In-situ data from Mt. Bachelor and MISR observations suggests that plume heights are a proxy for chemical composition of biomass plume

During 2008 large fires burned in Northern California and Western Oregon. Plumes from these fires resulted in large concentrations of CO and sub-micron aerosols at the Mt. Bachelor Observatory at 2.7 km in central Oregon. The CO and aerosol scattering levels we observed were the highest ever observed at the observatory, 2.8 ppmv and 1046 Mm-1, respectively. Overall aerosol scattering and CO were very well correlated throughout the summer fire season and in individual plume events. However the scattering/CO ratio varied dramatically in the individual plumes, from a low of 0,34 to a high of 0.72 Mm-1/ppbv. We evaluated whether this was due to aerosol removal or combustion conditions. Our analysis suggests that while there was dilution of the plumes during transport, removal of submicron aerosols was relatively minimal during the 1-2 day transit time to Mt. Bachelor, thus we conclude that the large change in observed chemical ratios reflects combustion processes. We further analyze these plumes using HYSPLIT trajectories and MODIS and MISR satellite data. The HYSPLIT trajectories allow us to identify the specific fires responsible for the high concentrations at Mt. Bachelor, while MODIS and MISR give information on the fire locations. In particular the MISR aerosol height product tells us about injection height of aerosol particles from the individual fires. From this analysis we found that higher injection heights are associated with lower scattering/CO ratios. This suggests that the MISR injection height may be a proxy for combustion conditions and emission ratios in fire plumes.