plumes