Mason Research Group

Mason Research Group

Louise Wolfe, Dr. Sherri Mason, Lisa Carlson
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      Our current research project involves the development, comparison and evaluation of a biomass burning smoke plume model. The goal of the project is to compare simulated species concentrations to those measured in the field, as well as to those predicted by another independently created smoke plume model from the Max Planck Institute in Mainz, Germany. The focus of the project is upon sets of field measurements for two forest fires in very different fire environments, the African savanna and an Alaskan boreal forest. Initial work on this project started in January, 2003, and consisted of tailoring our biomass burning smoke plume model [e.g., Mason et al., 2001] to the specific smoke plumes of interest. The horizontal (cross-wind) diffusion coefficients were determined for each smoke plume using the observed initial smoke plume width and fitting the simulated CO and CO2 concentrations to field measurements taken immediately above (i.e., initial modeling conditions) and downwind (i.e., simulated concentration comparison points) of the forest fires. Louise Wolfe was the principal undergraduate supervisor of this first part of the project.
      Significant progress was made over the summer of 2003 with the financial support of a Merck/AAAS Undergraduate Summer Research Fellowship, awarded to Lisa Carlson. Using the determined horizontal diffusion coefficients to describe the dilution of the smoke plume, and additional field measurements taken immediately above the flaming front, including altitude, temperature, pressure, relative humidity and species concentrations (both ambient and those within the smoke plume), we developed smoke plume models for both the African and Alaskan forest fires. Our simulated species concentrations were then compared to those simulated by Drs. Joerg Trentmann and Tanja Winterrath at the Max Planck Institute in Mainz, Germany, using their independently created biomass burning smoke plume model and a common set of initial modeling conditions. Additionally we compared both of our modeling results to downwind smoke plume field measurements.
      In comparison to each other, our model tends to simulate higher radical species and peroxyacyl nitrate (PANs) concentrations, than does the Max Planck model. As tropospheric photochemistry involves the NOx-catalyzed oxidation of carbonaceous species via free radical intermediates, the concentrations of these species are central to understanding the processing state of the atmosphere. Hence, current work is aimed at understanding the differences between the models which lead to the observed differences in simulated species behavior. In comparison to the field measurements, while both models simulate the majority species concentrations fairly well (within experimental error), they also both dramatically underestimate ozone production within the African smoke plume. Additionally, while modeled ozone production within the Alaskan smoke plume compares well with the field measurements, the observed organic acid formation is not predicted by either smoke plume model. Both of these results seem to indicate that there is a deficiency within the modeled photochemistry.
      Both Lisa Carlson and Louise Wolfe are continuing work on this project during the 2003-2004 AY, with their primary research interests focused upon 1) understanding the differences in the models as compared to each other and 2) investigating the deficiencies of individual models in regard to their simulated species concentrations as compared to the field measurements. We will be presenting a poster describing this on-going research project at the American Geophysical Union fall meeting in December, 2003, and anticipate manuscript preparation to begin in the spring, 2004.